Gunsmithing Ar10 barrel fittment in upper receiver

[Jakediesel06]

I’m in the process of building a 6.5 creedmoor. And Trying to make it as much of a precision rifle that I can. I am by no means a gun smith and this is just a hobby I’m trying to learn the right way to do things. That being say the barrel fits in my upper receiver a little looser than I would like it too. When I tight down the barrel nut it’s solid. But I think that with out the barrel nut on the barrel should be tighter inside the upper. Is there a way to tighten this fit up. By maybe knurling the barrel extension to gains a few thousands.
Barrel measures 1.187
Upper measures 1.192
Thankyou for your time.

 

[padom]

Its not going to make a difference. Ive done testing on a custom Bartlein 22" 6.5cm barrel on an Aero Precision M5 upper receiver vs a MEGA upper receiver. With the Aero M5 upper, the barrel slipped right in and had some play but the barrel nut tightens that right up. With the MEGA upper you have to thermofit the barrel by heating up the front of the upper with a heat gun so it expands, then you insert the barrel, torque your barrel nut and let cool making for a super tight barrel to upper fit.

The bottom line, accuracy was the same with this barrel on both uppers.

Remove the barrel, apply 609 or Rockset liberally to the barrel extension then slip it into your upper and torque the nut. Let dry overnight and go shoot the damn thing.


Here's how the Bartlein shot in the Aero upper with the sloppy fit.

 

[Jakediesel06]

Thankyou. I’m trying to up load a video. Haven’t figured out how yet. It is an aero upper seems like it has more play than it should.

 

[Jakediesel06]

Would you recommend one over the other between the rock set and loctite

 

[padom]

Ive used both, both are good to go. Just order some Rocksett

 

[Jakediesel06]

Any reason you are opposed to knurling or just because loctite is easier and cheaper?

 

[knuckleballz]

Brownells has a shim kit for 20$ if you want to thermofit

 

[Jakediesel06]

Do you have a link to this kit?

 

[colchester]

I dont think you will be able to knurl the barrel ext. They are pretty hard

 

[knuckleballz]

It is listed as AC-24 shim stock kit on Brownells

 

[Jakediesel06]

Thankyou

 

[Velocity Chad]

I've always used loctite 620. Any of the sleeve retsiner compounds, or eaven regular loctite is likley fine. I can't say it makes a big difference, but I've assembled quite a few shooters.

 

[Jakediesel06]

Just for a littl quick info for me in the future. It sounds like mega, jp are “press fit” barrel to upper receiver mating? Are there any others that you anyone would consider a press fit.

 

[padom]

I believe 2A Armament but dont quote me on that. I use MEGA sets for all my large frame AR's. BCM for AR15's is a thermofit.

 

[Billiam1211]

Question regarding headspace on a AeroPrecision M5 Build:

Yesterday I swapped out barrels on my M5E1 and put on a BA 20" 308 Bull Barrel. I checked headspace with Forester Go & NoGo Gauges. The interesting part is when I checked the headspace with the barrel out of the upper, both gauges worked as expected indicating headspace is safe. However when I assembled the upper, I put the NoGo gauge in and the bolt closed completely on the NoGo gauge. Wondering if anyone has experienced this before. The assembled upper method with the NoGo gauge forcing the bolt to stay out of battery is what I saw on Brownell's tutorial section.

Would you guys say the rifle is safe to shoot considering headspace gauges passed the test with the barrel removed?

Thanks,
B

 

[B y r o n]

The only thing I can think of is this: When you tested things when the barrel was out you couldn't get the bolt head in the barrel extension with just your fingers. But, once the barrel was in the action you could get the bolt to close on the no-go gauge. Was this just using hand pressure or was the buffer spring driving it?

 

[padom]

if it closes on a no go then I would not shoot it.

 

[Jakediesel06]

Guessing the bolt fully engaged and is not partically engaged. Did you use the buffer spring to help you engage or use your fingers. More force can be created that way than using your fingers. My .02 is they call it a no go gauge for a reason thou.

 

[Billiam1211]

With the barrel out I simply inserted the NoGo into the bolt head without the ejector, then placed into the chamber and attempted to turn and it would not turn. I then assembled the upper receiver with the barrel torqued to about 50 ft lbs. With the NoGo gauge still in the bolt without extractor, I inserted the assembled BCG into the upper with hand pressure and the entire BCG closes flush with the upper. I'm kind of thrown off by the results.

 

[padom]

my no go will not let the bolt go fully into battery on any of mine

 

[Billiam1211]

Thank you for the feedback gentlemen. I'm going to go visit the local gunsmith and chat or call ballistic advantage for a barrel exchange.

 

[Jakediesel06]

I believe 2A Armament but dont quote me on that. I use MEGA sets for all my large frame AR's. BCM for AR15's is a thermofit.

BCM stands for bravo company right?

 

[eklarsen]

yes

 

[Jakediesel06]

Anyone fimilar with Wilson combat and how there upper receiver fits the barrel?

 

[Jakediesel06]

Used .0025 shim wrapped around barrel extension pressed in nice and smooth took all the wobble out.