Five More AR Builder Mistakes
HTML-код
- Опубликовано: 19 дек 2024
- Steve and Caleb from Brownells delve into a series of common errors that people often make while assembling or modifying their AR-15 rifles. This video builds upon previous discussions, bringing new insights into both upper and lower receiver assembly nuances. Here are the key takeaways:
Mounting Accessories that Contact the Gas Block: A crucial mistake highlighted is attaching accessories like bipods directly to the handguard in such a way that screws exert undue pressure on the gas block. This misalignment can lead to accuracy issues by subtly altering the barrel's position. The solution involves carefully selecting the attachment point or opting for shorter screws to prevent interference with the gas block.
Gas Block Alignment Missteps: Incorrect alignment of the gas block is another widespread issue. Properly aligning the gas block with the barrel's gas port is essential for the rifle's reliable operation. Misalignment can lead to cycling problems due to insufficient gas flow, highlighting the importance of precision in this aspect of assembly.
Over-Torquing the Castle Nut: Applying excessive torque to the castle nut can damage the threads of the receiver extension, also known as the buffer tube. The recommended torque setting is 40 foot-pounds. Exceeding this value can compromise the structural integrity of these components, underlining the need to adhere to specified torque values for optimal assembly outcomes.
Excessive Material Removal in Upper Receiver Lapping: Overlapping, or removing too much material when lapping the upper receiver, can cause the barrel to sit too far into the upper receiver. This misplacement can affect feed ramp alignment and gas block positioning, potentially leading to functional issues. Controlled lapping ensures a proper fit without affecting the receiver's structural alignment.
Improper Buffer Tube Installation: Failing to install the buffer retainer and spring correctly, or screwing the buffer tube in excessively, can obstruct the upper receiver's closure. Correct installation depth is crucial for these components to perform their intended functions, retaining the buffer while allowing seamless closure of the upper receiver.
The video emphasizes the importance of learning from mistakes and sharing knowledge within the AR-building community. Steve and Caleb encourage viewers to share their own experiences and tips, fostering a supportive environment for enthusiasts and builders. This collaborative approach aims to enhance the building process for both novices and seasoned builders, ensuring the creation of reliable and accurately functioning firearms.
Check out the first video here- ruclips.net/video/dqrd9q_brvk/видео.html
The watching from the state of Wyoming!
Maybe you should learn something about guns before you start showing videos.😮
Thanks for the 📹 !
@@BlackDogII Maybe use English?
@CalebSavant
Very sorry for the fat digits.
Caleb, blink twice if Steve beats you.
I it be the other way around... Senior abuse
Steve always 🏆wins!
👀
😂
WOW! That was funny!!! Sure it's silly but it gave me my 1st laugh of the day
To shorten any screw in confidence, first thread a nut onto it, then cut it. When you go to remove the screw, it will clean-up the threads, and you can use the nut as a mark to stop the cutting.
Excellent advice!👍
Use a nylok to keep the nut from walking
Thank you for this
Much better to shape it with a fine swiss file...
@@Jreb1865 For the finish, sure. But for the initial rough cut, this is genius.
These videos are a great resource for novice builders.
You guys are lucky. You complain about making videos. I complain about not making videos. But it seems every time I do an instructional video on an AR 15, RUclips flags at as something illegal and illicit. So I quit. They said that my video on removing milling marks on a hammer for an AR was an illegal act. I just can’t argue with that kind of stupidity anymore. Keep up the good work guys. While you can.
Freedom of 💬 speech!
I get comments removed, and I get "time outs." My comments are way more polite than many that I have seen.
The AL Gore has no rhythm targets Christians, 2A, and Conservatives!
Good luck, my friend. Keep on trying.
Happens to me all the time.
Fun Fact: : RUclips is run by the Deep State CIA. They collect and manipulate intel on everyone. Time to go to the dark net -everyone.
I feel your pain brother...that's why I retired...commie-tube at its best.
they are talking about it. if your showing.... its a no no...
watching you guys makes me feel like im sitting there with you having a genuine conversation 😆
You guys are the most genuine people I see on RUclips THANK YOU
Gotta love the comedy duo of Steve and Caleb! Time to take the show on the road!
Thanks for this one. Your first mistake was one that made me think. I have a Ruger MPR AR556 model 8514 with the rifle length gas system. After watching this, I went and looked at it, and sure enough, the screw that held my front QD point in place was jammed up against the gas block. It was a quick fix, but I have a feeling I'm going to have to re-zero the optic. Keep up with what you're doing, these videos are so informative.
You probably will, not because the optic was "not zeroed" but because the barrel will never be consistent with something pressing up against it like that.
And it can change barrel harmonics
yer biggest mistake was buying a pos ruger.
@@notlisted-cl5ls feel better now? I hope so.
Even though you guys aren't father and son haha I appreciate how brownells cleverly put a old school and new school gunsmith together to collaborate the best of both worlds, good job brownells I love this show.
With gas blocks that have Allen screws, you can remove the screws then turn the block up side down and look through to see where it needs to be placed front to rear. They drill the gas port using the rear Allen screw hole so it's perfectly aligned. On some barrels they leave room for the A2 handguard backing plate that is around .0050 thick, that in return allows the gas block to be to far to the rear. On most barrel gas block combos it's not a big deal, but should be checked to achieve perfect alignment. I hope this helps.
They drill the simple using the gas port as a reference, not the other way around. The gas port location is referenced from the index pin on the barrel extension.
@@sluttybuttHe's talking about the gas block port, not the barrel port..
Yes, I always use that trick to double-check fore/aft alignment/pencil-mark the shoulder for centering the already-installed gas tube before drilling dimples for the set-screws.
mil-spec ejection port dust cover: forgetting to install BEFORE the barrel nul.
At that point. Suck it up. Go buy a Magpul port cover.
😅
Yuuuuuuup. Damnit.
Partially why I went to those poly covers....
I have all my lowers built moving into the uppers and man you guys gave me the masters cut on how to build like a pro!!!
I swear yall give me batman and robin vibes, or kinda like mr rogers and robin honestly 😂 love the brownells content, has helped me learn and perform quality work on my guns at home
Mistake #1 was worth the price of admission. We had a guy do something similar last year with a Chicom "M-lok" vert grip and it took me FOREVER to figure out why the gun wouldn't shoot straight. Well done, gentlemen.
May I ask. Was it Strike Industries?
As you tighten the castle nut, it turns the tube as well. Clock the buffer tube at exactly 6 oclock. Endplate does not center or align it by itself, the tube still has some play, so you must center it.
That nub on the end plate that interfaces with the lower keeps it from moving, there isn’t really a way to “clock” it
I find that having a buttstock/brace installed helps visually with final alignment. There's not much play there but it's enough to cause easily-visible over-rotation if you lock it down and expect the end plate to locate it properly.
Uncle Steve and cousin Caleb
It’s good to see you fam.
The last comment Caleb made.... 🥁 😅 The comedy in this video, I literally seen Steve jump and almost spit his coffee across the room....lol
RUclips is great! And Brownels has some of the best AR build instructional videos here. I shot a rifle once about 37 years ago - and had never seen an AR, until I built my first one. I have built a few others since then, and no problems so far. Thank you for the videos tips and advice.
Thank you Steve and Caleb, another well explained and clear video that will help many. Steve's videos a few years ago taught me how to service my dad's SKS. Wonderful videos and a wonderful place to buy from.
Yep, the buffer tube in too far was my first time mistake. Wound up shearing off the buffer detent trying to get it back apart, easy fix and learned from it. On another, I simply had issues with the upper and lower not aligning, had to remove some material from the lower, file the sides of the upper lugs and the pins are still tight as can be- mallet and drift pin to remove them. I suppose tight is better than loose and it runs fine. Good video, great advice.
I've heard many other Gunsmiths and manufacturers state there must be a gap between the gas block and shoulder of the barrel.....
More importantly, make sure the gas port lines up 100% with the hole in the gas block... I bought a simple plastic tool that helps to achieve this: the gas block genie.
Here's our stance on it- ruclips.net/video/H8EEUIRd8HU/видео.html
The appearance of the gap is irrelevant. Gas port just needs to be aligned on the inside. i just buy a 99 cent packet of dry spaghetti.
@blantant I was thinking more about heat/ expansion/ contraction and keeping "undue forces " off of the barrel shoulder.. not so much regarding the appearance
If you're super concerned then install it correctly and check with a borescope that has a mirror adapter.
You’re right. Not all gas blocks are the same, or meet the manufacturer specs. Same for barrels. Not all gas ports are the proper distance from the shoulder, nor are they centered. You can’t just assume every single one is perfectly within spec, and use the shoulder as a datum. Maybe use it for a starting point, but it should be verified and checked to be centered over the gas port.
I love the setting and atmosphere the videos have. Steve and Caleb’s personalities and demeanor work!! These videos are a must for any 1st time or hobby builder. Keep up the good work guys.
Spot on, gentlemen. I had to go back and redo a few of these little assembly jobs on my first build. The main thing I learned from that first build is to do myself a favor, go full "nerd", and put together an engineering process management series of steps in an Excel Document (or Word doc) with all details needed (fps required for each nut/screw/etc.) to complete an AR build. Once that's done, I could begin executing my steps one at a time until the build is complete. 30 AR builds later and it's now second nature. Bonus tip for anyone who doesn't already know: spring/detent work should be done inside a pillow case or under a bed sheet that will catch flying springs. "Spring slinging" happens to all of us every now and then (even expert AR builders). Better to have a pillow case because small springs in a small or large room = lost springs.
Says you. I’ve shot my spring and detent across the room, found it in the kitchen under the stove, immediately did it again, found it under the dining table, and finally installed it. I promise you I can find any detent, even in the carpet
@@jeffpraterJSFI once found a detent in my master bedroom. I’ve only ever assembled in the garage…so somehow that little guy made it upstairs and buried into the carpet. Still not sure how 😂
Was hiding in your shirt
@@hueco5002
After building literally hundreds of ARs, I buy extra springs and detents.
All I have to say... your poor wife...😂
Good video guys. The error I made on my first build was I had the hammer spring oriented incorrectly. Worked fine the first hundred rounds or so, then light primer strikes. I also got practice finding detents on my garage floor.
Ok, im loving how entertaining you guys are, blasting on each other. And good knowledge also. Thanks
I made the same mistake with over inserting the buffer tube on the first one. Fortunately it didn't take long to figure out the problem. Good tips!
Regarding the omission of the buffer spring retention pin and spring, if you're using a JP Enterprises silent captured recoil buffer spring assembly, you're going to WANT to leave those two small parts out of your build, or you will blaspheme to no end trying to get your buffer spring assembly out for cleaning or adjustment. Ask me how I know.
it can break and fall into the fire control group too
I am an armorer and have built more AR and large frame ARs than I can count. One of the mistakes I see a lot are people not degreasing and greasing threads as they build. The technical manual is a good start, but is years behind in the evolution of these products. Most parts come with a preservation grease on them designed to protect the part, it is not for functioning. Use some denatured alcohol, degrease the part, then toss a little oil on the threads. This works for the mag release, receiver extension, Aeroshell on the receiver threads, etc.. Also, do a test fit prior to installation.
The only grease I ever had to worry about was upper threads and barrel nut.
@@whatsmolly5741 cool
To your first mistake, I found that even if your screws do not contact the gas block when it's mounted, if it's not far enough away, you will still get contact later when you're shooting due to barrel whip. So it's important that you either cut your screw short enough to avoid that but it's still probably better to just move your attachment enough to fully clear the block.
I have always wondered about the spec of approx. .003" between the gas block and the barrel lip. I've never questioned it, just grabbed a business card and used it as a gauge to space the gas block away from the lip. I guess whatever works. Thanks for the great video- I love this subject!
Use the barrel dimple and and it takes all the guess work out of where to align it.
Get a gas block dimpling tool. Done
@elzippo488 Not all barrels are dimpled. In the past, I’ve used a borescope to verify alignment. Recently bought a dimpling jig. Worth the money, although you have to buy multiple jigs to fit different barrel diameters.
IIRC, the thickness of the handguard end cap is around .020”, not .003”. Business cards range from .020” to .030”, so should be close enough.
My 1st build I ruined my buffer tube threads but since then ive learned correct build practices and bought necessary blocks & jigs
Built my first AR when I was 18. My first rifle I bought with my own money and it’s still running great 7 years later.
Best AR-15 education available. Thanks guys!
Yeah, I saw a video where a guy had a gas port drilled a little further away from the shoulder of the gas block journal. He had to push the gas block back between 1/16th and 1/8th of an inch. I always check that now. A good way to check distance from the shoulder is with the pin at the bottom of most calipers. This will allow for measurement to the hole and even the diameter of it.
I built 2 AR's already and I did not make any mistakes because I watched Caleb's videos on how to build an AR...... LOL!!
This episode was a delight.
I never built an AR platform ever until a few years ago, I watched the video of Larry Potterfield of Midway USA on how to build one and it was so easy to follow and built my first AR with no problems!
Sorry to here that..
I always appreciate these informative videos you two make. Keep it up, we love it!
I use a lot of Ballistic Advantage barrels mostly the Hanson profiles! Clint has a video that he states you run the gas block all the way against the shoulder! I use a borescope to confirm mine and he is right and so are these guys!
It's the correct thing to do for barrels that have not accounted for the possible use of a handguard retainer, such as your Hanson barrels. Most barrels, however, leave room for the retainer, and for perfect alignment, would need a space that exact width if one isn't used.
That said, most gas ports (especially 223/556) are considerably smaller than the corresponding hole inside the gas block, and the average 556 gas port (≈0.07- 0.09") will still fall entirely within the roughly 0.125" opening in the gas block. And though it's not something you mentioned, but rather something stated in the video about carbon build-up if there's misalignment, I highly doubt that will be a consequential issue, as the pressure and temperature at the port will flame cut the barrel.
Video on how to pin and weld muzzle device please
IV8888 has a good video on this subject.
@jcarne1015 thanks
Every castle nut I’ve torqued to 40 ft-lbs. has sheared the teeth off. I’ve purchased 3 different wrenches for the job too. Were all the nuts just junk? They appear to be cast. Great videos. Love your tips. Please keep them coming!
Yes, or you were torquing them way more than you realized. Did you use a breaker bar or adjust for handle length?
I made the last mistake in the video. I didn't screw the buffer tube in enough to trap the buffer spring retaining pin in place... needless to say my AR did NOT run. It's surprising that that little pin not being where it's supposed to be can cause a hell of a jam. I had to slam the buffer tube on the shooting bench just to get the bolt carrier to move back.
Great videos, guys. Much love from Missouri
brotherhood of ears lol.. love you guys keep it up
I appreciate the humor and knowledge
I couldn’t find out why I couldn’t sight in my .300. I had a Mlok screw driving the barrel to the left ever so slightly. Palmetto State makes some excellent handguards. However, a lot of them are super close to the barrel. Look Out!
I bought an upper from someone that installed a rail that touched the gas block. The gun shoots great! On the good side of the problem, I got the upper for cheap!
Always run off shoulder .025 to center gasport. Do it right or don’t do it all, most of time it won’t effect gas on high pressure rounds but it will make a difference when running subsonic especially if factory barrel gasport is smaller. All my 300 blackout and 7.62x39 builds are port matched to Gasblocks and centered correctly this allowing 100% of gas to be utilized.
The hole in the gasblock is larger than the hole in the barrel so it will get 100% of the gas regardless. More info on that can be found here- ruclips.net/video/VH_fZNldI4o/видео.html
@@CalebSavant it will not on subsonic loads. If you do not have all the gas, I had a 7.62x39 that would not run subsonic suppressed. There was not enough gas due to 40% of the gas block covering the gas port.
@@ngaoutdoors4157 I get what you're saying and I agree, but look at the video I linked.
Great information, I found one of my AR's foregrip has a screw that I am am gonna need to shorten, thanks.👍
My grandfather use to say, learn from others mistakes it hurts less
Thanks for the great videos and instruction
Give em hell fellas! Those of us who are too ignorant to know what we don't know thank you for your work!
On my first AR build I put the castle nut on backwards. A little difficult to tighten, but it stayed that way until recently.
Had the gasblock issue with a micro clamp-on but gb touched the handguard. Swapped it out with bcm dimple on. So check that too.
Great video, love the honest interplay!
I did the same thing mounting a forward grip that pressed into the gas block, making the barrel no longer a free float barrel.
I don't know if you guys covered it in previous videos but perhaps a talk on buffer springs/buffer systems? I know they've been covered in individual videos (I watched the A5 video before deciding to buy it) but a quick rundown of rifle vs carbine vs A5 in a single video might be helpful for folks building a new rifle. After using an A5 setup in a rifle that was previously carbine, I intend to replace all of them with A5's. Going to cost some money but it'll be worth it IMO.
00:11:50 How do you safely/properly lap the receiver?
I did good for my first AR15 build but ran into an issue matting the lower with the upper. Found that the tension screw (green) was way too high. Lower the tension screw and it mates perfectly and I can now lock in the rear pivot pin.
Great stuff gentlemen
Info I've researched in years past on AR building was to use a business card to space the gas block from the barrel shelf
I learned the lesson to clean before use. I bought a brand new fully assembled Colt upper w/ BCG. I slapped it on a lower I'd assembled and took it out shooting. It did not want to fire. At first I assumed the problem must have been the lower, since that was the part that I had put together. Nope.
I found that the BCG was packed with grease. It was so thick and sticky that the firing pin couldn't protrude all the way. So clean and inspect before use.
Had a similar problem with an Alexander Arms upper, but it was the opposite direction: the grease they used had polymerized and jammed the firing pin *out the front of the bolt face.* When I closed the bolt on a round the stuck firing pin set it off. Fortunately I was following the 4 Rules and the gun was pointed in a safe direction and discharged into the ground in front of me, but having an accidental discharge like that was *quite* surprising.
I contacted AA about the issue and it turns out they already knew about the problem with the hardening grease and had a safety notice about it, as well as had contacted all customers for whom they had contact info for. I, unluckily, was not one of those. The solution was to thoroughly clean off all the old grease and re-grease with something that would not harden (so basically any quality lube you chose to use). They had already dumped the questionable supplier and were running something else by the time I contacted them, so new products would not be in a similarly dangerous situation. It was a very easy fix to a very dangerous problem.
But yeah, the 4 Rules people, they are important even if you think you have everything under control. Sometimes actual accidents do happen.
I understand lapping the upper, but what if the barrel extension edge isn't flat? Oh and I think it would be fun for you guys to have a little competition on building a rifle, bolt action, each of you go through the builds and explain why ya'll choose the parts and then to the range.
After having a buffer retainer break where the small tip breaks off and gets in a trigger cassette jamming it… I’ve stopped using the buffer retainer and spring. I do have a Jack-in-the-Box every time I split the receivers, but I’m ready for it.
If the buffer retainer breaks, your rifle is out of spec..You should fix it rather than leave the buffer retaining pin out..
You're definitely a PSA owner
Agree on learning from "mistakes"!
My 1st ar smithing was from getting a new complete ar upper 556. The gaskey machine bolts weren't peened properly and ruined the key and the gas tube. Love fixing my guns myself.
No warranty?
I’ve screwed the reciever tube in before I put the small spring and retaining detention in. I went to far and had to back it out two four turns to get them in. Then screw it twice to hold them.
I've got a good one for you guys....
Putting the plunger in first then the spring when putting in the bolt catch.....
Thanks for the free knowledge. Not sure if you covered it once before, but what is the best way to align the gas block to the barrel?
Use the SLR dimple gauge and verify with a bore scope..
He may not be your father, but he’s definitely your Daddy 😂😂😂
Another great one guys!
Love these two!
One thing I have never thought of, and in dozens of builds have never had happen. Found out the hard way that it is so simple but one of the Worst *Simple* Mistakes I have made because now That Lower Receiver is useless to me (and it is a nice one that I was looking forward to using) When installing the Front Pivot Pin in the Lower Receiver, I accidentally dropped the Detent In First - and Then the Spring. Used my tool to compress it to get ready to install the Pivot Pin. And now I have a Detent STUCK in the bottom of that skinny hole, and have been racking my brain for almost a year thinking of ways to get it out. Ordered a Tiny Cylindrical Magnet, but if it were loose enough to come out That way - it'd probably just have came loose with a Whack. It is in there pretty tight and dammit, I really want to use this Lower for a Build already. Don't make this mistake... ((ALSO>>> Any suggestions are certainly welcome))
Knowledge isn't always free, but it is better than gold
How do you avoid over torquing the muzzle device to get it timed/alligned properly. What are problems caused by over-torquing?
I’ve seen a significant loss of accuracy result from over torquing a muzzle device. Best way, IMHO, is to use a peel washer, and shim it so it aligns without exceeding the specified torque.
I accidentally over torqued the A2 flash hider onto my barrel and it crushed the crush washer so it's stuck on the barrel. That's one potential problem.
Consider getting the mounting rail tacked on if possible.
These two have the best job ever
Derailed me , screwed up , the puns were coming fast today .
I was about to ask what's in the cups , so thanks for answering my question .
I think in machinists' term its call "facing" the receiver. Lapping meaning using lapping compound or abrasives to smooth out the inside diameter of the receiver.
How do you keep the buffer tube perfectly aligned up and down while torquing the castle nut?
Buy a jig that aligns it and holds it in place while torquing the castle nut. There are pricy ones, for high volume builders, and cheaper ones that can be sufficient with a little tweaking.
Damn I had the screw pushing on the gas block…
Thank you 🙏
How they’re not father and son is beyond me. Look at the ears.
You can't miss the ears, it's the first thing I noticed. They have about the same hairline too and noses.
@@melissasmess2773 yup, all of that! 😁
🤣🤣🤣 I noticed that too, when they said that they're not related, I started looking at the facial features and then noticed that their ears looks either the same or very similar. 🤣🤣🤣
They heard you think this
Damn you guys got em pegged as the dumbo bros. I've seen rubber bands , I ain't ever seen no elephant fly! Lol
I never use a drill.I always do it by hand just the right amount ma'am works every time
Still wanting Brownells to do an AR builders class.
love to watch Steve's face get red... thanks fella's
I've seen a few people install their flash hider/flash suppresor/muzzle brake upside down or sideways.
Appreciate the video guys.
I m glad Caleb pulled out the gas block, and not somethin else.
That last one made me laugh. My first AR was a PSA build-it-yourself kit that a friend put together and wanted to get rid of. The first time I took it apart the buffer went flying across the room. Fortunately it was an easy fix the castle nut was only hand tight!
happy to say that none of this has ever happened to me....however getting the pin into the gas block top has given me fits for sure.
Great episode!🤙🏽 Anti-walk pins necessary?
Great job guys!
I had an interesting gas block failyre that presnted like a misaligned gas block.
I had a gas tube and gas block that didnt seem to want to allow the roll pin to slide through.....so i used a slightly small drill bit, turned by hand, to remove what i thought was a slight burr in the gas tube pin hole. The problem actually turned out to be that the pin holes in the gas tube or block were misaligned slightly, so the tube was slightly misaligned in the block....caucing a small but persistent failure in a 233 wylde.
Lesson, dont force the parts to align. If they dont align right away, replace them.
I like how it seems they make these videos with one take so some of their antics can be caught: "You had just derailed me."
it was a hidden pun, he was talking about rails...
@@bigblockchevy2294 Hah okay. I can be dense sometime. Tango
@@MavHunter20XX i don't think he knew he made a pun. for sure he would've called it out. nope, that sailed right over Caleb's head. swoosh!
Great advice, guys. I especially like the part regarding the receiver extension/buffer tube. I'm guessing you have to use an offset adapter - like a "crow's foot" wrench, as I know them - with a torque wrench in order to torque the castle nut to specification? But isn't there a formula necessary to apply when using an offset adapter w/a torque wrench? When I worked on nuke warheads while in the Army, we had to use a formula if an offset adapter had to be used due to a slight difference in actual torque applied:
M1 = M2 x L1 / L2. (You can look up the formula breakdown).😉 It goes w/o saying exacting precision was of utmost importance.
The crows foot wrench has to be with the square of the torque wrench facing you and with he wrench straight up to the left or to the right, 9 o'clock or 3 o'clock, if it is at the 12 o'clock position then you will not get the correct torque.
Who makes the best castle nut wrench?
Me, its 5 grand, want to order one?
Is there a good way to clean the carbon out of your gas tube and gas block without removing the gas tube ?
An ultrasonic cleaner or soaking it in carbon remover. Then blow it out with compressed air
I never had to clean out a gas tube. I have a 84 colt with about 10,000 rounds. replaced gas tube about 9000 rounds because the carrier end of tube was showing excessive wear. The velocity of gas keeps them clean.
I just replace a gas block on a AR15 because it was just barely touching. Built a AR10. I chose a bull barrel stainless bull barrel. The barrel nut had very sharp burrs on the inside. Scratched up the barrel. Ballistic Advantage was nice enough to bead blast it again. And I used a jeweler’s file and cleaned up the inside of the barrel nut. Just had to thread in a buffer tube one more turn on a brand new AR10. Buffer retaining pin was barely catching the edge. Not it holds it and moves freely.
If an upper receiver is over lapped, you can shim between the upper and barrel flange..