bedding the barrel

[snell]

Lately I've hears several folks of extensive experience recommend "bedding" the barrel of the AR platform using Loctite. Has anyone here had any experience with doing this and if so what are the pitfalls?

[ricsmall]

The majority here do it. I’ve never seen any pitfalls, easy to get out I need be.

[A5BLASTER]

Quick search on this fourm with the search feature would have brought up more threads on this subject then you could read in 2 days.

No pitfalls all to doing it, simple and effective, some think it's not necessary others think it makes a diffrence.

Me I'm doing everything I can too get all the accuracy out of my setup I can. Lapp the reciver face, bed the barrel, bed the gas tube in the gas block, bed the gas block, use balanced tourqe technique on barrel nut, gas block and muzzle device.

Top end trigger, top end scope mount good scopes, fixed buttstock and most importantly step up too a better barrel rack grade cheapest online just doest cut it in my book.

Follow these things are most of these things and the rest of the accuracy equation is on the ammo and the marksman.

[Klem]

I don't do it.

I tried it once and it made no difference to group sizes. To be fair the fit was pretty tight to start with (not an interference fit but no play).

If the fit was loosey goosey I would consider it, but probably source a tighter upper instead.

[Mesa1978]

I did it with a leftover DPMS slab upper and a Stoner 16" .300 Blackout, since the fit was loose. Lapped, bedded with Blue 243 and used aeroshell for the nut. I don't know if it really makes a difference, but I can consistently get MOA groups suppressed with 190 sub-sonic Hornady, so I'll take it.

I've lapped the Grendels, but really didn't need to bed, because of the fit, windage is very centered on my builds, the purchased complete uppers; not so much.

[R2BRO]

just stumbled on this post, i never thought about connection between accuracy and how tight the barrel fits into upper. I remember in my current build (which ha BCA barrel which ill change to Faxxon) when i was installing the barrel i just put that in and thats it. I did not have to sweat on trying to push it inside. is that a problem then?

but then how do you define tight? :p

for example in this picture below:


At the current state of that picture, i can still rotate the barrel inside. and if i try moving it...then i can feel very very tiny play....does it mean its loose??

couple more questions:
1) i'm planning to use that regular gun grease for that barrel, is this what you all use?
2) any links/suggestions to quality upper with tight specs but which does NOT have forward assist?

thanks/

[R2BRO]

even if i fully seat it inside, and try to move along the axis perpendicular to barrel, i still can feel very light but tiny play... so.. no go then? or any suggestions?

the thing is - the moment i screw in barrel nut with hands without even tightening it with wrench, that loose play goes away... so what can you tell then?

[BCHunter]

even if i fully seat it inside, and try to move along the axis perpendicular to barrel, i still can feel very light but tiny play... so.. no go then? or any suggestions?

the thing is - the moment i screw in barrel nut with hands without even tightening it with wrench, that loose play goes away... so what can you tell then?

Yes this is a loose fit, and bedding should help. A tight fit means thermo fitting you have to freeze the barrel and heat the upper,to get it to slide in. BCM and Jp uppers I've seen mentioned the most requiring thermal fitting. Dont know if a faxon barrel justifies that expensive of an upper?

[BCHunter]

Use wheelbearing grease with moly on the barrel nut.

[A5BLASTER]

just stumbled on this post, i never thought about connection between accuracy and how tight the barrel fits into upper. I remember in my current build (which ha BCA barrel which ill change to Faxxon) when i was installing the barrel i just put that in and thats it. I did not have to sweat on trying to push it inside. is that a problem then?

but then how do you define tight? :p

for example in this picture below:


At the current state of that picture, i can still rotate the barrel inside. and if i try moving it...then i can feel very very tiny play....does it mean its loose??

couple more questions:
1) i'm planning to use that regular gun grease for that barrel, is this what you all use?
2) any links/suggestions to quality upper with tight specs but which does NOT have forward assist?

thanks/

Me I would lapp the reciver face, break out the steel shim stock I have, find the thinnest quages I have that keeps me from installing the barrel.

Put barrel in freezer and bout a hour later heat upper with a temp gun, get it good and warm so it expands, instal the barrel and let both cool to room temp.

Then drop a small dab of good old cheap mobil one barring grease from the local auto shop, install barrel too property tourgue and go enjoy my rifle.

[R2BRO]

BCHUnter:

Will something like this work?
https://shop.advanceautoparts.com/p/valv...lsrc=aw.ds

A5BLASTER:

Sorry I need to clarify the procedure since I didn't quite get it.

1. lapp the receiver face, what you mean by face? internal walls of upper which get in close contact with barrel when it enters upper? And if yes, how do you "lapp" it?

2. break out the steel shim stock --> not getting it, what is that procedure doing?

3. which thinnest guages, ?

4. last part about putting barrel in freezer and heating the upper then fitting i understood well, however; couple questions, first, where do i drop that barring grease to? on interconnect line between barrel and upper or?
i want to ask if i need to take it out again after it expanded and cooled down, and then lube it with grease (or with above mentioned grease?) and put back on?
In other words - after thermal expansion fitting, do i need to remove it, grease it, and put back on before doing final torquing?

[R2BRO]

alright i guess i'll have to do some more work on researching it, i see already different materials online, so i'll come back

[BCHunter]

Yes that will work, it has the moly and a high temperature range.
The lapping is on the front face of the upper, top of the threads, you need a lapping tool and lapping compound from midway or brownells. The grease goes on the threads of the upper, so the barrel nut doesn't seize up over time and use.
Since you have a little play between your upper and barrel spread blue loctite on the barrel extension, make sure to clean any excess off inside the upper let set with barrel nut hand tight then step torque the barrel nut down 3 times to prevent gaulding of the threads.

[R2BRO]

few questions BCHunter:

1) why blue loctite? isnt the red one which is for high temp?

2) so...i freeze barrel, then heat the upper, then put loctite on frozen barrel extension before fitting? just trying to clarify it and sync with other actions.

[BCHunter]

Red is permanent you may never get the barrel and upper apart again, blue is removable if you ever need to change the barrel out.
The freeze heat method is only necessary on tight uppers, and generally dont need the loctite. Because it is so tight. If you can slide your barrel in and out at room temperature then bedding is believed to help take the play out.

[R2BRO]

got it!