Is bedding the AR barrel a myth? What's the best way?

[PappyM3]

...

Handguard pressure moves MPOI, even with the beefy Seekins/Aero uppers. It's worse with M4 uppers. This can be vertical or horizontal. For example I had a .15-.20 mil shift between bipod and bagged on a barricade. A coworker's rifle was closer to 0.35-0.40 mils. Inducing torque from uneven bipod landing caused horizontal shifting.

....

So, you're saying you saw measurable POI shifts when applying force to free floated handguards? Presumably from force being enacted on the barrel nut and therefore onto the barrel. Was this noticed with receivers that had been trued and bedded or interference fit barrels? I may have to do a test with my Service Rifle, one group with full sling tension and one group on a rest.

And yeah, with standard M4 uppers, you'll generally get about a 1 MOA POI shift for every pound applied to the handguard. The USMC shooting team did a study. I believe standard M16s experience ~2 MOA POI shift for every pound applied to the handguard.

I'd be curious if Larue's proprietary receiver/handguard setup completely negates this. It seems as though the handguard is strictly attached to the upper with nothing touching the barrel nut. While they come out with some ridiculous "innovation", sometimes they do have good stuff.

 

[Ledzep]

So, you're saying you saw measurable POI shifts when applying force to free floated handguards? Presumably from force being enacted on the barrel nut and therefore onto the barrel. Was this noticed with receivers that had been trued and bedded or interference fit barrels? I may have to do a test with my Service Rifle, one group with full sling tension and one group on a rest.

And yeah, with standard M4 uppers, you'll generally get about a 1 MOA POI shift for every pound applied to the handguard. The USMC shooting team did a study. I believe standard M16s experience ~2 MOA POI shift for every pound applied to the handguard.

I'd be curious if Larue's proprietary receiver/handguard setup completely negates this. It seems as though the handguard is strictly attached to the upper with nothing touching the barrel nut. While they come out with some ridiculous "innovation", sometimes they do have good stuff.

Yeah I saw about the same POI shift before and after bedding the barrel. No experience with shrink fit. My Seekins upper was not a press fit to begin with.

The same shift could be seen across various ranges until the MV spread started turning into vertical that eclipsed it. But the general plan was that my 4DoF file was lined up for a bipod, and I would add 0.2 mils for barricade positions.

 

[Ledzep]

Left/right favor was from me to separate them.

 

[Gohring65]

This thread has me wondering if 620 loctite would help sloppy fitting remage threads.

 

[45-90]

The barrel extension spigot


Odds are that even after truing the face the bore is conical. It's pretty unlikely the face looks like that and the bore is strait.

The bore has nothing to do with the face, as its a separate machining operation. It could be tapered, out of round, off center, etc with a host of problems. But it's not. This is typical CNC production product. And there are faults here that I recognize, one is programming. It depends on how it's fixtured, as to the accuracy of any secondary cut on a so called finished part. Here a ground fixture rod is inserted in the bore for a snug fit, all the way through the bore...so it is straight, even with slight bore imperfections.Then turned in a lathe centers.
In this setup it is totally perpendicular to the bore and perfect as humanly possible. And can even be measured on a granite surface plate for purpenducularity. It's possible to make a silk purse out of a sows ear...do it constantly with many of today's shooting products...dies, chambers, muzzle brakes, etc are all re machined or altered.

 

[Ledzep]

This thread has me wondering if 620 loctite would help sloppy fitting remage threads.

Probably not as much as some torque might... IF you're experiencing dispersion issues.

 

[ironman56]

After reading this entire thread , I decided to shim the barrel on the new AR10 308 build I'm doing , all the parts came in today and I ordered some shim material two days ago and it came today too so it was good timing. The .0015 was the best fit , with about 7/8 wrap around the extension, had to tap the barrel in the last 1/4 inch with a rubber mallet . I didn't true the receiver face as I don't have the tool for the large frame AR , got it all slugged up just waiting on the reaction rod for 308 to get here from brownells so I can torque the barrel nut , then finish up and head to the range for a test run , my first AR10 build.

 

[Earnhardt]

Like others have said…
A light lapping.
Then Loctite 620 on the barrel extension…
Works great.

 

[FredHammer]

I'd have to dig through several hundred test results to find it, but I did this test in our 200yd tunnel and in my rifle it made an immediate and apparent difference.

This is off of memory, but the rifle was shooting roughly 2.5-3" groups (20 shots, 2x 10 shot strings) at 200yd and after bedding the barrel it was in the 1.8-2.2" ballpark.

Also, adjusting gas settings makes a difference for mean radius through the occurrence of errant fliers (lowest gas to reliably run the gun is best). Gas setting also moves MPOI. This is worse the longer and skinnier your barrel. .936" GB is the only way if you really want consistency.

Handguard pressure moves MPOI, even with the beefy Seekins/Aero uppers. It's worse with M4 uppers. This can be vertical or horizontal. For example I had a .15-.20 mil shift between bipod and bagged on a barricade. A coworker's rifle was closer to 0.35-0.40 mils. Inducing torque from uneven bipod landing caused horizontal shifting.

In short, the AR was designed to be a light weight battle rifle, and the pursuit of precision is an after-thought full of bandaids. Someone should make an M-lok/ARCA AR-15 lower in the same vein as that Springfield Armory rifle with the extendo fore-end lower, and someone should make 316 or 416 Stainless press-fit uppers to go onto said lowers if you want to keep AR-15 commonality for small parts but use the rifle for pure precision. YMMV.

Now I see in the Seekins video, the Seekins guy saying bedding doesn't matter.
Oh golly gee, might he be saying that to push their product?

 

[supercorndogs]

This thread has me wondering if 620 loctite would help sloppy fitting remage threads.

You have a barrel from McGowen? Might want to get those threads checked. They sent me three with undersized threads on one or both ends. My barrels form Crietrion, crown ridge, PVA, and Apache Gun Works all fit my actions well.

 

[Gohring65]

You have a barrel from McGowen? Might want to get those threads checked. They sent me three with undersized threads on one or both ends. My barrels form Crietrion, crown ridge, PVA, and Apache Gun Works all fit my actions well.

As a matter of fact, the one sloppy prefit is a McGowen. It’s been about five years since it’s been installed and it throws a flier. It’ll stack 3-4 shots in the same hole and boom 5th shot an inch away.


Edit. Scratch that it was a mcrees precision barrel. I mixed those two companies up, my mind is warped from my lifestyle in my 20s. Lol

 

[KCode]

Can anyone critique this guy's process?

 

[XP1K]

I agree, and if you have a rifle that spits good groups with a semi cold barrel but starts throwing fliers as it heats up, then it would probably benefit from truing the face and shimming/bedding.

Hmm, this kind of makes me want to pull my MK216 PWS apart and check the fit. Through various load development and shooting factory FGMM, it'll pile the first three in together all touching, #4 will usually open it up just slightly, then #5 will open the group up to 1moa or just a touch over.

It's been a long battle with this gun. I've tried so many different buffer and spring combos and tweaks with the gas system but I've finally found a combo with it that shoots and isn't terribly hard on brass so I'm kind of reluctant to mess with it.

Top group, three rounds in there, 250 yards shot cold, prone off a bipod and rear bag. First two just left of the hole third shot is either right above it or went through it. Knocked the target off the hanger.

This one was three hundred yards. Cold, same setup. I don't shoot this rifle a whole lot and it's taken me quite a while to get a feel for the right amount of preload on the bipod. It doesn't like much. I shot a jug at 300 after the silhouette and preloaded a little too much, pushed the impact up about .75moa.

 

[Gohring65]

Hmm, this kind of makes me want to pull my MK216 PWS apart and check the fit. Through various load development and shooting factory FGMM, it'll pile the first three in together all touching, #4 will usually open it up just slightly, then #5 will open the group up to 1moa or just a touch over.

It's been a long battle with this gun. I've tried so many different buffer and spring combos and tweaks with the gas system but I've finally found a combo with it that shoots and isn't terribly hard on brass so I'm kind of reluctant to mess with it.

Top group, three rounds in there, 250 yards shot cold, prone off a bipod and rear bag. First two just left of the hole third shot is either right above it or went through it. Knocked the target off the hanger.
View attachment 8274259
This one was three hundred yards. Cold, same setup. I don't shoot this rifle a whole lot and it's taken me quite a while to get a feel for the right amount of preload on the bipod. It doesn't like much. I shot a jug at 300 after the silhouette and preloaded a little too much, pushed the impact up about .75moa.
View attachment 8274262

Like others have stated, I’ve never seen it hurt a rifle’s performance. It’s a relatively cheap process too.

 

[KCode]

So I've been looking into this shim thing and you guys correct me here if I'm wrong...

You place the shim on the extension and try to push it in. If it crinkles then you have too much and need to remove some. You keep doing this until it is a tight fit and you need to lightly tap it in with a mallet.


My theory, and again correct me if I'm wrong here. My theory is you find where the shim is too thick and you start to crinkle it. You then heat up the upper and thermo fit the extension and the shim that is too big. In theory this will insure a tight fit even when you have a hot barrel.

Thoughts?

 

[Gohring65]

So I've been looking into this shim thing and you guys correct me here if I'm wrong...

You place the shim on the extension and try to push it in. If it crinkles then you have too much and need to remove some. You keep doing this until it is a tight fit and you need to lightly tap it in with a mallet.


My theory, and again correct me if I'm wrong here. My theory is you find where the shim is too thick and you start to crinkle it. You then heat up the upper and thermo fit the extension and the shim that is too big. In theory this will insure a tight fit even when you have a hot barrel.

Thoughts?

This is what mine looks like when I do the whole procedure. I order stainless shim stock in various thickness and I start something like a .002” shim and lube it up with 620 loctite and try it with heating the upper, if it slides in without crinkling the shim I set it and tighten the barrel nut to seat it fully. If it crinkles I go down to .0015” and then .001” until I get it to seat good. The bad part is each try I have to spend a little time cleaning up the loctite before I try again. I don’t like the idea of cutting material away from the shim to make room, the 620 might fill the gap and one decides to just cut some of the shim to maybe only wrap 80% or so around the extension, I feel like it could move in the direction of the 620 filled gap when it starts to heat up and might make the loctite malleable.

 

[KCode]

How hot are you getting the receiver? Are we talking a torch or a hair dryer?

So you're really going to town with the shim and almost a full wrap.

 

[Gohring65]

How hot are you getting the receiver? Are we talking a torch or a hair dryer?

So you're really going to town with the shim and almost a full wrap.

Yes, the more I have wrapped the better I feel. The 620 will fill all the little gaps that’s left. I have used a heat gun and a torch. It doesn’t take much heat, a hairdryer might work, but not sure. With a torch I don’t spend much time in one spot, and I don’t put the flame tip on the upper.

 

[KCode]

Yes, the more I have wrapped the better I feel. The 620 will fill all the little gaps that’s left. I have used a heat gun and a torch. It doesn’t take much heat, a hairdryer might work, but not sure. With a torch I don’t spend much time in one spot, and I don’t put the flame tip on the upper.

Curious if you think this would discolor an anodized receiver in a color other than black.

 

[FredHammer]

How hot are you getting the receiver? Are we talking a torch or a hair dryer?

So you're really going to town with the shim and almost a full wrap.

In armorer's school the instructor said if the aluminum turns white, you are too hot! This might be the only case in the known universe where white isn't always right!

 

[Gohring65]

Curious if you think this would discolor an anodized receiver in a color other than black.

Good question, I doubt it, but not sure. Maybe someone can chime in that’s done it with other colors.

 

[KCode]

Good question, I doubt it, but not sure. Maybe someone can chime in that’s done it with other colors.

I couldn't imagine a hair dryer doing it. I'm not sure about a heat gun but probably not. Torch....Ehhhh if you're not careful maybe

I just want to understand how hot to get the end of the receiver for a thermal fit.

 

[Gohring65]

I couldn't imagine a hair dryer doing it. I'm not sure about a heat gun but probably not. Torch....Ehhhh if you're not careful maybe

I just want to understand how hot to get the end of the receiver for a thermal fit.

I agree with you on your theory. I’d say if someone has doubts, just go to harbor freight and pick up a cheap heat gun. I don’t think anyone could do any damage with a heat gun. With a torch I put maybe 10-15 seconds with the torch. Not long at all, it’s pretty thin aluminum it’s doesn’t take long for it to expand enough.

 

[FredHammer]

I couldn't imagine a hair dryer doing it. I'm not sure about a heat gun but probably not. Torch....Ehhhh if you're not careful maybe

I just want to understand how hot to get the end of the receiver for a thermal fit.

Hair dryer - No
Heat gun - Yes, a more steady delivery of heat that allows for some fuck up, but can deliver the heat in a manner that heats up the surrounding parts because its slower.
Torch - Fastest, but fasted to fuck up. But it is quick and directed at the part to be molecularly changed. I've not torched colored anodizing, but plenty of black anodized with no ill effect. Anodizing is anodizing by the definition. It's some electrolysis procedure that changes the colors of the parts by manipulating the level of current to the parts. SO, if "black don't crack" I don't think the other colors will either...

You are only heating the threaded portion and for not a very long amount of time to excite the molecules in the aluminum. 5-6 seconds ish.

 

[KCode]

How much time do you get to get the extension in before the receiver closes down due to cooling off?

Also where are you guys getting your shim stock?

 

[PappyM3]

Can anyone critique this guy's process?

He seems like a good dude, for one.

A few things:
- First and foremost, he’s using a bargain bin PSA barrel and shooting basic non-match ammo. All of his precision testing is within the noise for the barrel and ammo combos. None of the results can really tell us anything.

- He’s not actually doing a thermal fit. Just shimming to make it a little more snug. It should provide some benefits (and I do it for non-match rifles) but not as much as a thermal fit. He mentions this in his conclusions.

- He’s focused on centering the barrel to the bolt, which is good, but it’s only part of why this is all done.

- Loctite 638 is higher strength than 620, but lower temp. I’d go 620, the extra psi of sheer strength isn’t needed. Its main purpose is filling gaps. But this isn’t a big deal between them. 638 is higher temp than 609. However, looking at the specs and 609 may be better when doing a thermal or press fit if you want to do both the interference fit and also add the loctite. It works well up to 0.15mm gap (6 thousandth of an inch). Whereas 620 and 638 work from 0.15mm to 0.25mm. That said, I haven’t seen 620 fail to cure in spaces smaller than 0.15mm.

How hot are you getting the receiver? Are we talking a torch or a hair dryer?

So you're really going to town with the shim and almost a full wrap.

Heat gun, 100%. I doubt a hair dryer will get hot enough and a heat gun is much easier to avoid overdoing it than a torch.

With the heat gun, I keep working it until the receiver face is too hot to touch for more than a moment. I’ve never used an infrared temp sensor or anything. It can cool fairly quickly, so have your barrel on hand in front of you to slide it in, but you don’t need to rush like a madman.

 

[FredHammer]

He seems like a good dude, for one.

A few things:
- First and foremost, he’s using a bargain bin PSA barrel and shooting basic non-match ammo. All of his precision testing is within the noise for the barrel and ammo combos. None of the results can really tell us anything.

- He’s not actually doing a thermal fit. Just shimming to make it a little more snug. It should provide some benefits (and I do it for non-match rifles) but not as much as a thermal fit. He mentions this in his conclusions.

- He’s focused on centering the barrel to the bolt, which is good, but it’s only part of why this is all done.

- Loctite 638 is higher strength than 620, but lower temp. I’d go 620, the extra psi of sheer strength isn’t needed. Its main purpose is filling gaps. But this isn’t a big deal between them. 638 is higher temp than 609. However, looking at the specs and 609 may be better when doing a thermal or press fit if you want to do both the interference fit and also add the loctite. It works well up to 0.15mm gap (6 thousandth of an inch). Whereas 620 and 638 work from 0.15mm to 0.25mm. That said, I haven’t seen 620 fail to cure in spaces smaller than 0.15mm.

Heat gun, 100%. I doubt a hair dryer will get hot enough and a heat gun is much easier to avoid overdoing it than a torch.

With the heat gun, I keep working it until the receiver face is too hot to touch. I’ve never used an infrared temp sensor or anything. It can cool fairly quickly, so have your barrel on hand in front of you to slide it in, but you don’t need to rush like a madman.

Or do we forego all this and do what Seekins dude says?
Damn it you all. Now I got an Aero M4E1 enhanced in the shopping cart...for science...
...and I was just notified one of my creations just dropped a buck. Waiting for full kill report!

 

[Gohring65]

Or do we forego all this and do what Seekins dude says?
Damn it you all. Now I got an Aero M4E1 enhanced in the shopping cart...for science...

I want to do a M5 enhanced next but I wonder about getting the shim installed right thru that interface. I thought though I’d just glue it with 620. I’ve never seen a m5 enhanced in person, maybe I’m overthinking it.

 

[FredHammer]

I want to do a M5 enhanced next but I wonder about getting the shim installed right thru that interface. I thought though I’d just glue it with 620. I’ve never seen a m5 enhanced in person, maybe I’m overthinking it.

HAHAHA! My exact thoughts on the enhanced. "Welp, the interface is set deep in there. So, I shoot and see, then loc-tite, and shoot and see!"

 

[redneckbmxer24]

Now I see in the Seekins video, the Seekins guy saying bedding doesn't matter.
Oh golly gee, might he be saying that to push their product?

According to Seekins the SP10M’s get the barrels bonded. 620 is a bonding agent amongst other things.

 

[msgriff]

I couldn't imagine a hair dryer doing it. I'm not sure about a heat gun but probably not. Torch....Ehhhh if you're not careful maybe

I just want to understand how hot to get the end of the receiver for a thermal fit.

Something to keep in mind is that anodizing starts to "craze" at 350f. A lot of variables on how severe that crazing can be. It would also be subjective regarding the detrimental effects of your typical AR.

 

[PappyM3]

Something to keep in mind is that anodizing starts to "craze" at 350f. A lot of variables on how severe that crazing can be. It would also be subjective regarding the detrimental effects of your typical AR.

Good to know, and reinforces me using a heat gun.

 

[msgriff]

Good to know, and reinforces me using a heat gun.

Yup, a rapid change in temp is one of the variables that you should try to avoid.

 

[KCode]

Something to keep in mind is that anodizing starts to "craze" at 350f. A lot of variables on how severe that crazing can be. It would also be subjective regarding the detrimental effects of your typical AR.

I have no idea how hot a heat gun will get it but I would think just to the point of too hot to touch would be, what, 200f max?

 

[Kinked_Chrome]

I want to do a M5 enhanced next but I wonder about getting the shim installed right thru that interface. I thought though I’d just glue it with 620. I’ve never seen a m5 enhanced in person, maybe I’m overthinking it.

I shim and thermal fit both large and small frame enhanced upppers. Its more of a pain, but its doable. I always measure the bore dia and the extension dia though, so i dont have to guess and check for the shim stock thickness.

For people asking about how to heat. Ive used to do them in the oven and then check the temp with an infrared thermometer. Now i just use a propane torch.

 

[KCode]

I shim and thermal fit both large and small frame enhanced upppers. Its more of a pain, but its doable. I always measure the bore dia and the extension dia though, so i dont have to guess and check for the shim stock thickness.

For people asking about how to heat. Ive used to do them in the oven and then check the temp with an infrared thermometer. Now i just use a propane torch.

What infrared temp do you aim for?

 

[Gohring65]

I shim and thermal fit both large and small frame enhanced upppers. Its more of a pain, but its doable. I always measure the bore dia and the extension dia though, so i dont have to guess and check for the shim stock thickness.

For people asking about how to heat. Ive used to do them in the oven and then check the temp with an infrared thermometer. Now i just use a propane torch.

Good to know, that’s one of my main reserves on getting an enhanced upper. I’ll probably just go with one since it’s not impossible. Lol

 

[Kinked_Chrome]

What infrared temp do you aim for?

Id have to do the math again, but my memory is telling me a deltaT of 200F gave a increase in dia of .004. Just google up the expansion coefficient of Al and the equation for expansion of a pipe and itll give you a good estimate. Aim for .004 to .005in for your barrel to slide in easy. I wouldnt heat the upper more than 350F though.

 

[DHDeal]

What a good thread. Seems that most posts are for bedding (however you choose to go about it) than against.

I saw where using loctite bedding helped an AR that strung shots vertically at least 10 years back. It used very good parts but strung shots badly (Mega upper/lower and a Krieger barrel). We used Loctite and let it set up and there it was. Since then I've bought rolls of SS stock from McMaster-Carr (.001" and .0015") and used it instead of Loctite. Preferably I'll buy a heavy upper that is interference fit but those are only available in certain configurations. I'm not a fan of M4 style uppers for a couple reasons for my toys so that leaves me few choices in a tight fit heavy upper. The last 3 I've bought have all been Iron City Hatchet uppers and I really like them and they have all helped create very good shooting rifles. Nordic Components also makes a good heavy walled upper but they are as plain as a paper plate....

I pulled apart an upper I had previously bedded using Loctite and the Loctite was smooth as glass and still blue where it was thick enough to see the color. It works well but I still prefer an upper that has to be heated up to make the extension fit regardless of whether I shim stock or not.

Since I try to make the whole package as strong and tight as possible, I will also use a forearm with as long of a nut as available. I have Seekins SP3R, Geissele Mk14, and Lantac rails and they all have made for very good shooting rifles.

The last piece of the puzzle for me besides always using very good quality barrels, is either a Young Manufacturing NM or JP carrier. I have read all of Joe Carlos' articles and his advice works for me. I've gotten spoiled building AR's this way. I'll do a few other tricks while I build an upper but those are mainly to keep brass from getting gouged up on their way out of the chamber. Like most that have posted here, I have a certain way I build all my rifles but will always listen to good advice.

 

[RickyRodney]

I have been following this thread, and the similar threads in the past. I opted to pick up a aero enhanced upper and I have some seekins parts waiting on builds. My current barrel slides right into the aero upper and has a small amount of detectable wobble in the upper. Now I have to decide if it worth trying to shim/ bed with 620 the recessed extension and gain the reduction in handguard deflection VS just buying a thermofit BCM upper?

What would the hide do?

 

[Gohring65]

I have been following this thread, and the similar threads in the past. I opted to pick up a aero enhanced upper and I have some seekins parts waiting on builds. My current barrel slides right into the aero upper and has a small amount of detectable wobble in the upper. Now I have to decide if it worth trying to shim/ bed with 620 the recessed extension and gain the reduction in handguard deflection VS just buying a thermofit BCM upper?

What would the hide do?

After discovering bedding and shimming I don’t let a loose fitting upper go to waste. I shim and bed them and use them, this process basically fixes them so why not. But I get it if you want a better fitting upper for maybe a one and done precision project.

 

[KCode]

I have been following this thread, and the similar threads in the past. I opted to pick up a aero enhanced upper and I have some seekins parts waiting on builds. My current barrel slides right into the aero upper and has a small amount of detectable wobble in the upper. Now I have to decide if it worth trying to shim/ bed with 620 the recessed extension and gain the reduction in handguard deflection VS just buying a thermofit BCM upper?

What would the hide do?

If it were me I would try and send it back to see if another one was tighter. If I didn't have to deal with a lose fit I wouldn't.

 

[DHDeal]

I have been following this thread, and the similar threads in the past. I opted to pick up a aero enhanced upper and I have some seekins parts waiting on builds. My current barrel slides right into the aero upper and has a small amount of detectable wobble in the upper. Now I have to decide if it worth trying to shim/ bed with 620 the recessed extension and gain the reduction in handguard deflection VS just buying a thermofit BCM upper?

What would the hide do?

I've shimmed probably half a dozen of the Aero M4E1 uppers (not the ones with the rail interface). Usually the .0015" SS shim stock work best with them. Like I stated in my earlier post, I will always shim instead of Loctite when fitting a barrel. Yes, the BCM will work well too, but that would be $100+ compared to a few dollars for shim stock for the upper you already have. That said, Loctite does fill every space in the extension/upper.

 

[RickyRodney]

thanks guys im going to try to glue on a shim and stuff it in the enhanced upper, wish me luck.

 

[WindstormSCR]

Yes, and this entire issue is also why my 6ARC I'm working on will be using the Athena chassis (drake associates, but they licensed it to springfield who sold it as the "edge atc" )

I'll probably go the extra step of getting a slightly oversize barrel extension and turning it down to the desired interference fit myself, before thermal interference fitting it.

other considerations for the build will be an anti-tilt carrier (I've done the screw mod to a BCG, I'd rather have a factory made one), and a careful selection of buffer tube with a captured spring to keep everything nicely in line and consistent.

 

[LRRPF52]

LOL. Yea, that works out well too. Randy Selby "The Real Gunsmith" is a fine example of just relying on age and "experience." It doesn't take a 40yr old to become an SME.

Also, that "kid" in the video is either in his 40's or very close to it, and has been a gunsmith for 15 years or so. He guest instructs at several gunsmithing schools around the country.

And yes, I'm well into my 40's.

One of the only younger guys who really impresses me (and older precision rifle smiths I know) so far is Ultimate Reloader.

In the case of bedding AR-15 barrels, Caleb is just on the wrong side of the facts.

The whole reason I got turned onto the bedding technique was from Bill Alexander, who also looked at what the AMU had done with it. Bill said when he was doing fleet Grendel accuracy testing with 10 different rifles, all using the exact same components, high-end cut-rifled pipes, billet receivers, free-floated, same torque specs, trick triggers, high-end optics and mounts, 5 of the rifles would shoot no matter what you did, and the other 5 didn't.

He applied the AMU bedding approaches, and bedded the gas blocks too, then the rifles tightened up demonstrably. AMU used much higher sample sizes across large fleets of uppers for the team, and started making waves when they consistently out-shot the USMC Rifle Team.

I first tried it on a JP 18” .223 Wylde barrel I had in a generic M4 upper. It was shooting 5rd groups into 1.7” at 100, which is just not what I expected that barrel to do. The barrel was given to me and had a high round count on it already, so I figured I’d at least see if bedding would change anything.

I trued up the face of the upper, which was way out of square, then bedded the barrel.

Took it out again and I’ll be if it didn’t shoot .5 - .6 strings of 5rds.

Another notable rifle was an Iron Ridge Arms AR-10 billet set build with a Krieger 20” pipe. It had a DPMS aluminum gas block that was gas eroded out, had a standard RLGS tube with an ArmaLite gas position, and was shooting 1.5-1.7” groups at 100 with a known Sierra hand load that shot lights-out in other rifles.

I stripped it all down, got a new steel gas block for it, ArmaLite gas tube, and bedded the barrel into the IRA upper. Took it out and started zinging .6” groups with that same load.

The JP example, AMU testing, and Bill A.’s recommendations made me a believer, and the Krieger pipe in IRA billet set just confirmed it. When GAP built my different custom LR-308 and LR-260, I think they did similar accurizing techniques as well. Both are freaking lasers, always have been from the first groups to the last. One was an Obermeyer pipe, the other a Bartlein.

I also did some single variable testing with this with 22” Lilja bull barrel 6.5 Grendels in Seekins billet receiver and their handguards. No bedding: 1.2” 5rd groups. Bedded: .3” to .4” rapid-fired 5rd groups with factory 123gr Hornady A-MAX.

I just bed my barrels as a rule and have done so for about 13 years now. Everything has been MOA or better, usually in the .4 to 1 mil region with quality factory ammo. Even the little 12” Faxon 6.5 Grendel shoots MOA or under with most factory loads.

Bill A. also mentioned something about gas system input onto the barrel with the port acting like a jet, 90˚ off-axis from the bore. It was more pronounced with external piston guns if I recall. He used to offer Adams Arms piston Grendels back in the day.

I also had this conversation with John Paul, owner of JP Enterprise. He said from a manufacturing standpoint, it’s always hard to get consistent surface dimensions from anodizers, so even with perfectly-true machining on the upper faces, when you get them from anodizing, there can be a slant on the face, so it added cost and complexity dealing with it from that end.

He prefers the thermal-fit process if I recall, which they control with their extension tunnel ID and extension ODs in the parts feed into the builds.

Everyone can do whatever they want, but I know what I’m doing every time I put an upper together. For those that are trying to milk accuracy out of a trash, bottom-end barrel, I would advise to consider stepping up a price point or 2 and get something a little better before polishing a turd. Don’t expect miracles from some of the lower-end tent stakes floating around out there.

 

[LRRPF52]

LOL. Yea, that works out well too. Randy Selby "The Real Gunsmith" is a fine example of just relying on age and "experience." It doesn't take a 40yr old to become an SME.

Also, that "kid" in the video is either in his 40's or very close to it, and has been a gunsmith for 15 years or so. He guest instructs at several gunsmithing schools around the country.

And yes, I'm well into my 40's.

After 20 years of pretty intense study and regular hands-on experience with AR-15s, M16s, and M4s, I thought I knew most of what there was to know about the design and its history, assembly, function, and troubleshooting. I could name every part from memory, assemble, do some general fixing, and seemed highly-competent to myself and those with less experience.

The me today would tell that me, “You don’t know jack or squat about this, but if you stay hungry and don’t stop learning, you’ll be so much farther ahead in another 20 years."

When I approach an AR-15 build now, it doesn’t even feel like I’m working on the same design. It feels like literally different lifetimes between that me and me now.

One main thing that’s different, besides all the tools and techniques I’ve acquired along the way, are the availability of parts I personally have on-hand. I keep as many uppers and barrels around, so when I go to assemble once the barrel specs have met what I’m looking for, I can closely match the OD of the extension to the ID of the tunnel in the upper by checking several different uppers.

I don’t have to be pigeonholed into one upper that I ordered, so that starts off the tight fitment however I want. The tightest one I ever did took me at least 45 minutes to get the extension seated in the upper. That was a 12” Grendel pipe in a 2A Armament Balios Lite upper. It shot great right out the gate with 123gr ELD-M, 5rd groups into .75 to .9 MOA, which is hard to do with a lightweight build pushing that projectile weight.

There is a whole different world in the material science and processes side of things with the AR-15 that is the separator between serious manufacturing and amateur assembly. I try to take it as serious as an aerospace project, since the materials and components that are core to the AR-10 and AR-15 came from Stoner’s experiences in the aerospace sector. Aircraft aluminum (receivers) and hydraulic lines (gas tube). It’s a genius design that nobody has been able to best when looking at weight, balance, accuracy, and reliability for self-loaders.

Much of the industry is actually going backwards in time away from it, not forwards.

 

[Tx_Aggie]

One of the only younger guys who really impresses me (and older precision rifle smiths I know) so far is Ultimate Reloader.

In the case of bedding AR-15 barrels, Caleb is just on the wrong side of the facts.

The whole reason I got turned onto the bedding technique was from Bill Alexander, who also looked at what the AMU had done with it. Bill said when he was doing fleet Grendel accuracy testing with 10 different rifles, all using the exact same components, high-end cut-rifled pipes, billet receivers, free-floated, same torque specs, trick triggers, high-end optics and mounts, 5 of the rifles would shoot no matter what you did, and the other 5 didn't.

He applied the AMU bedding approaches, and bedded the gas blocks too, then the rifles tightened up demonstrably. AMU used much higher sample sizes across large fleets of uppers for the team, and started making waves when they consistently out-shot the USMC Rifle Team.

I first tried it on a JP 18” .223 Wylde barrel I had in a generic M4 upper. It was shooting 5rd groups into 1.7” at 100, which is just not what I expected that barrel to do. The barrel was given to me and had a high round count on it already, so I figured I’d at least see if bedding would change anything.

I trued up the face of the upper, which was way out of square, then bedded the barrel.

Took it out again and I’ll be if it didn’t shoot .5 - .6 strings of 5rds.

Another notable rifle was an Iron Ridge Arms AR-10 billet set build with a Krieger 20” pipe. It had a DPMS aluminum gas block that was gas eroded out, had a standard RLGS tube with an ArmaLite gas position, and was shooting 1.5-1.7” groups at 100 with a known Sierra hand load that shot lights-out in other rifles.

I stripped it all down, got a new steel gas block for it, ArmaLite gas tube, and bedded the barrel into the IRA upper. Took it out and started zinging .6” groups with that same load.

The JP example, AMU testing, and Bill A.’s recommendations made me a believer, and the Krieger pipe in IRA billet set just confirmed it. When GAP built my different custom LR-308 and LR-260, I think they did similar accurizing techniques as well. Both are freaking lasers, always have been from the first groups to the last. One was an Obermeyer pipe, the other a Bartlein.

I also did some single variable testing with this with 22” Lilja bull barrel 6.5 Grendels in Seekins billet receiver and their handguards. No bedding: 1.2” 5rd groups. Bedded: .3” to .4” rapid-fired 5rd groups with factory 123gr Hornady A-MAX.

I just bed my barrels as a rule and have done so for about 13 years now. Everything has been MOA or better, usually in the .4 to 1 mil region with quality factory ammo. Even the little 12” Faxon 6.5 Grendel shoots MOA or under with most factory loads.

Bill A. also mentioned something about gas system input onto the barrel with the port acting like a jet, 90˚ off-axis from the bore. It was more pronounced with external piston guns if I recall. He used to offer Adams Arms piston Grendels back in the day.

I also had this conversation with John Paul, owner of JP Enterprise. He said from a manufacturing standpoint, it’s always hard to get consistent surface dimensions from anodizers, so even with perfectly-true machining on the upper faces, when you get them from anodizing, there can be a slant on the face, so it added cost and complexity dealing with it from that end.

He prefers the thermal-fit process if I recall, which they control with their extension tunnel ID and extension ODs in the parts feed into the builds.

Everyone can do whatever they want, but I know what I’m doing every time I put an upper together. For those that are trying to milk accuracy out of a trash, bottom-end barrel, I would advise to consider stepping up a price point or 2 and get something a little better before polishing a turd. Don’t expect miracles from some of the lower-end tent stakes floating around out there.

I've owned rifles built by AA back when Bill still owned the place. They were absolute tack drivers, and just like you say, the uppers were completely glued together.

Those were the first rifles I'd ever seen with a gas block bedded to the barrel, and it surprised me at the time. Now, having seen first hand how something like a misaligned gas tube can ruin the accuracy of a DI gun, I can see why Bill would choose to bed the gas block.

His old G10 handguards were also great: simple, stiff, and thermally neutral.

 

[LRRPF52]

I've owned rifles built by AA back when Bill still owned the place. They were absolute tack drivers, and just like you say, the uppers were completely glued together.

Those were the first rifles I'd ever seen with a gas block bedded to the barrel, and it surprised me at the time. Now, having seen first hand how something like a misaligned gas tube can ruin the accuracy of a DI gun, I can see why Bill would choose to bed the gas block.

His old G10 handguards were also great: simple, stiff, and thermally neutral.

As the industry moved more into slimmer and Keymod, then MLOK aluminum handguards, dudes looking to conform with trends scoffed at the AA handguards. I saw a guy tell Bill A. to his face at SHOT once, “I like your rifles, but your handguards are sh*t.” Bill remained very cordial, didn’t argue with the guy.

Looking at everything now, those cut-rifled GDRMs and GSRs are collector’s items. They just shot. If you went with the lower price-point rifles, you weren’t going to see that kind of precision and consistency, but they still were good.

The first person who made me aware of 6.5 Grendel was an instructor at SOTIC/SFARTAETC at Bragg in 2003. He was an early adopter, bought the best 24” AA Grendel he could get out of the gate. The guy had to bring in an assessor to count his safes and rifles for insurance purposes, and was a long-time long-gunner from CIF out of Okinawa, then at the School House. He said that rifle was the most accurate rifle he owned. He wasn’t prone to hype, more of a low-key, softer-spoken guy, so it didn’t make any sense what he was saying because he had a lot of laser bolt guns. He loved that Grendel.

I waited at least 5 years for the bugs to get ironed out with what I always see as beta testers, then I ordered a barrel/bolt combo from Midway in 2009. In hindsight, I wish I had bought one of the full-up billet Mega monolithic upper GDMRs or GSRs with a cut-rifled Satern pipe when they were available.

I Cerakoted a 20” one for a friend with the G10 handguard. I didn’t want to let it go back to him.

 

[Makinchips208]

Anodizing has been brought up several times as a possible cause of receiver faces being not true or flat.
In my journeys I have measured new AR upper receiver faces several thousandths off from perpendicular to the receiver bore, some were not even very flat either.
However, anodizing would not cause this condition. If a receiver face is not true then it is almost always manufactured that way, or another process messed it up. Such as material was removed during deburing, sanding, sand blasting, or tumbling. Or one of these processes left grease or contamination in/on a part of the face etc. this can effect the anodizing process negatively. Many things can go wrong, and it takes effort to get it right. Often the blame gets pointed at anodizing though.
Having made many thousands of parts, and hundreds of different types of parts, sometimes problems have arose. Spending time in the anodizing shop with the owner and operator I learned a lot and how I could make better parts, and learned that anodizing was literally never our problem. If done properly, Anodizing thickness or dimensional change within a single part is extremely uniform and so small that it is completely irrelevant, in the case of ar receiver faces.
I’ll link a pdf that is very informative and well written as one reference.

https://www.alphametal.com/images/stories/alphametal/UnderstandingSpecifyingAnodizingOsborn.pdf

The knowledge, skill, and expertise of weapon building and assembly here is exponentially greater than mine, by far! But the little bit of ar building I have done points to “truing may help, but bedding certainly helps. And nothing fixes a junk barrel.”