Loctite 609 Retaining Compound on Barrel Sleeve? What do y'all use on barrel sleeve?

[M4Fundi]

I have seen a couple of places where Criterion Barrels recommends you clean your receiver and barrel sleeve to dry with a degreaser, then heat receiver threads with a torch for several minutes and then apply Loctite 609 Retaining Compound to the barrel sleeve liberally and insert and let cool. The thought being that the Retaining Compound expands and hardens on fast and you never get any barrel shift, etc.

Is this common and I have missed this all these years or is this a Criterion thing?

What does everyone else use on barrel sleeve for your builds? Anti-seaze? Lube? Dry? Retaining Compound with or without heat? What?

[One More Time]

Not sure what heating it is supposed to do.
It doesn't need heat to cure.

I use 609 and 620 at work all the time.
620 is for high heat applications.
If you really want it to set just clean and use the activator with it.

I just use moly lube on the barrel.
After messing with stuff that's been glued in properly with 609/620 I would think the upper would be a consumable if used.

[556Cliff]

This practice is a long range shooting competition thing. They've used shims, Loctite retaining compound, oversized dimeter barrel extensions and now the more popular method is thermo fitted upper receivers (as available through BCM and a couple other places).

It's all kinda pointless unless you are one of the competitors in those long range shooting competitions. And even then I wonder how much difference it really makes or if it's more of a placebo effect.

Colt doesn't do this and most other manufacturers don't either and there have been a lot of really accurate rifles out there despite not being assembled with green goo, shims and overly tight barrel extension to receiver fit.

I assemble my barrel extensions into the receiver degreased and dry. Oil soaks in and around the extension after being assembled.

[ViniVidivici]

I used red loctite on the last build, just to give it a try. Never done it before on others.

The gun IS accurate, but I have no scientific way of determining if the bedding made it more so than it would have been without it.

[JediGuy]

I shimmed on a gun I specifically built for precision, and I recently used 609 or 620 (I don’t remember which) on a 13.9 Criterion barrel that I use for general purpose. I don’t know if it helped the mechanical accuracy or not, but I don’t see an objective way that it could hurt. Same with squaring/truing the face of the upper receiver.

[556Cliff]

I shimmed on a gun I specifically built for precision, and I recently used 609 or 620 (I don’t remember which) on a 13.9 Criterion barrel that I use for general purpose. I don’t know if it helped the mechanical accuracy or not, but I don’t see an objective way that it could hurt. Same with squaring/truing the face of the upper receiver.

And that's really the main argument that I see in support of bedding and truing the receiver face. "It can't hurt, so why not do it?"

I'm not saying people shouldn't do it, but personally I'd love to see some testing done to see what kind of difference (if any) that it really makes. There are situations and certain set ups where any gain in accuracy might make some difference. And that's with long range competition rifles and rifles geared more towards precision. Everything else which probably falls into the 99% it just doesn't matter because they are not going to be used in that extreme and most shooters aren't good enough to take advantage of it.

[JediGuy]

Let’s say it can improve .25 MOA…couple that with a nice, light trigger, and it matters cumulatively. Others have provided objective data, so if it could potentially maximize the performance of an average shooter…it’s worth it.

[M4Fundi]

I was taught by a USMC armorer to use Aeroshell MS33 military anti-seize on the barrel sleeve so you never have to worry about not being able to pull the barrel for the next change. Thoughts?

The heat I was referring to is what Criterion does for ease of insertion I think for their very tight barrel sleeve tolerances. Not sure if it helps set the Loctite 609.

[556Cliff]

I was taught by a USMC armorer to use Aeroshell MS33 military anti-seize on the barrel sleeve so you never have to worry about not being able to pull the barrel for the next change. Thoughts?

With the typical slip fit of normal (Colt spec) parts I can't see any point in doing that. Oil will seep between the barrel extension and the barrel extension socket of the upper. On assembly what you don't want is lube between the rear facing side of the barrel extension flange and the contacting socket face of the upper. The more friction there the better so that the surfaces are less likely to slide on each other while applying torque to the barrel nut. However, you do need to liberally apply grease to the front facing side of the barrel extension flange that contacts the clamping surface of the barrel nut to reduce friction as much as possible so it doesn't drag and seize up.

And YES to the liberal application of grease on the threads of the upper.


On a thermal fit upper I might oil the external surface of the barrel extension and blow it off with the air compressor before putting it in the upper, but no grease.

[Stopsign32v]

620

not 609