Flattop AR15 uppers in 7.62x39 Who makes a good one?


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R.W.Dale
December 3, 2006, 07:17 PM
I'm starting to kick around the notion of building me an AR15 in x39 using one of these lowers http://ar47.com/pics.html I'm looking for a 20 barreled flattop. Do any of you guys have any suggestions?

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rbernie
December 3, 2006, 09:37 PM
Hving tried twice to make 'em go, I've decided that 7.62x39 and 20" barrels in an AR platform don't mix for general purpose use. The issue you'll run into is short-stroking; lots and lots of it.

My personal opinion is that the bore is too large (expansion ratio) for the round to provide sufficient gas to cycle the action EVERY SINGLE TIME, even with the gas port drilled wide open (.125"). You can try to compensate for the lack of gas pressure by running lightweight bolt carrier bits and low rate action springs, but then stripping rounds from the magazine and chambering them in the field becomes less reliable (and chances are the rifle *still* isn't going to be 100%).

I can get 16" 7.62x39 ARs to run all day long, and one is my primary hunting arm. But I've given up trying to get a rifle length barrel to run.

Last I checked, DPMS made 16" 7.62x39 uppers but only in A2 form. I build my own using flattop uppers and Shaw barrels.

R.W.Dale
December 3, 2006, 09:41 PM
OK that makes good sense, even handloading you won't be able to use a slow enough powder in the x39 to keep the port pressure up on a 20" tube. So 16" it is:) what uppers are you using?

rbernie
December 3, 2006, 11:54 PM
I use DPMS HiRise (http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=695366) uppers for the target-oriented uppers (mounting a scope with Leupold Rifleman low matte rings) and CMMG (http://cmmginc.secure-mall.com/shop/?shop=1&cart=499714&cat=30&) uppers for the fightin' carbines (mounting optics with ARMS mounts, mostly).

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