Imagine how much you'd know if you tried some of this stuff for yourself.
Is bedding the AR barrel a myth? What's the best way?
- Thread starter KCode
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Not concerned about 620s gluing strength.
It's hard enough to remove as is. It takes an oak dowel and hammer hard on a concrete floor to remove.
The research & tech data is fine, but we don't need the parts glued permanently together....
Obviously you have never used 620 ...
As you say "it knocks out so easily"....it does not.
This is an 8.6 Blackout and the infamous 3 twist headed for the scrap yard.
I just had to try the 3 twist for my self.
Notice, the oak dowel is swaged up to get this barrel out. The dowel will be trimmed back for the next AR 10 barrel...and that's with the wax on the reciever only...which I tried to measure with a tenths indicator and got zero reading.
Plus there is only usually .0002" to .0005" maximum depth around the steel barrel extension to take up the tolerance and slight out of roundness between the 2 parts.
Why do some have good luck without doing the glue-ins because usually there is not that much extra space around the reciever and barrel extension ...but a few will "wobble" a bit.
And it makes improvements for me as one of the accuracy enhancements to the AR platform.
I actually measured the 620 thickness...here its about .0004" or 4 ten thousandths of an inch thick all the way across...but there are slightly thicker and thinner .0002" to .001" on one side as it drops into the groove...
So most of 620 sticks to the steel without activators, and expands to take up unneeded space to make a solid barrel to reciever fit.
The wax surface is non measurable.
We are not trying to glue them permanently together...just make a solid or nonmovable fit between the barrel and receiver.
It seems to work as most ARs assembled with 620 plus other accuracy enhancements will shoot quite few 1/2" groups with various powders and bullets.
An excellent example:
This is 9 mm with many thousands of rounds on it, with a binary trigger, so it got smokin hot more than a few a few times.
It also has tons of plus P loads in it almost exclusively...like 115 gr at 1720 fps.
The 620 buffs off easily with a fine silicon carbide deburring wheel.
Expensive? Cost per round in this case is ridiculously low, even if ya used it once and threw the rest away.
No one cares if ya use 620, use what ya like.
But I try to present the facts, through experience and actual measurement.
If I find something better, I'll use that.
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620 is $20 on Amazon and is enough to lay up hundreds of ARs.
620 kind of sucks and for none of the reasons you've said.
Loctite 620 on every AR barrel here with great success. I don't wax or do anything else, just 620 during assembly. Bonds very tight and easy enough to remove with the wooden dowel as has been described.
But I didn't say that, I was quoting someone else who said it knocks out easily with a wooden dowel.
We should be concerned about 620 final strength, but not in the context of "gluing" pieces together, we want the goop to resist movement, that's the goal. As I mentioned, reduced final cure strength does mean you are not getting the full potential of the 620, so then maybe I would choose a wax release and epoxy method instead?
I have used 620 on other things, the bottles usually have exp date on them about 1yr from purchase. Doing hundreds of AR's with 620 in 1yr? I applaud that effort.
For those who like using 620, use 620. I don't think is matters too much what goop is used, there's little diff between them in end results, but we know some Pros & Cons for each, and, we know using something is better than nothing at all. For me I found JB Red was just way easier to use.
The whole notion of "accuracy and precision" in the same talk as "should bedding be used" creates conflict. If I wanted to obtain the best accuracy and precision I would have the barrel maker provide barrel with oversized extension 1-3thou bigger than mic'd bore ID, then I would spin barrel and shave off what's needed to make that very snug fitment, and still use minimal goop stuff to lubricate the install.
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You're doing the same thing...trying to get a good fit and glue it in.
"Spin and shave off"...are terms that tell me ya don't have a clue.
You can buy oversized ground barrel extensions...but then ya have to torque them on an existing barrel, and the gas port probably won't line up.
Barrel extension metal is pretty hard.
Carbide will cut it at low speed.
I just threaded this old 8.6 Blkout barrel extension, 20 tpi, so one can thread the barrel into the reciever if he is a machinist, or handy with a lathe.
I'd start with Areo enhanced reciever with the heavy wall.
It has internal threads for the barrel nut.
That may have a potential to work out.
Or turn down the enhanced reciever and thread it. Then have a bushing with the internal and external threads to fit the reciever and the newly threaded barrel.
Thread the barrel in, check headspace. Or use a barrel nut like Savage to ease in barrel assembly and headspacing, feed ramps etc...last thing after everything fits is drill the gas port to line up...may have to mill a slot for the gas tube.
One can start from a barrel blank and do all the maching ...but this way it would be as solid as a bolt action that threads into the barrel.
And even mix AR 10 recievers and AR 15 recievers and barrels. Need a 2.8" COAL 223? Probably not...
Not very practical for the average guy.
But it might do it if I feel the need...
For now, I'll just probably do the same old 620 procedure for the most part, cause it works for me...
Til I feel something else is needed here.
"Spin and shave off"...are terms that tell me ya don't have a clue.
You can buy oversized ground barrel extensions...but then ya have to torque them on an existing barrel, and the gas port probably won't line up.
Barrel extension metal is pretty hard.
Carbide will cut it at low speed.
I just threaded this old 8.6 Blkout barrel extension, 20 tpi, so one can thread the barrel into the reciever if he is a machinist, or handy with a lathe.
I'd start with Areo enhanced reciever with the heavy wall.
It has internal threads for the barrel nut.
That may have a potential to work out.
Or turn down the enhanced reciever and thread it. Then have a bushing with the internal and external threads to fit the reciever and the newly threaded barrel.
Thread the barrel in, check headspace. Or use a barrel nut like Savage to ease in barrel assembly and headspacing, feed ramps etc...last thing after everything fits is drill the gas port to line up...may have to mill a slot for the gas tube.
One can start from a barrel blank and do all the maching ...but this way it would be as solid as a bolt action that threads into the barrel.
And even mix AR 10 recievers and AR 15 recievers and barrels. Need a 2.8" COAL 223? Probably not...
Not very practical for the average guy.
But it might do it if I feel the need...
For now, I'll just probably do the same old 620 procedure for the most part, cause it works for me...
Til I feel something else is needed here.
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I give everyone a bad time over "spun up a barrel" or "spin up" a barrel.
It's uneducated porn slang, gang cool, wannabee important, to sell your precieved intelligence on the subject of gun barrels, but instead it's instant explosion stupidity kind of statement...
I spent 35 yrs as a machinist, 5 yrs of apprenticeship, college, and later back to college to machine tool technology to learn programming.
Not "one" machinist, apprentice, or college instructor, shop owner, in many hundreds of encounters has ever used "spin up" referring to anything that you'd likely do with a lathe or mill and a long piece of round stock.
No apprentice or student would get by using "spin up" on the shop floor or in the class room...you would be harshly corrected.
To me it's just dumb ass gangbanger slang or afghan goat fuckers slang, letting your ego of cool talk, emphasize your own stupidity.
It's found on gun sites as a manly, testosterone, chest bumping, cool thing to say,...but it projects the mighty stench ignorance....like a rotting corpse.
Be that guy, and you shutter the window.
What phrase would you prefer people to use? Im sure some folks use “spin up” etc to sound cool but others probably just dont feel like typing out chamber, chop, and crown every time
Too many "smart" people either don't get this or they simply don't understand the concept & try to overthink it.
By far, the easiest method is to use a thermofit upper, like BCM, SanTan, or Cross Machine...............if one of those can't satisfy you, then 620 is your friend. IMHO, SanTan & Cross leave little to be desired.
It's really just that simple.
MM
"Chamber," is a good start ...then ya know what's being done...one word.What phrase would you prefer people to use? Im sure some folks use “spin up” etc to sound cool but others probably just dont feel like typing out chamber, chop, and crown every time
"Spin up" is two words, ...that only dipshits on gun sites use to try to impress their dumbass dipshit buddies, who conjure up false visions grandeur, by saying it.
When I see it...It's like putting up a giant neon sign over your head, telling the whole world what a dumbass dipshit you really are...uneducated in machining, , follow the crowd, noncritical thinker, boastful bragguart, who ususlly feeds off others accomplishments, lacking in character...and add another, lazy ....cause you don't feel like typing out the word "chamber"...really?
Of course...The dog ate your homework!
As I mentioned, if you toss in "accuracy & precision" into the main goals of the build, then you aint using a sloppy fitment and 620.
If we are trying to gain 0.1moa on a decent dry fitment from low-cost low-effort procedure, then so be it. I think the goop does help stabilize the fitment during heating cycles, so you get whatever gains there are to be had, but there's little diff in gains between any of the bedding goops mentioned thus far. And then we factor in other things that can basically shadow out the small gain from goop, ammo/barrel/shooter.
I sure hope readers know all the work to bed is not something you see from 1-shot per target trying to match poi of sights. Any gains made can only be measured in groups of shots on same target. Almost all of the movement of barrel happens after the bullet has left the muzzle.
And then we have Camp No Bed. Makes it hard to sleep at night. Happy bedding.
If we are trying to gain 0.1moa on a decent dry fitment from low-cost low-effort procedure, then so be it. I think the goop does help stabilize the fitment during heating cycles, so you get whatever gains there are to be had, but there's little diff in gains between any of the bedding goops mentioned thus far. And then we factor in other things that can basically shadow out the small gain from goop, ammo/barrel/shooter.
I sure hope readers know all the work to bed is not something you see from 1-shot per target trying to match poi of sights. Any gains made can only be measured in groups of shots on same target. Almost all of the movement of barrel happens after the bullet has left the muzzle.
And then we have Camp No Bed. Makes it hard to sleep at night. Happy bedding.
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As I mentioned, if you toss in "accuracy & precision" into the main goals of the build, then you aint using a sloppy fitment and 620.
If we are trying to gain 0.1moa on a decent dry fitment from low-cost low-effort procedure, then so be it. I think the goop does help stabilize the fitment during heating cycles, so you get whatever gains there are to be had, but there's little diff in gains between any of the bedding goops mentioned thus far. And then we factor in other things that can basically shadow out the small gain from goop, ammo/barrel/shooter.
I sure hope readers know all the work to bed is not something you see from 1-shot per target trying to match poi of sights. Any gains made can only be measured in groups of shots on same target. Almost all of the movement of barrel happens after the bullet has left the muzzle.
And then we have Camp No Bed. Makes it hard to sleep at night. Happy bedding.
So it sounds like your opinion is that removing slop in the receiver (via thermofit/shim) has a bigger impact on accuracy/precision than bedding?
My order of operations is pretty similar. At first I will shoot an upper with no shims or bedding etc. (if it’s egregiously sloppy I will shim it right away though). If it shoots, great no more tweaks, if not I will lap & add a shim if possible then test again. If it still doesn’t shoot I will bed then as last resort try different torque settings on the barrel nut +/- 10 ft-lbs to “tune” the barrel harmonics.
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How many different "goops" have you personally used on how many different rifles?
And yes, I do agree with the fact that the shooter & the ammo can, & usually does, over ride most gains from bedding.....................very few shooters are 1/2" capable, much less 1/4"..................ditto for ammo, including Black Hills.
MM
Yeah i know you are right. But i had to troll a little and say i expected a little more specificity than “pretty hard”.
I expected you to say something like RH 15N-85.5
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Joe Carlos goes into some testing. I forget which of these videos discussed the findings, but essentially:
Thermal fit barrel extension OR shim & bedding are the options with the biggest improvements. Though still small improvements. Just bedding by itself also shows improvements, just not quite as much.
This link is supposed to be a playlist, but it is going directly to one of the videos. Look through the channel’s playlists for more.
Personally, I only ever thermal fit or do just 620. Every time I’ve tried to do shims, they get jammed up and bent as I try to insert the barrel extension. They’re a pain in the ass. Straight 620 is perfectly fine for the level of precision needed with a gas gun. There are too many other factors related to receiver flex when force is applied to the handguard. The shims are usually in the noise and provide like a 10% benefit at most.
Well, many people on the lines at Camp Perry would disagree with you about 620 not being good for precision goals. Thermal fit is ideal, but if you have a barrel extension that isn’t thermal fit, shims&620 or 620 standalone are the go-to.
Also, I’m still not sure what you refer to every time you use the word “goop”.
Edit: word
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As I mentioned, if you toss in "accuracy & precision" into the main goals of the build, then you aint using a sloppy fitment and 620.
If we are trying to gain 0.1moa on a decent dry fitment from low-cost low-effort procedure, then so be it. I think the goop does help stabilize the fitment during heating cycles, so you get whatever gains there are to be had, but there's little diff in gains between any of the bedding goops mentioned thus far. And then we factor in other things that can basically shadow out the small gain from goop, ammo/barrel/shooter.
I sure hope readers know all the work to bed is not something you see from 1-shot per target trying to match poi of sights. Any gains made can only be measured in groups of shots on same target. Almost all of the movement of barrel happens after the bullet has left the muzzle.
And then we have Camp No Bed. Makes it hard to sleep at night. Happy bedding.
Brownell's Smith busters....
All because people don't use the correct terminology certainly doesn't mean they don't how to do something. Kinda ignorant to get so offended by someone saying "spin up a barrel" pretty sure that term has been used alot by some of the best in the business... Don't think I've ever heard a gangbanger use the term either. Kinda just makes you sound like a stuck up machinist, alot like all the "engineers" I've delt with over the years. You know how to tell if someone's an engineer, just wait they'll tell you.
When I read that, I thought “well that escalated quickly”
As I mentioned, if you toss in "accuracy & precision" into the main goals of the build, then you aint using a sloppy fitment and 620.
If we are trying to gain 0.1moa on a decent dry fitment from low-cost low-effort procedure, then so be it. I think the goop does help stabilize the fitment during heating cycles, so you get whatever gains there are to be had, but there's little diff in gains between any of the bedding goops mentioned thus far. And then we factor in other things that can basically shadow out the small gain from goop, ammo/barrel/shooter.
I sure hope readers know all the work to bed is not something you see from 1-shot per target trying to match poi of sights. Any gains made can only be measured in groups of shots on same target. Almost all of the movement of barrel happens after the bullet has left the muzzle.
And then we have Camp No Bed. Makes it hard to sleep at night. Happy bedding.
I can tell you from personal experience that bedding a barrel extension on a loose fitting upper does make a difference.
I took a Criterion hybrid with a BCM blemished upper that was kind of loose and shooting around 1.5 MOA with 77 FGM-SMKs and turned it into a 0.8MOA with the use of shims and 620 goop.
I learned the process in a gun smithing class and not on the interwebz.
Certainly wasn't trying to be too hash but damn the terminology can vary alot...Getting hung up on that is just silly.
If you are manufacturing barrel extensions for this company or a government contract you must follow the print exactly in every detail, heat treatment, finish requirements, tolerances, etc...if not done to print, it's scrap and can not be sold.
But if you buy it, it's yours, and you can do anything ya want with it.
Turn it, file it, weld it, grind it, use it as a hammer...or even put some 620 on it, cause you like the aroma, but don't wish to glue anything together.
It's yours to do as you wish.
That was the funniest part about all long winded replies. It works quiet well, especially when you have a loose fitting extention. Use Silicone, because they use it in head gaskets. Like how in the shit is that even remotely related.
Then we get into the rant about spinning up barrels. What the fuck was this thread about again.
I'll machine circles around all of you, and use whatever language I want.
Anyone need something, "spun up"?
Anyone need something, "spun up"?
Brownells is a little off base, IMO...except for the interference fit is a good start.
You must shoot and test to see if what you do has any improvement and how much...and that varies from gun to gun and even to calibers to some extent.
But these accuracy enhancements make a difference...example: same day, same match ammo, factory upper vs the accuracy enhanced upper both 6mm ARC.
Brownells says, ya don't need to true the reciever face...ya actually should check it, cause as you can see, this one did not clean up with a light cut.
Check out the internal burrs on this gas port, here's a bad one. But ya dont know if ya don't check.
Truing and centering things up helps in accuracy.
The "old guy in the yellow shirt" video, actually has more valid points to add to the conversation than Brownells.
An actual test of different barrels and extensions, 10 - 3 shot groups before and after bedding the barrel extension with 620 over 5 rifles assembled showed an average of 18% increase in accuracy, better than metal shims alone. Then selecting an extension with slight interference fit that's hard to pull out and still adding 620 loctite gave the best result of 35% reduction in group size in this small study.
A total of two guys state that if you use BAT barrel extensions and torque on another BAT barrel extension that they are do precisely made that the gas port will index up close enough to use...I have not verified that, and do not plan to do so.
Whether or not you subscribe to any of these practices is up to you, and what your accuracy needs are.
For me, they work, so I'll continue to use them, until better accuracy proceedures emerge.
You must shoot and test to see if what you do has any improvement and how much...and that varies from gun to gun and even to calibers to some extent.
But these accuracy enhancements make a difference...example: same day, same match ammo, factory upper vs the accuracy enhanced upper both 6mm ARC.
Brownells says, ya don't need to true the reciever face...ya actually should check it, cause as you can see, this one did not clean up with a light cut.
Check out the internal burrs on this gas port, here's a bad one. But ya dont know if ya don't check.
Truing and centering things up helps in accuracy.
The "old guy in the yellow shirt" video, actually has more valid points to add to the conversation than Brownells.
An actual test of different barrels and extensions, 10 - 3 shot groups before and after bedding the barrel extension with 620 over 5 rifles assembled showed an average of 18% increase in accuracy, better than metal shims alone. Then selecting an extension with slight interference fit that's hard to pull out and still adding 620 loctite gave the best result of 35% reduction in group size in this small study.
A total of two guys state that if you use BAT barrel extensions and torque on another BAT barrel extension that they are do precisely made that the gas port will index up close enough to use...I have not verified that, and do not plan to do so.
Whether or not you subscribe to any of these practices is up to you, and what your accuracy needs are.
For me, they work, so I'll continue to use them, until better accuracy proceedures emerge.
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There is also a Joe Carlos video on that channel I linked, where he discusses bolt carrier tilt. I’m guessing that’s what you were trying to mitigate with the screws in the bolt carrier in your post?
