Complete 7.62x39 Upper on my Bushmaster Ar-15 lower
I have been looking at getting a complete upper in 7.62x39 to drop onto my Bushmaster 223 lower. Looking at Bear Creek uppers and looks like they will just drop onto my lower but will a 7.62x39 magazine fit and function in my 223/5.56 lower and what magazines are recommended for this? Do I need to replace any other parts or is the mag all I need to fire 7.62x39 ammo? The Bear Creek uppers have upgraded firing pins and extractors to handle the surplus steel case ammo. Thanks for any suggestions or advice!
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c products mags with the proper curve drop it on and good luck
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I've not been very pleased with BCA barrels/uppers. Three or four years back, I bought a complete 6.5Grendel upper. Got it zeroed and went hunting. Bad idea- I discovered that the barrel nut(free float handguard) had loosened during zeroing and the rifle no longer functioned. I sent it back for repair and before I got it zeroed again, the gas block came loose and sort of rocketed out of the handguard. Back to BCA again and didn't return in time to hunt with it as I'd hoped. When it did come back, the gas block came loose within 5-8 shots.
I put it on a shelf and during this past winter, I stripped everything down, cleaned all the parts, and re-assembled using a new upper, barrel nut, and handguard. So far, I've put maybe 25 rounds through the rebuilt parts and all is intact and accuracy is sort of OK in a good enough for deer @ 200 yards sort of way. This is a HBar profile fluted barrel so should be better than 1.5 MOA with domestic commercial ammo. Don't even think about WOLF, that 4-5 MOA on a good day.
No more BCA barrels of completed uppers for me.
As far as swapping uppers, usually there' s no problem. Some users find that a heavier hammer spring is required but I haven't had this issue. I use ASC 10 round mags for hunting and have ASC and Stoner 30's(nominally 27-28 rather than 30) in case I need to repel boarders. No longer available but very functional are the TherMold plastic mags-haven't seen them for sale lately. I have three 7.62x39 uppers (2x 16" and a 10.5") and no real issues with any of them. The 10.5" pistol upper is a real "HOLY COW" piece complete with fireball and concussion BUT it's every bit as accurate as I can hold it.
BELOM brass case, boxer primed ammo available now is pretty darned good for blasting. Hornady steel case hunting ammo loaded with SST bullets is great. PPU 123 grain RNSP is good but won't feed in my guns.
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I have 4 BC uppers, including X39 and no issues. But there are plenty of other makers out there too. For X39 I add a stronger FP spring and that's about it.
I think ASC is the latest version of CProducts and they work fine. I keep the 30 rounders at 28 IIRC.
There's another mag brand out there, has "V" stamped ribs on the sides and they work best for me - D&H Industries.
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"For X39 I add a stronger FP spring and that's about it."
Are you sure you didn't mean 'a stronger hammer spring'? AR's don't have FP springs.
I did use a slightly longer firing pin on one upper that's designated for use with European made ammo but found it wasn't needed on the Hornady steel case hunting ammo, BELOM factory, or my handloads.
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What about a stronger recoil spring or heavier buffer weight?
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"What about a stronger recoil spring or heavier buffer weight?"
I have not found it necessary to change either from the normal 5.56/.223. Since the 7.62x39 is using approx 10% more powder burned in bore of 90% larger cross section, the gas available at the port is significantly less in the 7.62 than a normal .223. This is offset by using a larger port which is adjusted to meet the functional requirements of the system with standard buffer and spring.
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