View Full Version : Question regarding barrel fitting
WornOutGrunt
10-12-22, 06:55
Hi,
I'm putting together a new build, and I test fitted the Centurion barrel to the receiver ( Square forge) and there was a little play in it ( I did not need to Thermofit)
So my question is should I use Loctite 620 to tighten up /lock it to receiver or do you think just barrel nut torque will be enough. I don't have any shims to go over barrel extension which is why I'm asking about the Loctite 620.
Any replies would be appreciated.... I'm hoping the Centurion Arms barrel shoots well ( as it was purchased used..)
I don’t use that stuff on barrels. Gas keys yes, barrels no.
I’d be curious what SOTAR would say about this one, if he is browsing and sees this question.
I’ve had exactly one where I used a single layer of annealed stainless shim stock of .001 thickness and it appeared to work well.
It was a fairly extreme case and while it worked, it probably would have been better to try another upper as Mark suggests below or buy a better barrel.
If the rifle is not being built for precision rifle matches, I would not use Loctite or do anything special when installing the barrel.
Definitely NO on the loctite. Barrel nut only or try a new upper. The forge mark only tell you who made the platter. Any machining after that has nothing to do with the forging.
WornOutGrunt
10-12-22, 11:50
It is not a 'precision' build but I want to squeeze the best accuracy I can out of it. The upper was unfired, but it did have a barrel in it.. which I foolishly did not test for accuracy but.. I'm hoping that the hype over Centurion barrel accuracy lives up to it's preceded reputation.
I wanted to call Centurion but there is no listed number so.. I figured I would post here as many people have run their barrels to ask this question. I know Criterion had a video where they used the Loctite but I think this site is a little bit better with real world information.
I don’t use that stuff on barrels. Gas keys yes, barrels no.
I’d be curious what SOTAR would say about this one, if he is browsing and sees this question.
I’ve had exactly one where I used a single layer of annealed stainless shim stock of .001 thickness and it appeared to work well.
It was a fairly extreme case and while it worked, it probably would have been better to try another upper as Mark suggests below or buy a better barrel.
Per my notes from SOTAR class:
The AMU reported a 7% consistency improvement when lapping the upper and bedding barrels with Loctite 620.
Per my notes from SOTAR class:
The AMU reported a 7% consistency improvement when lapping the upper and bedding barrels with Loctite 620.
I would perform this procedure when building a rifle used for High Power Rifle competition. For a general use carbine or rifle, I wouldn't go to the trouble.
I've assembled uppers that had a slight amount of play between the barrel and receiver, without lapping and bedding, that shot sub-MOA at 300 yards.
It is not a 'precision' build but I want to squeeze the best accuracy I can out of it. .
Then there's no reason not to bed the barrel with Loctite. It's a simple 10 minute procedure (plus curing time).
I'm hoping that the hype over Centurion barrel accuracy lives up to it's preceded reputation.
If you're referring to Cenutrion's CHF barrels, they're chrome-lined NATO chambered barrels manufactured by FN and accuracy/precision will be commensurate with the particular profile of the barrel and the ammunition that you're using. The Centurion CHF 16" mid-length barrel (1 pound, 10 ounces) that I tested was good for approximately 1.4 MOA using match-grade hand-loads.
..
ClearedHot
10-12-22, 17:37
Then there's no reason not to bed the barrel with Loctite. It's a simple 10 minute procedure (plus curing time).
If you're referring to Cenutrion's CHF barrels, they're chrome-lined NATO chambered barrels manufactured by FN and accuracy/precision will be commensurate with the particular profile of the barrel and the ammunition that you're using. The Centurion CHF 16" mid-length barrel (1 pound, 10 ounces) that I tested was good for approximately 1.4 MOA using match-grade hand-loads.
..
Molon,
Slightly off topic but have you done any testing of DD's S2W 18" barrels? They're a chrome lined CHF barrel with HBAR profile. Was considering one for a SPR'ish build.
gunnerblue
10-12-22, 17:45
Hi,
I'm putting together a new build, and I test fitted the Centurion barrel to the receiver ( Square forge) and there was a little play in it ( I did not need to Thermofit)
So my question is should I use Loctite 620 to tighten up /lock it to receiver or do you think just barrel nut torque will be enough. I don't have any shims to go over barrel extension which is why I'm asking about the Loctite 620.
Any replies would be appreciated.... I'm hoping the Centurion Arms barrel shoots well ( as it was purchased used..)
Which Centurion barrel and what kind of ammo? If it's one of the CHF barrels and you're not shooting precision ammo I doubt you'll see a significant improvement. Mine are all about 1.5 MOA shooters with 62 grain Hornady handloads and factory Gold Dot. All are mounted in either Vltor or BCM uppers, the BCM of course being a very tight fit.
IMO.. Bedding, shimming and truing have NO value other than to the plumbers charging you to do it!!!
All of my builds, precision or not, deliver MOA or better. None of them required heat to assemble. The less than .1" theoretical improvement is in no way worth it to me unless competing at a fairly high level.
the AR-15 Junkie
10-12-22, 20:42
IMO.. Bedding, shimming and truing have NO value other than to the plumbers charging you to do it!!!
100% Agree!
Any replies would be appreciated.... I'm hoping the Centurion Arms barrel shoots well ( as it was purchased used..)
With a good bore scope (good enough for task but not be prohibitively expensive) you can look at a gas port and easily see the difference between something than has never been fired, something that has been 'test' fired and something that has been fired a few cases of ammo worth.
Cheap tool to have considering what a good barrel can cost in comparison.
Plumbers charging us? Some of us are capable of performing these procedures so no one gets charged.
WornOutGrunt
10-13-22, 06:47
Thank you to all who replied. The barrel I will be using is
https://centurionarms.com/lightweight-hammer-forged-barrel-midlength/
As stated it is a used barrel but only had a couple hundred rounds thru it ( no mag dumps) My range would not be any more than 400m maximum for this set up..
I have a 4-5 different loads, all heavy for caliber, ( all factory) to try...I will not be using any handloads.
I will report back soonest once I have completed the build. I fitted a Aero G/B on there ( as I didnt have the Centurion tabbed one) and it seemed to fit snuggly.
I thank you all again for your input... All of you have a great deal of knowledge and appreciate all of your input
IMO.. Bedding, shimming and truing have NO value other than to the plumbers charging you to do it!!!
100% Agree!
Yep, I put all that stuff in the shade tree gun plumber category... People are free to experiment with it, but I've never felt the need for it personally.
I don’t use that stuff on barrels. Gas keys yes, barrels no.
You use Green Loctite on gas keys? Not Permatex 3D?
You use Green Loctite on gas keys? Not Permatex 3D?
This is what I use as a bedding / sealant compound on gas keys.
If it’s good enough for SOTAR it is good enough for me.
I level the key surface on a stone and put the 620 on the carrier before mounting torquing and staking.
ETA: I also use OCK screws on all my keys.
https://uploads.tapatalk-cdn.com/20221013/06c91d88963783da200cd1198e97b53f.jpg
If you install the barrel without using Loctite and you don't like the way the carbine shoots, you can remove the barrel and bed it with Loctite later.
constructor
10-14-22, 08:37
Hi,
I'm putting together a new build, and I test fitted the Centurion barrel to the receiver ( Square forge) and there was a little play in it ( I did not need to Thermofit)
So my question is should I use Loctite 620 to tighten up /lock it to receiver or do you think just barrel nut torque will be enough. I don't have any shims to go over barrel extension which is why I'm asking about the Loctite 620.
Any replies would be appreciated.... I'm hoping the Centurion Arms barrel shoots well ( as it was purchased used..)
This and truing the receiver topics have been beat to death over the last 20 years. Both procedures have been used by highpower shooters since the 80s.
Many rifles are built on the kitchen table like a jigsaw puzzle and if all they do are mag dumps they will make noise and work fine sometimes.
Those that want to get the most out of accuracy will do everything they can to increase accuracy. Some understand that the receiver /barrel connection is how the scope is connected to the barrel. Think about how much trouble and expense people go through to buy or make one piece bolt gun actions like Surgeon.
If all you need is the military requirement of 3 MOA at 100 yards and use iron sights or red dots then no truing the receiver and bedding the barrel is probably a wasted effort.
Initial fitment, bedding or sealant, torque value, shims, lapping, etc can all matter. To who, when, and how will vary.
One of my fave topics.
Post #13 is not 100% accurate.
One needs to understand "fitments" to really understand the topic of this thread.
Facing the receiver, bedding compounds, shimming, yada yada yada, ALL impact how the muzzle end of the barrel will move around as the parts heat cycle. There will come a point where you achieve the "best" fitment, then barrel harmonics become dominant factor.
Keep the bambam going. Cheerio.
joedirt199
10-24-22, 06:46
I have stolen feeler gauges from my set in the past for shim material. The loctite is harder to remove if you want to move the barrel to a different receiver.
WornOutGrunt
10-24-22, 09:04
So just a quick update to this thread
I DID end up using Locktite on this build..
My results were as follows ..( I was only able to do the testing at 50Yds so I think that the results would be double at 100yds...not really sure how that works)
All shot off a bag/ bench..2-4 sec between shots 60 deg F no wind
Centurion 16" with Vortex 1x4 Glass
Sig 77g OTM- 0.4 and 0.6 ( edge to edge/ 2 groups fired)
Wolf 55g - 1.4" and 1.6"
Armscore 55g - 1.8 and 2.1"
SOLGW 13.7 with PA Red Dot and Vortex Magnifier
Sig 77g OTM - 0.5
Wolf - 1.3
Armscore- 1.6"
The Centurion didn't seem to like the 55g stuff as much.. but I wasn't using any LC M193 or any 62g stuff ( cause I'm a dumb ass and forgot to bring it)
I guess I was expecting more out of the Centurion than I got. It seems on par with a BA Modern Series bbl which is 1/2 the price..
I may try to get some M193 thru it or some Hornady 62g... I can post that when it happens
Hammer_Man
10-24-22, 10:43
So just a quick update to this thread
I DID end up using Locktite on this build..
My results were as follows ..( I was only able to do the testing at 50Yds so I think that the results would be double at 100yds...not really sure how that works)
All shot off a bag/ bench..2-4 sec between shots 60 deg F no wind
Centurion 16" with Vortex 1x4 Glass
Sig 77g OTM- 0.4 and 0.6 ( edge to edge/ 2 groups fired)
Wolf 55g - 1.4" and 1.6"
Armscore 55g - 1.8 and 2.1"
SOLGW 13.7 with PA Red Dot and Vortex Magnifier
Sig 77g OTM - 0.5
Wolf - 1.3
Armscore- 1.6"
The Centurion didn't seem to like the 55g stuff as much.. but I wasn't using any LC M193 or any 62g stuff ( cause I'm a dumb ass and forgot to bring it)
I guess I was expecting more out of the Centurion than I got. It seems on par with a BA Modern Series bbl which is 1/2 the price..
I may try to get some M193 thru it or some Hornady 62g... I can post that when it happens
The Centurion will probably outlast any BA barrel. Just my .02
So just a quick update to this thread
I DID end up using Locktite on this build..
My results were as follows ..( I was only able to do the testing at 50Yds so I think that the results would be double at 100yds...not really sure how that works)
All shot off a bag/ bench..2-4 sec between shots 60 deg F no wind
Centurion 16" with Vortex 1x4 Glass
Sig 77g OTM- 0.4 and 0.6 ( edge to edge/ 2 groups fired)
Wolf 55g - 1.4" and 1.6"
Armscore 55g - 1.8 and 2.1"
SOLGW 13.7 with PA Red Dot and Vortex Magnifier
Sig 77g OTM - 0.5
Wolf - 1.3
Armscore- 1.6"
The Centurion didn't seem to like the 55g stuff as much.. but I wasn't using any LC M193 or any 62g stuff ( cause I'm a dumb ass and forgot to bring it)
I guess I was expecting more out of the Centurion than I got. It seems on par with a BA Modern Series bbl which is 1/2 the price..
I may try to get some M193 thru it or some Hornady 62g... I can post that when it happens
FWIW, I did not see any reduction in group size when slow firing. I did see a marked reduction in stringing and group shift when hot though.
I used hardened stainless shim stock purchased via Amazon, which is available in a variety of thicknesses. I had one upper which had a 0.002" variation between the inner bore of the receiver and the outer diameter of the barrel extension. I wrapped a 0.001" piece of shim stock around the extension and using heat on the upper and freezing of the barrel was able to get them fitted. Had another that had a 0.003 variance, and instead of buying 0.0015" shim stock, I opted to just wrap the 0.001 stuff one and half times around. With the extra half turn around the bottom of the extension.
Both times gave me the same results. Absolutely plan on doing so with future builds.
WornOutGrunt
10-24-22, 15:08
As I mentioned this testing was done at 50yds... How much should I expect the groups to open at 100 yds ? ?
I can factor in elevation holds/ trajectory, but just wondering if it is accurate to assume the group size would double at 100 yds
I would rather shoot three ten round groups with the ammo that performed the best with each barrel at 100 yards and have a better idea of what me and my rifle can do with those combinations. Extrapolating from 50 to 100 yards is guess work.
So many times I've heard, "That so and so rifle/carbine shoots better than I can shoot". My take on that "Is that the rifle only shoots as good as the shooter behind it".
Typically groups are measured center to center, not edge to edge. You can measure outer edge to outer edge and subtract one bullet diameter or measure outer edge to inner edge. As 3AE pointed out, its hard to predict 100 yard groups by looking at 50 yard groups.
The 55gr FMJ ammo does not shoot well enough to determine accuracy potential of the barrel.
In my opinion, based on shooting a pretty fair number of groups, you would need a more powerful optic and shoot only the Sig ammo (out of the three types you mentioned) at 100 yards/meters for a realistic comparison.
I may be quite a bit older (or blinder) than you are, but I struggle with less than 6 or 7X at 100 yards and more magnification is better
Andy
My preference when testing for mechanical accuracy with firearm (long gun)/ammo is “plenty of glass”; 2-10X minimum at 100 yds. A 1-4X at 100 yds, even 50 yds, isn’t enough magnification for me to begin to evaluate true potential of a gun/ammo combination.
I used hardened stainless shim stock purchased via Amazon, which is available in a variety of thicknesses. I had one upper which had a 0.002" variation between the inner bore of the receiver and the outer diameter of the barrel extension. I wrapped a 0.001" piece of shim stock around the extension and using heat on the upper and freezing of the barrel was able to get them fitted. Had another that had a 0.003 variance, and instead of buying 0.0015" shim stock, I opted to just wrap the 0.001 stuff one and half times around. With the extra half turn around the bottom of the extension.
Another reason every guy that does his pee while standing should have some Nitrous Oxide around somewhere.
A few seconds in front of that spray and that barrels extension (or whatever item you are trying to rapidly freeze) is frozen.
WornOutGrunt
10-26-22, 05:17
I would concur with gaijin and the other poster that suggested better glass... I would have used that to T&E the barrel and the loads I just don't/ didn't have anything better..
(actually I do have a 1x6 but the center dot is 2moa and seems to cover the target more) the Vortex is 1moa dot.
I will continue on this quest and try some other loads.... Ballin on a Budget is tough...
I would certainly always welcome any advice and constructive criticism
I will post some additional test loads as soon as available
Another reason every guy that does his pee while standing should have some Nitrous Oxide around somewhere.
A few seconds in front of that spray and that barrels extension (or whatever item you are trying to rapidly freeze) is frozen.
Wow, didn't think of that! I actually had the barrels in the freezer for a couple hours instead.
gunnerblue
10-26-22, 09:27
As I mentioned this testing was done at 50yds... How much should I expect the groups to open at 100 yds ? ?
I can factor in elevation holds/ trajectory, but just wondering if it is accurate to assume the group size would double at 100 yds
Not necessarily, the only way to know for sure would be to shoot a group at 100 yards. I use no less than 10x magnification when shooting groups at that range as I would have trouble calling my shots otherwise.
Not necessarily, the only way to know for sure would be to shoot a group at 100 yards. I use no less than 10x magnification when shooting groups at that range as I would have trouble calling my shots otherwise.
I use the rule of three. Multiple the group size by three when doubling the distance fired. That should give you an honest expectation of accuracy.
We did this experiment a few years back. Stubborn Mule upper reciver with a Larue Stealth barrel. Receiver to barrel extension was fine but not tight and didnt need thermal fitting. Rail was a Geissele MK8 tightened to their spec. Upper was broken in and shot 100 rounds for a total of 125 rounds. Upper was accuracy tested with Fed GMM and shot average 1.2 moa with 10 rounds (two 5 shot groups). Upper was disassembled, trued in a lathe, add green loctite, rail tightened to spec. Upper shot .8 with same box FGGM. Accuracy was stellar out of that upper until the barrel was swapped to a V Seven. Now its a laser.
Constructor's post is spot on.
Accuracy was stellar out of that upper until the barrel was swapped to a V Seven. Now its a laser.
Does that mean better or worse?
Better. I kind of always hated that Larue barrel. It was really finicky about it's level of cleanliness. The V seven is a much better barrel in my opinion with a lot less weight.
vicious_cb
10-29-22, 15:14
Better. I kind of always hated that Larue barrel. It was really finicky about it's level of cleanliness. The V seven is a much better barrel in my opinion with a lot less weight.
Larue barrels were much better when they were made by Lothar-Walther. Definitely eyeing V-seven barrels if I ever shoot out my Noveske since V-seven seems to be the spiritual successor to the original John Noveske barrels.
fedupflyer
05-16-24, 22:05
IMO.. Bedding, shimming and truing have NO value other than to the plumbers charging you to do it!!!
100% Agree!
I just completed a AR accurizing course and one of the (main) things that we did was truing the receiver face, shimming the barrel if needed and bedding the barrel using green loctite.
In my case the groups went from 1.3 and 1.47 MOA at 100 yds
to .53 and .88 MOA.
Roughly cut my groups in half.
Not bad for a chrome lined barrel and less than $5 in extra materiel.
That is if you are actually interested in accuracy.
Any information to share from the course?
I just completed a AR accurizing course and on on the (main) things that we did was truing the receiver face, shimming the barrel if needed and bedding the barrel using green loctite.
In my case the groups went from 1.3 and 1.47 MOA at 100 yds
to .53 and .88 MOA.
Roughly cut my groups in half.
Not bad for a chrome lined barrel and less than $5 in extra materiel.
That is if you are actually interested in accuracy.
Heh, this one got bumped. Amazing what you can learn in a relatively short period of time.
I've now using lapping compound on my receiver faces and will start using the 620 product to fill any imperfections in that dimension.
There is always something more to learn in this "hobby" for lack of a better term.
Yes, please share some tidbits.
fedupflyer
05-17-24, 11:08
Heh, this one got bumped. Amazing what you can learn in a relatively short period of time.
I've now using lapping compound on my receiver faces and will start using the 620 product to fill any imperfections in that dimension.
There is always something more to learn in this "hobby" for lack of a better term.
Yes, please share some tidbits.
Here a just a few things that pop into my brain as I am typing
Buy a/an undersized upper so you don’t have to shim
use a reaction rod for barrel installation
use a receiver facing tool
use 200 or 300 grit for lapping compound maybe a combo of the two
green loctite over red for bedding a barrel
yes you can remove a bedded barrel, just takes some heat and a little pounding
use chemical and a wire brush to remove loctite (I used a steel automotive brush and goof off)
forged over billet
check feed ramp fitment into the upper and sharpness of the feed ramps
nitride barrel over chrome for hard use barrels
chasing your threads is helpful for a new build, def want to do it for a rebuild
remove bolt from BCG to test smoothness of fitment into gas tube and push up slightly while moving the carrier back and forth
buffer tube should be smooth can hone it with a brake honing tool if needed
use shims for timing muzzle device
using a bore-scope can be scary
One of my fave topics.
Post #13 is not 100% accurate.
Post #13:
100% Agree!
Are you saying you know more about what he agrees with than he does?
:blink:
John mckimb
06-14-24, 16:56
It is not a 'precision' build but I want to squeeze the best accuracy I can out of it. The upper was unfired, but it did have a barrel in it.. which I foolishly did not test for accuracy but.. I'm hoping that the hype over Centurion barrel accuracy lives up to it's preceded reputation.
I wanted to call Centurion but there is no listed number so.. I figured I would post here as many people have run their barrels to ask this question. I know Criterion had a video where they used the Loctite but I think this site is a little bit better with real world information.
This site is definitely not "better with real world knowledge" than criterion. Criterion knows more abput barrels than anyone here (i say that with confidence). However, they are focused on supreme accuracy here. They also dont recommend pinning gas blocks, which most users recommend (me included!).
On a daily use carbine i wouldnt bother loctite the barrel extention.
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