Accuracy and Upper Receivers.

bigjake83

Golden Shellback
May 19, 2013
2,464
108
63
Southern Idaho
#51
I wonder how much effect our use of glue, and/or oversized extensions/tighter receivers has on the whole thing?

Jake?

Some are nearly an interference fit, and the ones that are not almost universally get glued.
Yes it is critical to have proper fitment with the barrel Extension and Receiver. If you don't want to spend the extra $60 for a oversized barrel extension, then use High Temp Red Loctite. If we are talking about a Precision Rig then don't Half Ass it! Polishe the Barrel extension to a mirror finish, true your Receiver Face (by a Professional) and Bed or Thermal Fit the Barrel, make sure to season the receiver theads and apply some Anti Seize, and lastly don't over torque the barrel nut, 50-65 FTLBs is ideal.
 
Jun 13, 2008
630
248
43
#52
...and lastly don't over torque the barrel nut, 50-65 FTLBs is ideal.
My opinion has always been that..for the price of a lot of barrel nuts, when you reach proper torque, just cut out anything that's in the way of the gas tube. I know that isn't always an option, but if it is, it makes sense.

They are a HUGE increase in cost over a mil-spec M4, but the "comp" extensions aren't $60.

The proprietary 20TPI from Holliger is $42: https://www.whiteoakarmament.com/competition-barrel-extension-m4.html I used one on my 1,000 yard upper. Works fine. Probably entirely unnecessary, but man it checks a box for the ticky, and I do think the finer threads are a good idea.

BAT Machine's is only $31, and is standard dimensions, albeit a little larger shank, depending on which you roder, 1.000" or 0.999". I cannot for the life of me figure out why a guy spec'ing out an accuracy AR would NOT call BAT and get one of these. Given the rest of BAT's work, the extensions are probably dimensionally perfect.

https://www.batmachine.com/batactions/ar-15/

I DON"T have a BAT extension to prove that to myself, but if you've never seen a lathe-built Remington 700 action screw, man their's are truly a work of art.

Pair a 0.999" BAT with a BCM tight receiver, and there wouldn't BE any bedding. I don't think you'd get a 1.000" in without turning some material off the shank, or nitrogen fitting.

-Nate
 

whatsupdoc

Duck season
Dec 12, 2017
246
103
43
Long Island NY
#53
Unfortunately the Seekins test isn't going to happen because I'm now 0-2 in getting them to deliver me a usable receiver. My Valkyrie barrel has been bedded back into the VLTOR receiver and will be staying in it and the Seekins going back for a refund.

I've got several bolt guns and have had a ton more, almost all free floated in chassis or bedded stocks and I've never experienced any shift. The only time you're going to have any change on a bolt gun is if there's something wonky with the action to stock fitment. They're steel receivers with a lot of meat on them, they aren't going to flex enough under any normal or extreme use to see any change.


What is the issue with the Seekins upper?
 

padom

SuperMod
Staff member
Mar 13, 2013
6,261
360
83
Southeastern, Pennsylvania
#55
My opinion has always been that..for the price of a lot of barrel nuts, when you reach proper torque, just cut out anything that's in the way of the gas tube. I know that isn't always an option, but if it is, it makes sense.

They are a HUGE increase in cost over a mil-spec M4, but the "comp" extensions aren't $60.

The proprietary 20TPI from Holliger is $42: https://www.whiteoakarmament.com/competition-barrel-extension-m4.html I used one on my 1,000 yard upper. Works fine. Probably entirely unnecessary, but man it checks a box for the ticky, and I do think the finer threads are a good idea.

BAT Machine's is only $31, and is standard dimensions, albeit a little larger shank, depending on which you roder, 1.000" or 0.999". I cannot for the life of me figure out why a guy spec'ing out an accuracy AR would NOT call BAT and get one of these. Given the rest of BAT's work, the extensions are probably dimensionally perfect.

https://www.batmachine.com/batactions/ar-15/

I DON"T have a BAT extension to prove that to myself, but if you've never seen a lathe-built Remington 700 action screw, man their's are truly a work of art.

Pair a 0.999" BAT with a BCM tight receiver, and there wouldn't BE any bedding. I don't think you'd get a 1.000" in without turning some material off the shank, or nitrogen fitting.

-Nate

I dont use BAT extensions anymore because of how sharp the back side of the lugs are. Just takes nasty chunks of brass out of the cases on extraction. Now you can take a Dremel 520-02 Impregnated wheel and polish the back sides (as suggested by JP) to smooth them out which I have done and works. Pain in the ass when the extension is already on the barrel and make sure you flush everything thoroughly.

I now use JP extensions only. They are already polished and coated and are smooth as butter. Yes, they are more expensive but the best extensions I have handled.
 

padom

SuperMod
Staff member
Mar 13, 2013
6,261
360
83
Southeastern, Pennsylvania
#56
I just put my 20" Keystone Kreiger 1:7 .223 Wylde in a MEGA SBU Billet upper and lower with a YHM 15" TJ Competition handguard. Talk about a tight fitting upper/lower and a beefy upper. Thats an understatement. I honestly though the upper/lower didnt fit together till I got it perfectly straight up and down and pressed it into the lower. Ive built a lot of AR's from all kinds of forged and billet receivers but this is by far the tightest set EVER.

On sale at JSE Surplus right now. Hard to beat this price for one beefy, tight fitting setup.


Regular MEGA SBU Upper

http://www.jsesurplus.com/AR-15SBUBilletUpperwithoutSideChargingHandleSlotJSEEXCLUSIVE.aspx

Side Charging MEGA SBU Upper

http://www.jsesurplus.com/AR-15SBUBilletUpperwithSideChargingHandleSlotM0300JSEEXCLUSIVE.aspx

MEGA Billet Lower

http://www.jsesurplus.com/megaarms-4-1-1.aspx
 
Jun 13, 2008
630
248
43
#57
I dont use BAT extensions anymore because of how sharp the back side of the lugs are. Just takes nasty chunks of brass out of the cases on extraction. Now you can take a Dremel 520-02 Impregnated wheel and polish the back sides (as suggested by JP) to smooth them out which I have done and works. Pain in the ass when the extension is already on the barrel and make sure you flush everything thoroughly.

I now use JP extensions only. They are already polished and coated and are smooth as butter. Yes, they are more expensive but the best extensions I have handled.
I do exactly what you quote.

Ordering John Holliger's 20TPI extension a few weeks before the barrel blank arrives, I, uh "work on it" to deburr and polish everything I see that needs it, with the obvious exception of load bearing surfaces, threads, etc.

It also gives me a chance to test fit in the upper, and to hand-fit the M4 extensions to the receiver to create one 'seamless' polished ramp.

Works.

My most recent one is on my 1,000 yard upper, and that brass needs all the integrity-help it can get!

-Nate
 
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