If a barrel is sloppy in the upper, it's a crap shoot as to how close to centered it will be. This impacts a lot of things, including sight offsets.  Of course if I got a barrel that was sloppy in an upper, I'd measure both upper and barrel, and if both were new, whichever one was farther out of spec would be returned.  

A 15% difference in one test would be good data.  It would indicate the need to do an actual experimental evaluation of whether that bedding process worked or not.  Not that I think the Internet Guy wasn't telling the honest truth, but there's no way to tell if the result was just because of his bedding.  And there's no way for him to have completely avoided a bias toward the bedded shooting by doing his part just a bit better.

To do this experiment right, you need two uppers and two barrels.  Assemble both with the closest attention to perfect fitting as possible, except one would be bedded with Loctite 620 and the other not.

Now have a good marksman shoot both uppers using the same lot of high quality ammunition for the best groups he can possibly get.  The key here is that the marksman CANNOT know which upper is which.

Now tear both uppers apart.  Reassemble the one that was bedded without the Loctite, and when the other is reassembled, bed it with the Loctite.  Have the same marksman repeat the shooting with the same lot of ammunition, and preferably under the same atmospheric conditions.  Again, the marksman cannot know anything about the two uppers.

I'd take copious measurements of both uppers and both barrels before any assembly was done, and collect group size data for each condition.  Once all the shooting was done, correlate group size to bedding (yes/no), AND to closeness of fit of each barrel when UNbedded.

My experimental hypothesis (the question this test would address) is that there would be only a very small difference in group size with each barrel between bedded and unbedded groups, assuming all other conditions were controlled for.  I do NOT know which direction that difference would go - to the bedded condition or the unbedded condition.  That would be a different hypothesis.

But hey, I LIKE experiments.  I like them because they will tell you one of three things: the experimental hypothesis was right, the hypothesis was wrong, or the results aren't conclusive - but that tells you what your next hypothesis should be.  Experiments generate facts, not opinion, and certainly not "it feels like this helped" results.

Considering that I am not a gnat neutering shooter, I don't feel that the potential improvement in accuracy with a good quality barrel and upper is worth the experimental time and cost for me personally.

To all of those that have offered solid advice or even tried, I say thanks.
It will be my first A10 build and I'm gonna try all the lil tips and tricks posted here and in other areas ( hellbenders).
A lot of it I was already doing but the muzzle device was a new one.

To all of those saying fuck it waste of time, have a drink and try something new.

Can you say who the two manufacturers are?

 

Which one?  I've seen this once before, and just read again on that link you posted (not putting too much torque on the muzzle device)

Obviously you don't want 'spec' for a flash hider which is around 15-20...and I've seen some suggest as high as 30.

What would be a 'minimum'?  How well does that Rocksett hold?  And which number Rocksett?

EDIT: Never mind....I think their different #'s refer to the size of the bottle, not the formula of the Rocksett.

I did not account for this.

Team work! Ha!

Take out the human element

I have experienced this on my last few SilencerCo ASR brake installs.

Fudd gun and fudd gun holder.

Hmmm, might need to learn to bend tubing also.

I think I will use blue on my 16" AA barrel when I assemble. Never done it, why not, can't hurt to try it. I measured and it appears I have .001-2 play, small amount of "wiggle" without barrel nut torque. After some reading, I see that this method helps centering the extension when torquing. I do understand that if heat, movement, etc. is happening, that will affect accuracy as shot to shot won't be consistent, which is what we want.

Barrels bedded with Blue Loc tite are easy to remove.

They just tap out with the upper receiver insert that looks like a long "T".

I'm not really visualizing this very well. I wonder if using a "reaction rod" type tool would hurt the chamber at all.

Nothing more than tapping out a shaft(ext) from a sleeve(upper) Delrin, wood, anything non marring or able to damage the extension or receiver.

One I disassemble that was bedded with blue was a PITA to remove, barrel was from the company that cannot be named which had a chamber that was improperly reamed.  Tried tapping out with a derlin rod and it didn't budge, heated it till was smoking and had to really hammer the crap out of it to finally free it.  From this I gathered that they don't always just tap out easily as been stated and expect to beat the shit out it.  At least that was my experience with a sampling on one.

.

Noveske Rifleworks is a pretty reputable. Many gunsmiths refuse to work on their factory built rifles because the glue everything together. Know this going into it, once you use these bonding agents you will play hell getting it apart.

My uppers from White Oak Armament (John Holliger) and Compass Lake (Frank White) have no "bedding" between the ext and receiver. Both are well known smiths and both uppers shoot very well in highpower matches.

That's cool.
So what bedding compound do you use ?

I went ahead and used Blue loctite on this one yesterday:





Aero upper and lower




 

That is nice.
I have that same barrel and jp high pressure bolt from Fulton.
Put it together to test function, then tore it down for some cerakote and custom brake.
Can't wait to get it back and put together.
I'm gonna lap upper and bed as well.

Post groups when you get time please.

I use Loctite 620 with great results but I haven't had to remove a barrel yet so I can't tell you how hard it would be.

https://www.youtube.com/watch?v=8Y1RsKKjDLU

So you're a cubs fan, cool.

This is one of the things I learned to compensate for on both muzzle brakes AND barrel nuts.   I use high quality PTFE tape as a thread filler on barrel nuts.

 

How many of you realize that the clamping load exerted by the barrel nut against the barrel extension flange on an AR-10 with the nut torqued to 80 lb-ft (lubricated threads) is approximately 18,000 lbs.  That is nearly 9 tons of force locking the barrel onto the receiver.  Believe me, the extension is not going to move in the receiver unless you are using the rifle as a sledgehammer.  Certainly not under normal use.  Bedding the extension in the receiver is not going to buy you anything except a PITA to remove the barrel later.

Huh? I guess you lost me. You had to compensate for thread locker (and timing) on barrel nuts? and now you use PTFE tape...on barrel nuts? Please tell me more.

What if we are not torquing the barrel nut to the maximum recommended torque of 80 ft/lbs?

Sorry about that...it was in reference to a post above that one, I think.



What I mean was, that when it comes to final timing on muzzle breaks and certain barrel nuts, I have to compensate for "locking compounds"  or thread filling compounds when I am timing them to final torque and position.



 

That doesn't making people removing the anodize from the face of their receivers before chemically bonding barrels into place any less unnecessary.

Say's who ?

At 30 ft/lb, the clamping force is still extremely large (I don't have the figures handy).  The barrel nut stretches the aluminum of the upper, and it is the elasticity of the upper's metal that "pulls" the barrel nut - and thus the barrel's flange - with that amount of force.

As I've stated before, in this thread and elsewhere, once the barrel nut is tightened (even just past hand tight), the barrel isn't going anywhere.

It seems people are getting better accuracy using these techniques. Can you explain why that may be?

It seems people were being cured of disease by having leeches remove their bad blood.  Can you explain why that may be?


Hint

[Deleted]

It's spurious.

I have a good friend that is a world class rifle smith building precision rifles that win competitions regularly.

He has told me multiple times that a lot of the work done on custom rifles to true, adjust, and tweak certain components is not really all that useful compared to a perfect chamber/throat/headspace and a great barrel.  

I would tend to agree.

What you do with that barrel, how you install it, bed, whatever, plays a huge role in bringing out the accuracy potential.

My rule if thumb is, if your barrel fits in easily into the receiver, with minimal resistance, regardless of any slop is present, you should bed it if going for dead nuts precision.

Remember, accuracy and precision are different things.

The whole point of this forum is to learn from other people with more knowledge and experience

It's up to you to choose who to believe

Video from someone who knows something

Not sure why you insist on thinking that your belief is the right one.
My question was what compound , not what do you believe.
Free country and all , but this is a tech forum, and you're just talking to hear yourself talk.

If it makes you feel important or needed help yourself.
But just cause you believe something or someone taught you something, doesn't make it so, never has and never will.

Only thing from you in this thread is that you're a cubs fan and like cats.
Not a cat guy myself but thats cool.
I like the pic of your cat.

In three years of accuracy testing I saw no evidence that this is a sound practice.  Just like barrel break-in voodoo the data just does not exist.  Does it hurt?  Probably not.

People are reporting "better groups," without a rigorous testing regimen to verify that report.  There could be an improvement simply from the extra time and attention they put into installing the barrel when they "bed" it.  And any process that helps ensure the barrel is more centered in the upper will make iron sights dial in more easily.

I think most of the "I got much better groups" reports are spurious to say the least, though I don't think people are lying.  I think they never did any careful assessment of their uppers' precision before they bedded them, and/or they assume it works because of the numerous reports of "the top competitors" using this process so they just parrot what they've been told.  A blinded, pre/post accuracy test using expensive, quality barrels and a very accomplished marksman or a custom machine rest system would tell the tale for those barrels, and maybe indicate whether or not there was a potential for the process to improve the accuracy potential of a given barrel.

On the whole though, I firmly believe that a good quality barrel that fits well in a good quality upper will provide all the potential accuracy that barrel is capable of.  I've said before in this thread that I would send back a barrel that did not provide a snug fit in an in-spec upper.  I've never seen a barrel that was in any way "loose" in an upper, and I've never found enough play, even when the extension was perfectly lined up in the upper, to even get plumber's Teflon tape in the mix, so I'm really curious how so many people are reporting using various kinds of shims.  The last several uppers I've built had a VERY tight, almost interference fit between upper and barrel.  These were not anything special uppers and DD, CMMG, Voodoo, FN and KAK Industry barrels.  One (I think it was the FN barrel) I had to put grease on the extension AND worry it in a bit at a time to get it started.  

I also feel that there are a lot of people "truing" the faces of their uppers even if there is no evidence they're out of square, and then going beyond just making them square.  This can cause more problems than it corrects, including opening up the upper's bore.  If you use any abrasive on an upper lapping tool, there's a potential for it to get inside the upper.  If I were to consider lapping an upper, I'd start out with chalk on the tool and see if a couple of turns with chalk left blank spots on the face of the upper.  If it did, I'd use the very finest valve compound I could lay hands on, and to a few turns by hand then recheck.  Repeat until there are no more un-chalked spots, and it'd be done.

I simply don't think that there are ANY well documented cases of rigorously tested before/after cases with AR barrel "bedding," and there are certainly none that have been reported in detail (the way Molon details all the steps in his precision shooting tests).  I'm a scientist; show me the data, and show me that it's been repeated enough to validate the process, and I'll sign on.  Until then, it's snake oil.  That doesn't mean it's "bad," but it's not something I'll go to any trouble with myself.

FYI, Molon used to lap uppers before he started using billet uppers.

Most lapping tools are relieved so the area inside the upper won't be cut even if a little lapping compound gets inside. You should always be careful to avoid any compound getting inside the upper. If any does get inside I would recommend cleaning it out before proceeding any farther.

I respect Molon's approach, but I also know he's cautious and methodical; lapping enough to get a perfectly smooth upper face would take very little time, and I'm certain Molon monitored his progress very carefully.

I'm not dissing receiver lapping.  I'm saying that a lot of people do way too much, and maybe not too well because of all this talk about how it "improves accuracy," without even considering that maybe this receiver might need just a touch, and this one even less to make them perfectly square.

I know about three different lapping tools, and all of them have relief grooves (of different widths) between the centering pilot and the flange that is supposed to lap the upper.  But I also know how some people can go overboard with anything.  There are a lot of ways to goof this up, and since Wheeler's tool came out apparently designed to be used on a power drill, there is a statistical certainty that someone has goobered several uppers messing with that tool.  We are talking about a precision tool that needs to be used with a gentle hand being used by underinformed, enthusiastic builders without the knowledge of what to watch out for.

I can agree with this.
I will be lapping by hand using 600 grit, with receiver facing up.

Did you know that having your barrel blessed by a Catholic priest tightens up groups by 15%?

There's just as much evidence to demonstrate this as there is to show anything else suggested in this thread...

Why?

Sounds like you have first hand knowledge of Catholic priests blessing your barrel.
How old were ya ?

Don't laugh.  There was very nearly a company called "Crusader Arms" built around this very idea.

Like I said its up to you on who to believe

I choose to believe the guy whose been involved in a high level of competition for 20 years