Question regarding barrel fitting

[constructor]

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.

[ST911]

Initial fitment, bedding or sealant, torque value, shims, lapping, etc can all matter. To who, when, and how will vary.

[DwayneZ]

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]

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]

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]

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

[georgeib]

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]

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

[3 AE]

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".

[AndyLate]

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