Tight Tolerance Chambers: Best to Worst
HTML-код
- Опубликовано: 7 окт 2024
- In this video I discuss Cartridge chamber dimensions and specifically freebore diameter. I discuss the importance of having tighter tolerances with your freebore diameter. I also show a list of popular cartridges and the measurements. Hope you enjoy the video!
A couple of corrections I would make...some of the cartridges you say have the worst freebore tolerances (like the .243) actually don't have any freebore at all. That dimension of .2463" is just an arbitrary point where the 45 degree taper ends and the 1.5 degree lead/throat begins. So it's a bit unfair to compare a design with zero freebore to a design with a sigificant amount of cylindrical or "parallel" freebore. Second, bullet diameters are not exact as you imply. For example a .264" bullet is not exactly .2640", but has it's own tolerances in manufacturing. The majority of rifle bullet specs I've looked at have a tolerance of plus zero, minus 0.003". So that bullet could be as small as .261" and be within factory specs. Most bullets today will be much closer to the stated diameter than 0.003" but they still vary a bit. Having said that I still think this is a very relevant topic to discuss. Traditional tolerances are +0.002" on the chamber and -0.008" on the cartridge. Add that to about 0.002" of difference between chamber max and cartridge min dimensions...you could have up to 0.012" of difference between your cartridge and chamber. That's enough that you could wrap a piece of masking tape around your ammo and still chamber it (don't actually try that, it's just for the sake of explanation). Higher quality rifles tend to be closer to that chamber minimum dimension (including Weatherbys).
By factoring only the diameter of the freebore and not taking into account how long (depth) the parallel freebore is cut and where the lead angle starts you are missing quite a bit of important information. Case in point, the 300 Win Mag has zero freebore, so at the case mouth the chamber is cut to .315 which immediately starts into the 1.5 degree lead and in only roughly 300. depth is down to a bore size of .300. Even a 110 grain. 30 caliber bullet with a short bearing area will be fully supported by the case neck and rifling at the same time as it is funneled into the rifling. The 300 Weatherby on the other hand, has a parallel freebore of .3084 that is nearly .350 in length before it starts its lead angle. Which is long enough that a really short bearing area bullet may not receive full support as it transitions into the rifling. This holds true for the .243 Win and .264 Win Mag also.
Good observation. Suddenly someone publishes a video of certain rifle chambered in .300 win mag, and it happens to ba a flaw in a 50-year old design.. so maybe we need to rebarel our rifles for a faster twist PRC cartridge..
Awesome video. Thx for taking the time to collect all the data. Below are the values of the best and worst per caliber in percent.
22-250: 0.2%
22 Swift: 0.9%
6mm ARC: 0.2%
243 Win: 1.35%
257 WBY: 0.2%
25 WSSM: 1.6%
6.5 CM: 0.2%
.264 Win Mag: 1.5%
270 WBY: 0.1%
270 Win: 0.5%
7mm WBY: 0.1%
284 Win: 2.1%
300 WBY: 0.1%
30-06: 0.8%
300 Win Mag: 2.3%
This is not tolerances but specifications. Tolerances would be if the specification says it can be fall within x-y measurement. It does make good sense that the Weatherby's would be tighter with the longer freebore dimensions.
Correct. Typically the tolerance in freebore diameter is +.002. So arguing about .2845 vs .2846 diameter is a moot point. Get a good quality chamber made with a great quality reamer.
All of my 300 win mags are very very accurate. Not sure how much i buy into as much of this. Ive seen a couple very innaccurate prc rifles. How can one ever tell what makes a rifle innaccurate. Tolerances vs barrel vs 10 other variables. Mental masturbation. A rifle shoots or it doesnt. If it doesnt theres some things to do that may fix the problem but if not it likely the problem is what cartridge the rifle is chambered in
I agree! A lot more to it than just freebore tolerances
Excellent video and extremely informative. I would have never guessed there was that there was such a large variance, from one cartridge to another in the same bore diameter? Thank you for posting!
Glad you enjoyed it!
That makes perfect sense why weatherby rifles are able to achieve their accuracy with the large amount of free bore they have because they are all making big jumps to the lands
Not every rifle manufacturer out their cuts an exact Saami spec chamber depending on rifle manufacturer and what you're paying for a rifle those tolerances may be tightened up with more of a match-grade chamber
Very good information. You did alot of work on this video. Appreciate it!
Some good info and a good video on the 300 win mag and other’s and yes it would be best to roll your own
The problem with SAAMI is that is SAAMI data and most independent chamber reamers makers (PTG, Manson, Climber, etc) have already solved this problem on their end. My .30 caliber chamber reamers all measure .3085”, in fact all my chamber reamers measure exactly .0005” over the bore diameter in the free bore or throat area. I use PTG chamber reamers almost exclusively.
Many of the Winchester cartridges you mention do not have a freebore section. They just have a single taper with no freebore section to align the bullet shank. Winchester followed this design up through the early 2000's with the WSM series (with the exemption of the 308, which more closely resembles the 7.62x51).
Free bore is the distance from the neck of the case to where the rifling starts. You are talking about the diameter of the neck of the chamber or neck tolerance. Weatherby is known for having the most free bore of any rifle manufacturer.
I know you think I'm making it up... even though I showed you the drawings from SAMMI.... just go Google it
Most hunting cartridges do have more tolerance built in, that is a lot of the difference say between the 300PRC which is basically a match chamber and the 300 Win Mag which has loose tolerances compared to it.
But no I do not think you are making anything up!
When talking about Weatherby having the most free bore of any rifle manufacturer keep in mind they have the longest free bore. But not the largest diameter of free bore. I believe when discussing free bore it is important to keep two dimensions in mind. The length of free bore and the diameter of the free bore.
Tight tolerances aren't great when your 280AI chamber is so tight Nosler factory ammo will barely allow the bolt to close. Off to the barrel maker it goes. 😢
That sucks
That was some good info and some sensible conclusions. In my mind the 300WM being so long and headspacing of of the belt (in factory ammo) means that any inaccuracy in the barrel where the belt rests, or any burrs or dirt, will cant the entire cartridge and throw off accuracy.
I own a savage 110 storm in 300win mag and iv had good luck with a few different factory loads. Especially with Sako 180 game heads. So I don’t know much about free bore but whatever the savage has is working for me lol! Good video ! Cheers from Canada eh 🍻🇨🇦👍🏻
Nice!
🕵️♂️ I also wanted to mention that I tested bullet penetration at 300 yards with the 270 Winchester Shooting the 150 Grain Nosler ABLR bullet! Unfortunately, I didn't bring enough 1 Gallon Milk Jugs! ☹ I hit it dead center and the bullet penetrated through All 5 Water Jugs - with no veering off course - and kept going! 😳 I think that it is safe to say that it will do a more than "Satisfactory Job" on Game Animals! 😯
One of your best videos. Very interesting and informative.
Thank you!
Eric cortina had a guest awhile back saying weatherby mag calibers had pressure issues and had to open up free bore diameter to keep guns from blowing up. Not sure which calibers he was talking about. But I was surprised.
I watched it. The guest was explaining why Roy Weatherby put so much freebore into his rifles. It was to lower the pressures and get higher velocities.
Just so you know I am a 60+ year gun collector and reload and hunt as well. The most accurate factory rifle I have ever seen was a Browning in 300 WM! It was a little picky with factory ammo but shot 1/4” inch with some factory ammo so I think you are sweeting the little things too much for hunting and should do more shooting practice when the biggest mistakes are made when shooting!
Nice! Thanks for sharing
I only have 1 300 win mag, its a savage 110 stealth evolution but it shoots lights out with everything from cheap ppu softpoints to 225 eldms. Small sample size but its an awesome gun.
Nice!
🕵️♂️ A Perfect Opportunity to Discuss This! Yesterday I Took Out My 270 Winchester And Shot It, Starting at 100 yards! My 5 Shot Group Was Well Within Easily Being Covered With A Dime and additional space around "the hole" (a less than 0.5" Group)! However, the "Flyer" of the Group - that kept me from a "True One Hole Group" (looking like only 1 bullet was shot into the target) was actually a chambered round that was actually hard to close the bolt on (Because the Bullet Was Actually Seated Out and Closer To The Lands), but I wanted to see what would happen more than I wanted a "True" 1 hole group (So, I Rechambered the Cartridge and Shot It Anyway?)! Now, usually a bullet closer to the lands will give you better accuracy, but not in this instance! 🕵️♂️ WHY? I then shot my friend's 30-06 (a 3 shot group, because he brought limited Ammunition, and shot a "1 hole" less than 1/4" group with a rifle that doesn't usually shoot nearly as accurate as mine and at the right height above the bulls eye at 100 yards)! I then move out to 300 yards and, with my rifle, shot a "5 Shot Group" at between a 1 1/4" and 1 1/2"! As Eric Cortina Says, "The Target Doesn't Lie"! 👨⚖ The 300 WM has Won Camp Perry and used to hold "The World Record" for 1000 yard Accuracy! 🕵️♂️ WHY? Having Worked In Manufacturing, I Can Tell You That Unlike Many US Companies, Most Foreign Companies Operate Under "Six Sigma Production Principles" and That Their "Manufacturing Tolerances" are 3 Orders Of Magnitude Better (out to the sixth digit behind the decimal) Than Most US Companies! But, You Have 2 Major Components Here: The Rifle (Chamber and Barrel) and the Loaded Ammunition (which I contend is the "Bigger Variable" here)! Thus, Variations Will Always Exist and Not To The Same Degree By Every Individual Manufacturer and Every Individual Product Themselves! My Target Says, "Dead Deer" and that is what matters to me! 😂 WHAT REALLY MATTERS THE MOST HERE - OF ANY OF THE "VARIABLES" - IS ALWAYS THE MAN BEHIND THE TRIGGER AND WHY MY FRIEND LET ME SIGHT IN HIS RIFLE FOR HIM (BECAUSE HE "UNDERSTANDS THIS" FROM EXPERIENCE 😜)! 🎯
Correct
🕵️♂️ So, If We Look At The Variables (And Their Are Many), Besides The Individual Shooting The Rifle, Is It Really The Chamber Dimensions That Should Be Our Biggest Concern For Accuracy? 🤔 I Watch a Video Just Yesterday on Horneday's Superformance Factory Ammunition - Where The Velocity Variations of Their 270 Superformance Ammunition Was 150 ft/s Apart Between Shots! 😱 Now Horneday, WHO MANUFACTURES AMMUNITION AND NOT RIFLES (Like Nosler Does), Would Like To Have You Believe That Their Cartridge Designs Are The Best (Because Their Cartridges Have The Tightest Chamber Design Tolerances)! 😂 However, Your Own Presentation Showed That Their Claim Just Isn't True - By Your Comparing The 7mm Remington Magnum To The 7mm PRC! 🤥 So, Would 1 Ten Thousandths Of An Inch Difference (0.0001" - or even 0.001") In Tolerance Between The Two Cartridges Matter More For Accuracy Than A 150 ft/s Ammunition Velocity Difference Between Shots For Accuracy? 🙄 Horneday's Marketing Team Would Love You to "Buy That Tolarence Claim", But They NEED To Focus On Making MORE CONSISTENT AMMUNITION, Instead, If They Want To Keep My Business! ☹ WHY? Because I Know Better! 👨🎓 THE TARGET DOESN'T LIE, BUT THESE MANUFACTURING COMPANIES DO!!! 😜
🕵️♂️ So, Looking at Horneday's Own Information and Using Horneday's Own Ballistics Calculator - What does that 150 ft/s velocity variations (with the 145 grain ELD-X Superformance Load - Listed Box Velocity of 2,970 ft/s) result into regarding Drop and Drift variations at 500 yards? It would be a 4.3" difference in bullet drop and a 0.9" difference in drift at 500 yards! That could be the difference between a kill shot and a wounded animal, depending upon where you aim and the angle of your shot! Additionally, while the "Reviewer" didn't have a problem with the 270 load, he previously did a video on the 6.5 Creedmore, where the ELD-X Bullets were Completely Fragmenting Apart! 😱 THESE "INCONSISTENCIES" ARE NOT GOOD HORNEDAY! ☹ Horneday, I would suggest focusing on a better bullet design and powder charge consistencies and forget about "Touting" your cartridge designs! 👨⚖
🕵️♂️ The Reviewer Was MASON LEATHER! Earlier in the week, he did a video on the 270 Winchester's 130 grain Horneday CX Outfitter Load - In Which He Called Them "WILDLY INACCURATE" and was getting 7" groups! 😱 CASE CLOSED! 👨⚖
Just for this discussion; This quote may explain why the longer freebore."300 Winchester Magnum is a magnum cartridge designed to fit in a standard rifle action." It is based on the .375 H&H Magnum, which has been blown out and shortened where as most "308 -.338 magnums require a "Magnum action." Also the bullet manufacturer's tested and recommended bullet seating depth can differ because of their bullet weights, ogive shapes and metallurgy, the latter needing to be seated longer in a calibers chamber and be within SAAMI specs for all same cartridge chambered rifles. I suspect Winchester purposely created more distance to lands to prevent potential Bullet Jam and therefore dangerous chamber pressures already inherent from increased case powder capacity over standard cartridges. Weatherby magnum chambers and cartridges are well known to have higher chamber/case pressure tolerances.
I've heard discussions about how the transition between free bore and rifling is handled is potentially as important as the diameter difference, the more sloped the taper into the rifling the better being thought to better
I'm sure it does! Thanks for commenting
You do realize that the differences of .001” of freebore between some of these cartridges is negligible. A piece of paper ranges from .003-.005” I think freebore contributing to accuracy is negligible. I was surprised to see how much freebore the .300 Win Mag has also. But I’ve seen some very accurate .300 WM also… Same with .308 and .30-06. 🤷🏽♂️
I agree 100%. If I'm struggling to get a rifle to shoot accurate I'm never ever going to say it's a free bore issue and give up.
To be fair I've had issues with bergara in 300 PRC also and one in 243 win accuracy was horrible and stepson had one in 6.5 creedmore bergara fixed them both but for what they cost they should have not happened at all
Thanks for sharing. Really could be Bergara.
Tolerance on freebore diameter's are typically +.002". While the specifications may vary, they rarely vary by over .002". Get a good chamber with a high quality reamer.
One thing to keep in mind, and one reason I will always choose the win mag over the Weatherby, is that if you're reloading you can use the Sinclair bump gauges and only bump the shoulder back 1-2 thousandth. Simply not possible to do that with the Weatherby because of the shoulder. Your brass will 100% last longer with the win mag.
I have no trouble measuring my 338-378 brass for proper shoulder bump. I use a dial caliper and the appropriate size of powder bushing from my shotshell reloader. It works great.
@@10-4CodyWade it will never be as precise due to the double radius shoulder. You can basically make any .300 win mag headspace off the shoulder, it's very hard to achieve that, if it's even possible, with any Weatherby mag.
@@coltinallenscott How precise does it need to be? You're saying 1-2 thousandths is what you use on the Win Mag, and that is easily achievable on the Weatherby with a dial caliper. Not sure why you'd need to be any more precise than +/- .001 on a shoulder bump. You're not even taking an actual measurement, you're just comparing a fired case to a resized one. If I was having any trouble taking measurements I could easily crank out a bushing on the lathe to match the shoulder radius. It's just not needed though. I have a 300 Win mag and the 338-378. Both are set up to headspace off the shoulder.
You're pretty much right on there R. Dubb. I give you credit for sticking your neck out there for all the RUclips gun, cartridge, caliber and ballistics "experts" to take a whack at it. 😂
Thanks for watching. I'm going to make some 300 Win mag owners angry
@@ReloadingWeatherby
Have at it man! 👍🏿
this might help to explain why my particular 30 06 has some accuracy issue with lighter bullets, but seems to do better as you increase bullet weight with the gun. not saying that is the only reason but may be a contributing factor.
Years ago we tried 125 noslers in my custom 06 my grandfather gave me. It would hardly keep bullets on the box we used for the sight in paper to be on. Some even canted sideways when they hit. Needless to say, we went back to the 165 interlock shooting 3/4 inch group and never looked back.
@@rosshill2565 the gun i have is a marlin xl7. Literally have tried numerous bullet powder combos. It will shoot 165 ballistic tip okay. But ive never gotten sub moa with the gun
Is that a CCI BR#2 primer in your 300 Winchester Magnum case at timestamp 10:15 ?
Yes
I’m stoked to have finally found some 180 grain accubonds to try in my 30-06. Have you loaded those in 06 and if so any tips on making them shoot in an 06?
I haven't tried them in 30-06. 180 gr Accubond have been picky in my 300 Weatherby. It prefers the 200 gr Accubond
@@ReloadingWeatherby Are they picky about seating depth? Hoping they will work out in my 06.
@NCWoodlandRoamer I believe they are. My friends 30-06 loves the 165 gr Accubond. Gets under half MOA with it.
What does this mean for how manufacturers actually make chambers? Does Bergara follow saami and others go a bit tighter? Will there be chamber pressure issues with certain factory ammunition if certain manufacturers make tighter chambers?
All manufactures will attempt to make it at SAAMI spec. But we all know that they mess up.
🕵️♂️ I Noticed That the 280 AI Wasn't Listed? Does the Newer SAAMI 280 AI Have Tighter Chamber Tolerances Than the Pre-SAAMI (Ackley) One? If So, What is the Actual Measured Difference? 🤔
I forgot to add it. It's not good.. but not terrible either.
🕵️♂️ Do you know which was the tighter of the two (Ackley or Nosler/SAAMI) and what the values were? 🤷♂️
You have 22 nosler in the 24 caliber section
Yeah... I meant 24 Nosler
🕵️♂️ Does Weatherby Have The 0.0004" Chamber Tolerances in ALL of Their Rifles, or Just Ones Chambered in Weatherby Cartridges? 🤷♂️
Not sure
Yeah but don’t world champion long range shooters use .284 win which is at the bottom?
You can't get a 284 Win in a factory rifle. They are all custom built, with custom chambers.
Just because u have the sammi specs for the chamber there is no guarantee that factory rifles will chamber that rifle in that exact sammi spec i have 50 custom built rifles and iv takn aprt alot of factory rifles and there chambers are all slopy thats why some factory rifles are shooters and some arnt
Yep
The 22 Nosler is not a 6mm cartridge
Nice catch! Meant to put 24 Nosler
Been hearing about Bergara rifles for a few years now with bad accuracy. I've used many rifles, their either accurate shooters, i can deal with it shooters, or just junk. Honestly i dont think freebore has much to do with accuracy, since the 30 cal class has won more matches than any other class out their. Though i think the prc class will surpass the older designs due to the superior bullet construction. Though the old design is no slouch. Bullet construction and quality of the barrel have most to do with accuracy.
Could very well be a Bergara issue. As I said this is not the end all be all for accuracy
Free bore is length.
Did you watch the video? I'm specifically talking about the freebore diameter where the bullet sits before its fired
Yes, I did watch and I enjoyed it as usual. I thought some might be confused because of the difference between free bore and what you were talking about, the diameter of the chamber where the free bore is. I am not arguing just trying to clarify some points.
This was a fantastic video.
Glad you enjoyed it!
Can a 300 win mag be hand loaded to beyond SAMMI COAL, and reduce the wiggle?
The bullet can't be different size is the problem
@@ReloadingWeatherby size? Like diameter?
I'll just stick with my old BDL 30/06. Dead is dead, and it's extremely accurate with my handloaded ammo. The bullet having to jump before hitting the throat more than 20 thousands is detrimental to accuracy.
Modern cartridges for the win 🥳
I’ve noticed the accuracy issues a lot with lighter bullets. 150gn in my 300 mag was terrible, but 200gn were great. I guess now we know why… to much wiggle room.
Interesting... thanks for sharing
6.5x284 Norma vs 7mm-08?
You just going to post this on every one of his videos? Lol. I bet he acknowledges at some point.
Edit… I might be think of something else. My bad if so.
I mean mostly it is a throat dimension.
Yeah, imagine if 264Win Mag rifles were made with match chambers, which are chambers with almost no wiggle room like the 5/10000 in 6.5PRC, 264Win Mag cartridges were seated as shallow as modern 6.5 cartridges and all the powder capacity of the 264Win Mag was utilized. It would be the new IT cartridge.
😎👍👍👍😎
Thanks Mike
i like your channel Mr. reloading Weatherby, but it is time you and the rest stop calling specified clearance "tolerance",tolerance is the allowable deviation from the specified dementions in manufactering.
Moot
okay
Honestly I figured 7mm r m mag would be worse than that
PLEASE STOP calling it "TOLERANCE" when you are talking about CLEARANCE. Please get a machinists book, or look it up. You are using the wrong terms. THEY ARE NOT INTERCHANGEABLE!
Wow.. guess you're not very tolerant
It's "intolerant" for me to point out mis- information. Please take responsibility you for what you teach. I said l like your channel.
@@LBrawn Guess my sarcasm didn't come through
@@LBrawn FYI thanks for the clarification