barrel bedding

[dlraymond30]

i have an Aero upper and a Colt 11.5 that I am putting together that is sloppy as hell. it will fall right in and out of the upper. there is no tension holding the barrel extension to the upper so i was wondering what there is to use to bed the barrel to the upper other than loctite? I think i saw a guy on youtube use some brown substance in a brown squeez tube but that was a while ago and i can't find it now. What have you guys used and have you seen success?
also, since this is a short barrel im not worried too much about super duper precision but would like to see decent groupings... it is a colt barrel!!!

as always, i appreciate your guys opinions and info!

Darrin

[GH41]

i have an Aero upper and a Colt 11.5 that I am putting together that is sloppy as hell. it will fall right in and out of the upper. there is no tension holding the barrel extension to the upper so i was wondering what there is to use to bed the barrel to the upper other than loctite? I think i saw a guy on youtube use some brown substance in a brown squeez tube but that was a while ago and i can't find it now. What have you guys used and have you seen success?
also, since this is a short barrel im not worried too much about super duper precision but would like to see decent groupings... it is a colt barrel!!!

as always, i appreciate your guys opinions and info!

Darrin

What do you mean? "there is no tension holding the barrel extension to the upper" Are you not going to use a barrel nut? You are worrying about nothing. Put it together and shoot it.

[fedupflyer]

Glen Zideker, world class AR shooter, recommends bedding the barrel extension to the upper by using red loktite.

[GH41]

Glen Zideker, world class AR shooter, recommends bedding the barrel extension to the upper by using red loktite.

Who gives a crap what a world class AR shooter does to get a nut??? The OP is talking about mounting a so so Colt barrel on a cheap ass Aero receiver. Where do you guys come from???

[HeruMew]

Who gives a crap what a world class AR shooter does to get a nut??? The OP is talking about mounting a so so Colt barrel on a cheap ass Aero receiver. Where do you guys come from???

Preach, Brother GH41!

Hallelujah and AMEN.

Slide it in, nice and gentle. Then torque that sumb***h down to 40lbs. Do three cycles to get the stretch out.

Go fire the dang thing. If you insist on buying anything to put on the barrel, 3M Grease. But remember, it goes on the threads mostly...

[tehpwnag3]

The rifle isn't going to Camp Perry. Assemble it properly and don't give it a second thought.

[MegademiC]

Gotta say, this is the first I’ve heard of bedding an AR barrel.

That said, bcm uppers are reported to fit tighter. But I agree with theassemble to spec and forget.

What kind of groups do you expect with and without bedding? What’s the practical impact on your use?

[dlraymond30]

Thanks for the opinions guys. This is going to be a hard use/training class gun that will run at least half of the time suppressed. I'm not really worried about how loose the barrel is to the receiver... Just thought that since it isn't together yet and it would be cheap and easy to slather something on there to remove slop, why not do it? It's like running premium gas in your car... Not needed for basic function but COULD add to a slight bit of performance or in this case, accuracy...
Anyway, thanks again.

-Darrin

[tehpwnag3]

The barrel nut will squeeze the receiver tight to the barrel extension.

[HeruMew]

Thanks for the opinions guys. This is going to be a hard use/training class gun that will run at least half of the time suppressed. I'm not really worried about how loose the barrel is to the receiver... Just thought that since it isn't together yet and it would be cheap and easy to slather something on there to remove slop, why not do it? It's like running premium gas in your car... Not needed for basic function but COULD add to a slight bit of performance or in this case, accuracy...
Anyway, thanks again.

-Darrin

The biggest concern is that: if you're not popping rounds out to 800-900 yards, why? "Bedding", even though you can't really bed the barrel of an AR, would be more... Understandable? If that were the case.

If it's a usage rifle, use some grease around the extension and pop it on.

If it really is bugging you, get a BCM Blem upper for 74.99 and use the hair dryer to heat it up and put them together. The BCM is known to be a tighter fitting for the extension.

Nonetheless, you're worrying about something that's discernible. If you put Regular gas in a Ferrari, you will notice a difference.

In this particular example, it's not so mechanically the same as your analogy. You won't notice the difference for your classes.

Just trying to avoid your waste of cash, or hardships later if you wanna remove the barrel and it's loctited into place for no good reason.

Hope this makes sense and doesn't come off rude. We're just opinionated when people spend more time on tom foolery than just shooting the dang thing.

ETA: I should add. Bedding of most barrels happens on bolt action rifles to dampen or remove all barrel harmonics to avoid fluctuation.

The AR platform has been known to work best, in regards to barrel harmonics, when free floated as it removes a lot of the physical pressures that can impact barrel harmonics.

We're getting into deep, long range shooting concepts here. Long story short, unless you're mounting your AR into a full body stock in which you can cut cork and lay it out, your handguards will never give you grasp to "bed" the barrel to reduce harmonics.

YMMV, and I may be wrong. I have no real experience in it, and I am sure someone here does.

[26 Inf]

This earlier thread covers the issue, a quick read, especially if you skip through the usual bickering about whose pee pee of knowledge is bigger:

https://www.m4carbine.net/showthread.php?119904-Applying-loctite-to-increase-accuracy

tl:dr version:

pinzgauer: Bill Alexander has indicated in the past that while it is not *needed*, he has seen some benefit in using locktite on the barrel extension for grendels. It reduces some of the harmonics that can cause vertical stringing without having to over torque the barrel nut like some bench shooters do.

He was very clear that in any single rifle you may not see a benefit. Remember, grendels are normally sub-moa even with carbine rack grade barrels and half MOA is not uncommon with some care and decent ammo. So the grendel crowd is more accuracy oriented. Bill recommends Loctite 243, and it handles the heat in the receiver sections with no problem, yet can still be removed if needed.

For a typical hard use 5.56 carbine I personally do not believe you would see a benefit.

rob jensen: When assembling an AR for absolute accuracy (stainless barreled varmint, Hipower, 3gun) uppers I use Loctite between the bbl extension and receiver, between the gas block and bbl and on the threads of the muzzle device and use as little torque on the muzzle device as I can.

bp7178: I actually listed that answer in my first post in this thread, which was Loctite 609, and is a sleeve retainer compound.

Never had an issue removing a barrel if 609 was applied. You won't be pulling it out by hand though. Warm it with a heat gun and tap it out with a dowel.

pinzgauer: 243 is medium strength, can be unbolted even on very large bolts with hand tools. Hit it with localized heat (on the barrel you wore out) and it "unlocks". (actually, drops to about 20% of it's strength or less) Note: this is way more heat than you'd see in at the receiver in normal firing, even full auto.

As to who uses it, and the "trains of thought".... It would be a very broad generalization to believe that anyone who wants an M4C "tier 1 spec" carbines is therefore not concerned with accuracy. I want both if it does not compromise function or reliability.

I build my grendel carbines using DD, LMT & Colt components with the exception of the Barrel & Bolt, which I source from AA. (And Bill has mentioned they will be releasing a CHF barrel as well).

Grendels carbines can be very accurate, so it's worth using 243. I shoot SS "Gov profile" (M4 without 203 cuts) and have found them to be very accurate with several ammo combinations. The grendel (and I suspect 6.8) also puts stress on the AR-15 platform that 5.56 will never see. (Bolt thrust & barrel vibration)

Bill will also tell you that mil-spec receivers & barrel extensions can be sloppy by design due to tolerance stack, so they carefully manage extension to receiver fit to help with accuracy.

Not something the average 5.56 carbine user shooting cheap M-193 would ever see as an issue, but with inherent Grendel accuracy even with basic Hornady ammo it's worth making the effort.

I also see a trade off.... I'd probably worry less about the armorer changing barrels than a loose barrel nut stressing the gas tube and causing odd accuracy situation due to different barrel vibration/harmonics. Neither issue are common occurrences, but any armorer can change a 243'd barrel. Harder to deal with loose barrel nut issues away from the bench & tools. So for me it makes sense to err on the conservative side.

To be clear, I'm not advocating that M4C 5.56 shooters "glue", use random loctite, or even use 243.... just relaying what one very savy Mfg has shared which also aligns with other accuracy oriented mfg's & smiths indicate.

[HeruMew]

Great post 26.

Appreciate the insight. Good to have a broader perspective on the issue.

Still, as you mentioned, not worth the worry with it on a 5.56.

[dlraymond30]

thanks for finding that. I had issue finding any info on tightening up the receiver to barrel fit.

Darrin