Your Zero Is Off And You Don't Even Know It
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- Опубликовано: 27 сен 2024
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For hunting, cold bore zero is what matters. Shoot one shot every day and record its position. Compile about 10 and use that as your zero. Light profile barrels shift a lot and with very few shots in my experience.
I agree. It’s also valuable to know, whether your cold bore shot is different than the rest. Assume it is, unless you know otherwise.
I have a carbon barrel and I would never buy one again. It’s hard to get any kind of really good accuracy grouping unless you’re prepared to sit there all day. And forget about taking a shooting course because the amount of shots you need to take as specified time is infeasible with that type of barrel.
I’ve got a Savage ultralight with a carbon fiber barrel and it’s shooting 1/2” or better (on a 3 shot group).
I also have an Eric Cortina tuner brake on it, maybe that’s the difference?
I dont shoot hunting rifles much so Im assuming it may be more of an issue with the thinner barrels and such. On good heave match barrels I dont see cold bore shift. There is clean bore shift of course. Personally, after a good cleaning I will shoot 10 rounds or so to foul it up and leave it alone until accuracy starts to degrade. Rinse, repeat.. There was a time when i thought cold bore shift was happening and what i found out (for me) was that it was actually cold shooter. To test this i took another rifle with me each day and did my first 20 or so shots from that other rifle. Then i shot the rifle i had a recorded cold bore on. Amazingly enough, no shift. That made me realize i needed a lot more work on my body position mechanics. Others may have different experiences.
@@HazardousRob some are better than others for sure.
I shoot PRS and when I have a zeroed rifle in Indiana and go to Northern Michigan or Southern Indiana or even 2 hours west in Illinois the following day, I have to re-zero because sometimes it's still off even if your equipment is not loose. Temperature, barometric pressure, density altitude, all kinds of stuff can affect your zero from one day to the next.
Have you tried the 4dof zero range function? I've been meaning to see if that works. I didn't realize what it was til recently.
What scope are you running?
@cijetovina You are correct! I had to look at my 4dof. Apparently, my memory sucks.
@patrioticguy1791 A rifle is never zeroed. Also the change of light will affect your pint of impact.
For sure it depends on what your goals are on hitting a target.
Spot on about temperature, barometric pressure and altitude!!!
you, as well as others in the comments hit the nail on the head, that a cold bore shot is the most important to care about if you’re hunting. I’ll add to that thought. Here in maine, it’s common for guys to go zero a rifle in the middle of august when it’s 90 degrees and humid. they say, “yup we’re good.” throw it in the corner until November. then they get up in a treestand when it’s 15 degrees and dry. even if it was a “cold bore” zero back in august, that’s a 75-80 degree difference even on the first shot, not to mention how much the humidity difference has on a traditional wood frame. a lot of us are familiar with finished wood doors not closing correctly in the summer when it’s hot and humid, but working correctly most other days. combine that with an 80 degree colder barrel on the first shot, you definitely could be off. I tested this theory with my 1968 .270 win model 70. Zeroed it from a rest on a hot humid day. went out the next similar weather day and put 2 rounds through it to simulate cold bore. both shots were within 1 Moa at about 75 yards. 5 more shots, barrel was warm, not a whole ton of change. went up to about 1.5moa which could have been shooter error or temp change. but in those 7 shots across a 10 minute interval, the barrel temp increased only 40 degrees. few months later, picked a 13 degree frosty morning, let the rifle sit in the cold truck all night. first 3 shots, all closely grouped, about 1 moa, but were all off about 3-4” from the point of aim at 75 yards. after 6 shots, the barrel was up to 70-80 degrees and we’re back within an inch of the point of aim. So that resting temp change, a 200 yard first shot on a deer, would have been off 7-10” compared to a 90 degree humid day.
I totally agree with you in that everyone wants to focus on group size, but none of that matters especially in a hunting rifle if it can't consistently hold zero.
One point not mentioned is if you wear glasses. This can impact your parallaxes without realizing.
I never realized cold bore issues with my Model 70 or my Blazer. This usually is a thing with extremely thin barrels e.g. Kimber from my experience or can be caused by a barrel with improper stress relief due to incorrect heat treatment which should very very rare.
I like the turret stickers.
Cold bore is very real. The velocity on that first shot is different than the subsequent shots. You can let the rifle cool completely and shoot again... only to find that even though the bore/barrel is stone cold, there is no shift in impact. Go out the next day or next weekend, and the cold bore shift is back. This leads me to believe that the cold bore phenomenon has more to do with chemical changes in the fouling in the bore. We know that carbon fouling in the bore acts as a lubricant, that's why a clean bore shot has lower velocity due to higher friction, but what is happening to that carbon in relation to copper and other chemical deposits over 24 hours that doesn't happen in 1 or 2 hours? Maybe I'm smoking crack, but you decide whether or not this sounds plausible to you.
I think cold bore “shifts” come predominantly from people cleaning their barrel between range sessions or between zero’ing their gun. You scrub that barrel and you will absolutely have POI change for a shot or so.
You commonly hear cold bore shift discussions with fairly inexperienced shooters or casual shooters. I don’t ever hear precision shooters have issues with cold bore POI problems.
Everything starts with the shooter. If your shooting form is consistent then you go looking at equipment and other potential issues. We all must pay attention to pressure, humidity, wind, lighting, thermals, etc. At the end of the day the best rule to follow is that if you're not sure of where your shot impact will be, don't take the shot. There's nothing wrong with an ALL STOP if things are wrong. In fact, that's the safest thing to do. Great video. Thanks for all the work you and the crew (family and friends) have done to provide these videos and information for us so we can all learn.
Umm…. That last one you demonstrated is parallax, and it’s why we have adjustable objectives. The higher the magnification, or the lower the f ratio on the main objective, the more pronounced the effect. Scopes that lack an adjustable objective usually have the parallax set to 100 yards.
Unless they are top-tier rings, I line the bottom of half of my scope rings with glued-in 600 grit sand paper.
this was the exact problem i had ,missed an ibex about 9,10inches down, at 350 meters, i rechecked everything at last it was the suppressor that was lil bit loose, i thought i cant be the problem so went to the range to check , you know what happened,
The second point is really fascinating. It’s call the Law of Large numbers in stats. You’ll know when you’ve shot enough rounds to zero when the center of the groups no longer moves a significant distance. Great video!
I have zero interest in knowing the answer to this question for a big game hunting rifle. The first shot is by far the most important, and maybe up to two after that matters much less. Some rifles wander a lot after getting hot, some don’t.
@@phild9813this assumes the human doesn't overestimate their skill and has a rock solid platform.
@@phild9813 Basing your accuracy on one shot will not tell you anything about the accuracy of your first shot. If you need your first shot to be on the money, you should base it on an even larger group. You can do this while allowing your rifle to cool off. It’s about probability not luck.
Really appreciate your contribution. Smacked my forehead and…..of course. Also remembered that data should not be anally extracted !! Otherwise it’s simply so much B.S.
That must be why California makes it a felony to possess a hearing protection device. They're really looking out for us!
Seriously??? 😐
@@HookLineSinger Seriously. It's also a felony to possess a "sniper scope," which is any optic with night vision or thermal capabilities. Just think how dangerous it would be if people could correctly identify targets in low-light conditions. California law makers are truly special.
@@newscoulomb3705 makes me thankful to be in Alabama!
You mean a suppressor? Cuz a hearing protection device could be headphones 💀
@@Zer0Edits00 I said what I said. 😉
Hornady podcast #50 on group size is very interesting. Basically, you should shoot a 10-20 round group and use the center of the group as the center of your zero. and that group should be what you consider your rifle actually capable of.
10-20 shots? Maybe for Fudds. I use a 750 shot zero.
I free floated the barrel of my Ruger m77 and bedded the action in the stock because it was shooting wild. Tried all kinds of different torque on the stock screws to no avail.
Finally realized it was just a piece of wood and sanded the forend away from the barrel and bedded the action.
It really helped the rifle a lot.
The variability from shooting from a bipod vs resting on a bag is much less than it was.
Will find out next month if i drew an elk tag this year or not. Deer tag for sure.
Ive done the same with my 1995 model, Ruger m77 mark II 270. Even with handloads, about 2" inch was as good as it would do. Bedded the stock, floated the barrel, lightened the trigger to 2.2 lbs, played with different torques on the stock screws, and only got it down to 1.25" inch. My theory is, before the Ruger American, savage axis type budget rifles, that shoot deadly accurate, most rifle manufacturers didn't put a lot into accuracy. And rightfully so. Us hunters didn't either. I knew a lot of guys that 3 shots hitting a pie plate at 100, was good to go! Now that budget guns shoot 1/2 moa out the box, those higher end guns have to shoot well also. I've got a new savage 110 timberline in 243win, that with handloads shoots 3/8" all day. And a Heinz 57 AR-15 with a larue tactical 20" barrel in 223 whylde, that shoots better than any bolt gun I've ever even seen shot ! Cold bore will be 3/8" from the next 5, that are all in one hole. Like a 0.2 group. Times are good for accurate rifles.
@@Gunrunner223Have a question if ya don’t mind, So I’m wanting to put a 223 wylde barrel on mine as well, just curious, Did you keep same bolt carrier? Or did you match the barrel with a new bolt? and did you change out your buffer spring, and use a certain weight? Thanks for any info.
@@brandonbelchersr9496 you don't have to change anything. A 223 Wylde, 5.56, or 223 rem, are the same bolt face. I swapped alot of stuff, but to function, the barrel is all you have to change. I highly recommend larue tactical barrels. They have amazing reviews. And I've never seen accuracy like I'm getting. Even bulk brass fmj shoots 1.5 inch groups. Quality factory ammo, shoots 3/4 or better. Every handloads I've tried, from 50gr vmax, 52 eldm, 55 vmax, 55 blitz king, 62 sierra HP, 69 sierra match king, have all shot under 1/2" inch, and most shot 3/8" or better. Never seen anything like it. I did swap my trigger out to a timney $99 single stage 3 lb . My barrel is floated. Hope you find one you like.
@@Gunrunner223 thanks a lot, very well rundown. At least I know now I’m good on everything but my barrel, which will be a larue barrel.👌🏼 Thanks again and have good one..
@@brandonbelchersr9496 absolutely.
Hahaha lost it when you started hammering that scope
My thoughts were I wonder if Leopold warranty will cover it. 😂
The cold bore subject is really a cool one to dive into to. One thing was missed that I have run into. Action screws miss torqued make a huge difference.
A quick trick a friend of mine told me was to use nail polish around the screw heads. every time I take the gun out, I now look at the rings and the pic mounts for the nail polish to be intact, if something moves, the polish will be cracked.
I use clear nail polish to lock my screws down instead of locktite. This is a good idea though.
They are called witness marks, we did it to everything in the ARMY that could move, and affect function.
Jim’s videos amplify the correlation between more recoil/less precision. Light kickers are much easier to shoot with repeatable precision.
Cold bore shift is absolutely a real thing, Although it is not necessarily something that is present or significant enough that you will see it in every rifle. I had an Accuracy International rifle in 308 with a night force scope in the night force rings and the first shot out of this gun was consistently in the 7 o’clock position between a half and 1 inch out from the rest of the group. After that first shot, the gun would shoot a half to 5/8 minute five shot group every time. Before I sent it back to Accuracy International for warranty, I had other shooters test the Cold bore. It didn’t matter who shot the gun. It was always in the 7 o’clock position a half inch to 1 inch from the rest of the group. The factory could not figure out the problem or wouldn’t tell me what the problem was. They ended up replacing the gun with an upgraded model.
Ambient temperature and powder temp tend to cause a shift in both velocity and point of impact.
Cold bore and clean bore used to be synonymous. There is a big shift from a oiled barrel to a fouled one.
2:00 Last time at the range, I had this exact thing happen. I was shooting a new barrel and getting decent groups. Then I started noticing my point of impact shift. At first I thought it was just the barrel settling in. Then I was letting the barrel and suppressor cool down between shot strings. I reached up to feel how hot the suppressor was and noticed a tiny bit of play. I re tightened it (maybe a 1/10 of a turn) and then magically my original POI came back to the original spot. I learn this lesson first hand that day. Now I check the suppressor for snugness often
thirty years ago I had purchased a rem model seven, it shot 1 in groups when new, sent it off to have the barrel action refinished with dull finish, was very shinny bluing. the gunsmith refinished the rings and mount also. put rifle back together and it still shot good for about 2 years deer hunting, less than ten shots total and four deer in the freezer, then every thing went to crap, 3-4 inch groups. glass bed the stock, no changed, it sat in the gun safe for twenty five years. recently I pulled the old classic rifle out of the safe and did a completed relook, come to find that a tally base was loose, I knew right away that was the culprit. lock tight the bases on and the rifle now shoots just under 1 inch groups. life is good again !
Right away...25 years later😂
Whats a tally base ?
@@jayblemsin4226 Talley is a company that makes quality scope rings and bases. Highly recommend.
@@jayblemsin4226Talley makes scope rings and mounts. 😊
I couldn’t imagine shooting my rifle less than ten times in over a two year span.
For a hunting rifle I really believe in establishing a cold bore zero. What was the shot spacing on the shots. Maybe use a laser thermometer and record the barrel temp for each shot. From what I have read cold bore variation can be affected by the barrel manufacturing process and stress relieving the barrel.
There used to be a big thing where people were doing cryo treatment to barrels to relieve the stress. Never see it anymore so I guess it wasnt an issue. My little devil on shoulder tells me that what people are really seeing is cheap or poorly made barrels doing what they do. Someone like Remington or Winchester just never has time to do what a good gunsmith will do. So they have slop and runout issues galore.
Great video, I may have missed it but I didn't see anything on a fouled barrel vs clean bore, this can cause the first shot fliers.
5:32; there's a huge difference between "not tiny little groups", and having a target that looks like you were using a shotgun
Cold bore is a thing, with improperly bedded rifles, but more often is the symptom of barrel fouling. This is why I always maintain my rifles in a range of copper fouling since that will be closer to the normal state in real-world usage.
Harmonics are a real thing.
That 7oz chunk of metal whipping at the muzzle sure messed stuff up
As a hunter what i really want to know is where that first shot goes,when your satisfied you have your gun zeroed where you want it,shoot again on different days and different temps and conditions(cloudy,sunny,even rainy)if possible to make sure that first shot lands where you want it.I like letting my gun sit outside before i shoot and let it get close to outside temperature.A lot of modern powders are not very temperature sensitive but i want to know I’ve made every effort when the moment of truth presents itself.Great discussion👍
Great topic. One thing I have always done is have my action bedded and barrel floated and triggers set to the same weight.
Cold bore shift is very real, especially for rifles that aren’t free floated. Thermal expansion in the barrel changes contact with the stock, changing the point as the forces of a bullet traveling interact in new and novel ways. Now you could say “just use only rifles that are floated”, which is fair I guess. But that is a limitation in picking the tool you want for the job. Knowing your rifle, and how it reacts, is important. I’ve had rifles I’ve sold for this reason, because their use case meant that multiple shots would require a warm barrel. I’ve had others I’ve kept, because they would never be shot very warm.
No
im not so sure. i can definitely see saying once its HOT that it has shifted. But from cold to say shot 4 or 5 it hasnt had time to expand or shift. Maybe the bigger issue, as you pointed out, is not being free floated. Putting variable pressure on the barrel is gonna make it do all kinds of weird stuff. No way to actually tell if the zero is shifting due to temperature or just the stock being flexed.
@@McgSpook all depends on the rifle and cartridge how much it shifts and how quickly. But I’ve seen it happen, one rifle would consistently shoot about 4” lower after 3ish shots. And return to zero after cooling down. And if you waited 5 minutes between shots wouldn’t experience PoI shift. I could have tried bedding it for more consistent pressure, or relieving some high spots to get the contact more even, but just sold the rifle.
@@ericc3327 im sure it exist in reality to some extent. but i think people that see large shift, enough to set your zero to a different spot, have something else going on and it its not thermal related. but thats just my thinking. im as crazy as everyone else lol.
This might sound stupid but aging of the fouling in the bore can do it too. Even if that fouling is just the oil after cleaning. The carbon absorbs water, the copper oxidizes, the oil evaporates.
What we were taught through training at the S.O's office, is after cleaning the bore of the rifle run a patch through it with a little amount of oil, then run a dry patch through it. That little amount that is left almost mimics the first shot that "dirties the bore. The "cold bore" shot drastically changes the amount of shift.
I'm not sure i would trust that. No way for oil in the barrel to evenly dispersed or take the place of copper. Even after a good cleaning my last step is alcohol patches to remove every bit of solvent and cleaner that may have been left behind. Even a foul bore is still shifting until its gets enough rounds down it to lay in some copper. I wont trust it to stay stable until at least 5-10 rounds. Personally believe what most people think of as cold bore is kinda what you are explaining. The temperature of the bore means very little, the condition of the rifling means a lot. A "cold" bore that is fouled should not drastically change anything. ymmv
Your brave. Baffle strikes occur when your suppressor is loose.
Very informative Jim ! Thank You .. Just read ottokite post and reminded me of a drifting zero on a GA Precision 300 WSM and couldn't figure the culprit until I took the scope off and one of my Premium rings had a hairline stress crack .. Called the company and he told me they had some metallurgy issues with a batch of rings and I returned the ring to them and they sent me a new one ... Back in business ... Hasn't moved again...
Thank you for sharing all your wisdom I as a new hunter I like to learn from people like you who have experience and you explain well thank you I didn’t know there was a difference being a little lost that’s why it didn’t hit them
Hey Jim,
When culling deer, after 2-3 shots we check the mod. Although, it happens you drop 4-8 in one salvo but try to not rush and if possible to keep in mind the heat is building and mod could shift.
I am lucky in that my mod never moves when culling.
You must use a heat shield/cover on your moderator, or you might regret grabbing it after 4-8 rapid shots.😮🔥
@@williamgaines9784 it's just wrapped in nice camo tape. It really doesn't happen often. The spigot mods seem worse for it
Enjoying the content of your videos from over the pond in the Uk.👍
I have a Ruger M77 Mark II .30-06 and I have only had to re-zero my scope on this rifle once in 30 years of hunting. And I have hunted with it every year for 30 years. I even have a fairly cheap scope on it. It is a Bushnell Trophy 3-9X40mm. The reason I had to re-zero is because I lost a screw gromet my sling and the rifle fell off my shoulder and the end of the barrel hit the gravel road!! OUCH!!
May I suggest locating your rifle in the hard case with the scope closest to the handle. The rifle will then take the weight as you carry it and when you set it down.
Very good information. I really enjoy your videos and your honest, unbiased opinion on equipment. I agree with you about the "Cold Bore Shift" phenomenon.
It’s mostly shooter input that makes groups open or zeros to appear to wander on a great rifle. Also atmospheric pressure, wind, temperature and humidity will affect the zero. Ammo is also not perfect. It is impossible for a human to put the exact amount of pressure on the cheek weld, same pressure on your shoulder, or your grip, much less trigger pressure. You can have a 1 lb trigger and crack it at 1 lb or 4 lbs. Then as he said your eye can be a touch off of center up, down, left or right. Most people don’t shoot nearly enough of conscientious practice to be remotely good enough to wring out a great rifle’s accuracy.
That Winchester really did not like getting heated up.
I have a very accurate .22. I too have observed this group shift in impact due to position change.
Some good stuff again. Now I have check my guns again. Just when I thought I had all my guns dialed in. Good job Jim makes very good sense. CW
I remember Johnny’s Reloading bench had a little fan gadget that you put into the chamber and blow air down the bore to speed up cooling the barrel back to “cold” bore status. That helped him speed up the process when trying to fine tune his hand loads.
Check mounts and trigger pressure too high, pulling some shots. I zeroed my Savage model 12 with custom heavy barrel and many mods to 1/2 inch five group, then drove 3 hours to a deer hunt. The mounts (rings) fitted by the gunsmith moved by the time we got there. When i got home, i found he had not bedded the pic rail and didn't torque the mounts. I use a case too! Cold bore is bullshit. I've been an f class shooter for years and its best warm with heavy barrel. Cold bore only affects thin barrels. Biggest issue people forget is custom trigger, trigger weight (1.11-1.15) and plenty of dry fire practice.
I agree with everything you said , however your zero is only great if when you shoot after zeroing the external variables / day time conditions are identical from whe you zeroed the rifle . I always zero then go hunting . Bullet impact is different even with season or temperature change .
Cold Bore is 100% real.... BUTTTT not what most people think anymore. It was a huge and very real problem for hunting rifles and pencil profile barrels in the 60's and 70's. By the 80's the cold bore shrunk down to less than 2" shift after X number of shots. Thats the second bit of it. Cold Bore refers to the first set of shots before the stresses in the steel change the harmonics and muzzle point to their warm state. On my Marine Corps Issued M16 I knew I had about 15 rounds of rapid fire before it started pulling a little right (2009 manufacture FN upper). This however was less of a pull than the accuracy from round to round.
Modern stress relieving of barrels cause less than an moa of shift from cold to warm state and good barrels don't even have that much. When measuring out a batch of match grade sub moa barrels a few years ago I measured the mechanical cold bore (shooter removed, locked in vice, scope set with vibration damping glue, etc) at about 1.5 cm at 100 yards. Most short action had a thermal shot capacity of about 5 rounds and intermediate cartridges had about 10+.
It only really matters when hunting vs rapid fire, life or death vs plinking.
love your channel, canadian subsciber. im 55m, a gun nut, as far as canada goes. i have a 7 mm rem mag. i customized in 1990ish.
i ts a remington 700 bdl., 7mm rem mag. i traded out wood stock for a fiberglass/ plastic stock. idk. took off the front sights, didnt like the screw holes, so cut off two inches. had it recrowned, trigger and bolt work done. also nickel plated it.
so i lost 100' fps per inch , turning it into a 280, but shot reloads, getting back my velocity. also i glass bedded the action mysrelf, when i was 20ish. reloaded fire formed 160 nosler partitions and put 3 shots in a quarter off a tailgate with minimul support, probably a rolled up coat. maybe its the shooter. dont understand why your challenge was so hard. all id need to do would be adjust my zero from 1" high to zero high.
anyways .....love your channel
I always wonder as a white tail hunter isn't the first cold bore shot the most important as usually the first shot after hitting your stand is the most important
I'm a mechanical engineer, so I overanalyze physics. When I watch shooting videos, it's obvious that the shoulder contact to the stock is below the center of the barrel, so there must be a tendancy to lift the end of the barrel. If I designed a rifle, I'd raise the stock, and therefore the scope so the recoil doesn't affect the aim. That would also put the scope closer to following the bullet drop (assuming you added a tiny shim under the bottom ring). I think when I was a kid (Leopold? Redfield?) made a scope mount that would let you look below the scope to use the iron sights for close shots. Might even allow adding a mini-Red Dot under the scope. Thoughts?
People may be confusing clean bore vs cold bore. I have had many different rifles and especially mussel loaders that shoot horrible when they are clean. So maybe what some would consider a fouling shot is being blamed on cold bore
I generally agree with cold bore being cold shooter. Also, zeros shifting due to variability in shooting technique is pretty frequent as well. If guns have a “cold bore” shot, I usually just assume it is a bad barrel. Not worth messing with and swap it.
I would very much like to see a distribution graph of the 5 days worth of shooters group size and zero error. Seems like everyone thinks they are 1 MOA all day long shooters, but judging by the video most people are 4 MOA all day shooters with a 3" zero error.
As for the cold bore shot, Erik Cortina and Speedy were talking on a podcast. I think it was Cortina that said he sent a puff of graphite spray down the barrel after cleaning and it resulted in his first shot grouping with the rest a.k.a no cold bore POI change. If this is repeatable, perhaps it's really CLEAN bore shift.
Your group sizes will likely tighten up or spread out with inconsistent suppressor tightness. Just like using a barrel tuner.
please do a segment on why/how the direction of the light source changes POI. It makes o sense to me.
With open sights I can see how light direction shifts the apparent zero, but not with a scope.
I had an issue one time with altitude change. I was zeroed at 6000’ and traveled for a hunt and was at 2600. I normally hunt above 9000. So my scope wasn’t off a little it was way off. After that I learned that if you travel for a hunt you have to hit the range when you get there.
Great content as always. I do have a comment on the cold bore discussion. My favorite hunting rifle shoots the cold bore shot 3/4in high and 1/4in right every time. I have shot 1/2moa 5 shot groups by cooling the rifle in-between shots with a barrel fan. Once the rifle is warmed up the group stays tight until round 15ish and then things open up again. I always sight my hunting rifle to "cold bore" zero...... I think it comes back to every rifle having its own little nuances and the only way to be prepared is to put rounds down range. Practice makes perfect!
You're trying to mix hunting where cold bore groups only matter and shooting for groups. That is a fail there.
Facts!
I wouldn’t necessarily say the zero is off if it’s on when things are secure but off when things are improperly fastened, however this information is valuable, don’t go shooting with a loose muzzle device
I have a hard time believing a properly mounted scope on good rings that holds a zero with the tremendous shock loading of firing a round, especially repeatedly is going to lose a zero from vibration and bumps in a vehicle ride, or even less so while riding on a backpack. You could make an argument that if it's not in line with the recoil it won't resist bumping as much, but if it's rigidly mounted, it's rigidly mounted.
Especially if it's in a case in a vehicle, it'll bounce in the case but nothing is going be able to wack the scope out of alignment relative to the rifle.
Other than that, great video. Never thought about sighting in relative to the sun, that explains the change in accuracy between certain shooting sessions while still maintaining great precision.
So I just bought a new boydstock last year to put on my Thompson center venture 7mm 08 and there was so much play in the barrel lug area that you definitely had to glass bed it! Even though I was getting good groups still in the glass better too much play too much play in the holes for the auction screws, so I finally got that done now as of today, May 10th or whatever it is. Mother's Day 2024 and this week at some point I will get it out and recite it in, and I'll go from there which I went to a different load for that gun. Also with Barnes ttsx bullets 140 grain. I put a new scope on it last year which is the Leupold 3 to 15x44 Leopold brings and bases and, I cleaned all the copper out with copper solvent. Which I was getting 3/4 in and then 1/2-in groups but I thought I could do better with that bullet and with the new powder I was using CFE 223.
If you're leaving your gun barrel exposed to the sun it WILL heat up. That steel will absorb a bunch of heat from the sun EVEN on a cool day. Keep the rifle in the shade always. I've been out on a 50 degree day with zero wind and set my rifle out in the sun. In no time the barrel is VERY hot from the sun shining on it directly. You zeroed your rifle in direct sunlight in the middle of the day without shade, but then you take that shot of a lifetime and miss because you're hunting at first light or at sunset while it's still legal to shoot.
These are all basic fundamentals of scope mounting correctly. Even parallax will influence your zero if it’s off.
My hypothesis on so-called cold bore zero shift (which I also think is a myth, at least based on personal experience) is that it has more to do with first shot/s after having cleaned the rifle, maybe still very slightly oily in the barrel and perhaps bullet moves ever so slightly faster through the barrel that first time. I've never really experienced that my cold bore shot is significantly different from the rest of the group, and if it was the case, it would be a bit worrying on a hunt, where your kill shot is basically always a cold bore shot...
Another thing that I have found that will affect zero is not lapping in your scope rings. I have tried this before and it does help. I had a gun that would move zero. This is about 10 years ago when I really started getting into guns and accuracy. I was researching and came across people saying to lap in your rings. So I got the stuff to do it and it worked, never had a problem with the zero after that. Yes it was the same rings and scope that I was having issues with before. From then on every scope I mount I lap the rings in.
i think that just means you had bad rings. For example, people like NF will void your warranty for doing such a thing. I will say that modern mfg is capable of a lot better product then 20 years ago. In short, buy good rings and your days of lapping rings will be over.
Yes good rings do help. But it is all a tolerance stack up between the rings the mount/rail and the receiver screw holes. All three have a tolerance that can turn the rings out of parallel with each other. So when you are lapping the ring you are essentially straightening the I'd of the ring to the mount and receiver to make it all parallel to each other. Especially the Remington 700 two piece mounts will be off by a little. The last one I did I put Zeiss rings on a premium ar upper and they were still off by a little bit. They were turned one way or the other and not directly in line with each other. Nothing can be machined to 100% perfect unless it is all matched and hand fitted to that one gun. But I will stick with lapping them it makes me feel better that I did everything in my power to mount it good and solid. So I don't have any excuse other than I missed the shot and it wasn't because of my equipment.
Stop buying $25 rings.
People mistake cold bore for clean bore. Cold bore has no noticeable effect on any of the hundreds of rifles I have shot. But if you have cleaned, even just a dry patch down the bore. Your first shot (and maybe 5-20 shots after with a full copper remediation) will be a flyer.
I've seen several guns that will throw a first shot well off the mark. Most of them have been lever actions.
I would not have one The bang is better to hear
Shoter position is crucial in point of impact. In 100-200yds hunting situation is irelevant. BUT on long range or high stakes.....like Olympic shooting is HUGE..... alot of drills and exercises are focusing on repeatability of postion
Whatever the true cause is, I suggest to test for zero the same day before the hunt. Ammo temperature is also a factor. Hunting early or at noon or late... afternoon. How about testing offset keeping hunting rounds in a vacuum Tremo flask for more consistent temperature control.
every savage rifle i have bought new has a ton of oil under the mounting rail. after zeroing, it would shft. removed the rail, cleaned and dried the rail and action, then mount again with loctite.
the 338LM 110 even had mounting rail holes that went through to the action into the bolt area. any cleaning fluid used would wick into the hole and loosen the loctite. had to be diligent.
Not sure if it applies to centerfire but if i remember right there was a couple people that proved the "cold bore" shift in 22lr was moisture related. They could do a breath of air through a straw into the chamber and down the barrel and the shift was gone. I think Josh on pursuit of accuracy had a video on it. I think some of the center fire shift is cold shooter and positioning of youre face and eye behind the scope
Cold bore shift - some have said that this is due to residual moisture in the barrel. I have no way to confirm this, but I have noticed a difference myself. But, as you said, it may be that I am all wet on the first shot.
None of my hunting rifles that were glass bedded had problems with zero shift. The Howa .223 i use would was very fussy with different ammo and would shift at different temperatures. A full action bedding job and now it is far more consistent, even though group size hasn't changed.
In my experience, there IS a different in bullet impact between a cold barrel and a hot barrel, but unless you’re using the same rifle for hunting and competition, most people won’t be able to tell a difference out to about 300 yards (give or take depending on the caliber, MV, bullet weight, etc.). I don’t shoot competitively now, but in the past I’ve always used the cold bore method of zeroing for my hunting rifles and shooting various amounts of rounds at a time for competition rifles. Of course, barrel weight and thickness, action type, and action quality all have an effect on this.
In conclusion (as with most things shooting), how much a cold bore vs hot bore zero varies greatly depends on a multitude of factors and there really isn’t one right answer.
Thinking about cold bore. I’m just an average everyday shooter. I work in a machine shop. I could see a rifle bore changing with temperature. Variables might be material of barrel, thickness of barrel, tempering of barrel, consistency of atmosphere during machining causing a less accurate barrel. Maybe the bore isn’t directly down the center all the way; ie; barrel thickness varies around diameter, the rifling is inconsistent down the barrel. I’m not a gunsmith or anything. Not even a machinist. I just work manufacturing machined parts, some thick some very thin. Some of our parts have 2000 lasered holes .025-.030 diameter. The part changes.
I've experienced a POI change between the first shot and subsequent shots and was able to correct this shift by remounting the scope or bedding the stock. I've not seen where this shift cannot be corrected. There is a real and measurable difference in velocity, not POI at 100 yards, between the first clean bore shot and subsequent dirty bore shots with some rifles.
I remember reading a long time ago that you could eliminate "cold bore" shift by breathing into the barrel before the initial shot. If I recall it has to do with the level of moisture in the barrel. I have tried it with my rifle, and it worked for me. Get a straw, and shoot a puff of air or 2 down the barrel prior to first shot and see what happens compared to when you dont.
Accuracy is all about consistency. If things are not consistent from one shot to the next, things will change.
Jim, you definitely get a 👍. Good video.
In my opinion, using a hard case, people usually put the gun in upside down. When they pick the case up by the handle, the gun is carried upside down. The weight of the gun is weighing down on the scope. I dont know if that could change impact or not.
Cold bore shift is real. A primary cause comes down to how the barrel is made. As steel is being forged and shaped, it can build up internal stresses where different grain patches in the steel want to naturally flex some direction. If the steel isn't properly stress relieved, the barrel will bend itself one way or another when it heats up. The hotter and thinner the barrel, the easier it is for the internal stresses to flex it. The stories of early M16s shifting zero as they heated up are at least partly true because metallurgical processes have advanced greatly in the last 60 years.
A barrel that was properly stress relieved during manufacturing should have minimal shift as it heats up, if any at all. But it's also important to remember that your groups will always open up as the barrel gets hot. Lightweight hunting rifles, those with thin sporter barrels, can start opening up after only a couple shots. I had a Creedmoor that could place the first two shots relatively close, but couldn't hold better than a 3" group if you fired more than three rounds in five minutes. So it's possible what one person thinks is cold bore shift is really just the barrel quickly getting hot and the opening up.
You could have mentioned mirage, either environment or heat from the barrel. I think it affects people more often than shooting position.
I would say ammo if you're using ANY factory ammo. The light thing I definitely agree with, experienced it myself. Cold bore for me depended on how I cleaned my barrel. My cold bore shots are spot on now. BTW, I'm shooting a gas gun in 600yd F-TR and do pretty well with it.
Good job, you covered many potential causes of zero shift. Might want to address mirage causing the image that you see to shift. Usually 1/2-1 moa.
Good info, makes you realize once you found the right ammo and zero it, there are still things to keep track of👍
If this is factory loaded ammunition, I could see groups that large. I always work up a load for my guns and continue with the best for each gun.
Depends how you define zeroed
Cold bore that’s more than 1/2 moa is barrel that’s not made right, had a bergara HMR that they warranties and replaced the barrel for me. It was shifting 6 inches from cold bore over a 4-5 rd shot string
Warne rings are rock solid, usa made and affordable.
I always check my zero with at minimum 3 shot group the day before I hunt. Period. Some rifles will have a sizable difference with a cold bore shot. So If that's the case, go out and take one shot. Wait 30 min, take another, then wait another 30 min, and take another. Then center your reticle in the middle of the group. Remove the worry and hoping... If you're traveling, or flying to a hunt, it's going to be different due to elevation, temp, and humidity changes so zero it at hunting camp. Just check it and then you can relax about that.
Regarding cold bore shots, I have a hypothesis in its infancy that I really want to test more. I picked up a garmin chronograph and decided to just chrono everything my buddies and I shoot, along with some other guns we get to use through our job (Bergara b14 and hmr in 6.5 cm, seekins hit 6.5 cm, dmr 556, and sp10 in 308, Marlin trapper 45-70, Christensen ranger 22 lr so far). I noticed the velocity of the first recorded shot was generally one of the closest to the average over 10-20 shots. I want to test this much more before I put any stock into this but perhaps taking a lot of time between shots to allow the rifle to cool would improve zeroing. This would mainly apply to hunting scenarios where having the best zero cold bore is essential, but also developing a dope chart closest to that cold bore shot’s velocity and average velocity would be extremely helpful. But in reality, most people don’t shoot well enough for it to matter, whether it’s abilty to adjust for elevation/wind, ability to create and use a stable position, rifle/optic quality and gear setup, or what I just like to chalk up to fudd lore.
Any time weather or elevations change your zero changes
My muzzle break went loose on me at my NRL comp, I started missing and did a check on my gun and realized my break was all loosy goosy. Tightened it up and was back on.
@backfire Jim, Great channel!! Great advice!!! My gun strings hard after the third shot so that's where's its zeroed. Its a pencil barrel so you have to wait what seems like all day for it to cool all the way. Ive been going through this gun as it had issues which you stated in this video which were affecting the zero along with my shooting it hot. I'll double check three cold shots next time i shoot it as its a hunting rifle and i doubt i will get more than two or even three shots at anything.
Man you're brave. I'd be terrified of a baffle strike doing that.
To touch on some points further. I typically shoot multiple 3 shot groups. I give the gun 10 minutes between 3 shot groups to cool off and find that works best for me. I still end up using the data of around 10-15 rounds to determine where the zero is.
Also instead of aiming for a perfect bullseye, I typically aim at the base of a diamond target. Gives a much tighter aiming point than a large open orange section of a target.
What did I learn today? Don’t buy Winchester
I mean :P, you have a point 😅
Thanks for the information regarding light changing the zero