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Ok I know that there's a bunch of stuff on the interwebs about this but anyone here have experience or thoughts on an AR in AK calibers?

Thinking about putting one together. What is the best buffer tube length? Spring and buffer? Length of barrel? BCG?

Or is it a bad idea?
 
If you're talking about 5.45, just treat it like .223, can't say anything about 7.62 but I'd assume you want a heavier buffer spring. For gas length, I'd just look at another AK and go similar. Or carbine length with adjustable gas block
 
5.45 and 7.62x39 seem to be the only somewhat affordable ammo available these days. Still researching buffer weights and gas blocks myself. Leaning more toward 7.62x39 as 5.45 parts tend to be harder to find. Some research suggests that 5.45 tends to burn through barrels quickly. Anyone with experience on 5.45 barrel life?
 
5.45 and 7.62x39 seem to be the only somewhat affordable ammo available these days. Still researching buffer weights and gas blocks myself. Leaning more toward 7.62x39 as 5.45 parts tend to be harder to find. Some research suggests that 5.45 tends to burn through barrels quickly. Anyone with experience on 5.45 barrel life?
Which is interesting because an AK74 is good for quite a few thousand rounds
 
I tinkered around with a 5.45 and a 7.62 AR builds. Got some great deals on barrels so I thought I'd give it a try.

For the 5.45, I didn't do anything special other than 5.45 barrel (16") and 5.45 BGC (and mags). I think I got a bad barrel though, first round would always fail to extract and I'd have to hammer it out from the muzzle. Eventually just threw the barrel away and called it quits. Still looking for a AK74 to spend the rest of my ammo on, haha.

For the 7.62x39, I spent some more time on. I got a good deal on a 10.5" barrel, and bought a 7.62x39 BCG. Also bought a enhanced firing pin, for harder primers, and a Wolff extra power hammer spring. Had some reliability issues with cycling, but after tinkering with it finally got it work, mostly.

All in all it was fun to tinker with, but I would never trust them personably for anything other than a toy. I've decided I still want something in 7.62 and 5.45, but I want to spend the extra on a AK platform.
 
@Kruel J @Stomper either you two know?

Seems to me 5.45 x 39 would be just fine in the platform, but running 7.62 x 39 you are going to have a hard challenge finding reliable magazines to feed it because of the straight walls in the magazine well, plus the bolt face is honed out for the larger shell casing base that makes the bolt lugs more delicate.

IMHO- I'd give the 7.62 x 39 a pass in the AR15 platform, unless you went with the "AR-47" lower that runs true AK mags.
 
I have an AR in 7.62x39mm. Two issues with it are 1) the weak-point is the thinned ring around the bolt face which is known to result in broken lugs (keep a spare bolt just in case), 2) weak primer strikes with the typical AR15 firing pin; it is just a tad too short to reliably touch off the primer in typical 7.62x39 ammo which have deeper recessed primers (I bought an extended firing pin to solve that issue, but those are hard to find). But given those, it shoots very nicely and eats cheap ammo.
 
I have an AR in 7.62x39mm. Two issues with it are 1) the weak-point is the thinned ring around the bolt face which is known to result in broken lugs (keep a spare bolt just in case), 2) weak primer strikes with the typical AR15 firing pin; it is just a tad too short to reliably touch off the primer in typical 7.62x39 ammo which have deeper recessed primers (I bought an extended firing pin to solve that issue, but those are hard to find). But given those, it shoots very nicely and eats cheap ammo.

An extended firing pin would also increase the risk of slam fires.... ;)
 
I have a 10.5" upper and it was undergassed if anything. I bought the jp extra power buffer spring, wolff extra power trigger spring, enhanced firing pin, 7.62x39 shaped extractor and with supers it ran like a top.

Problem was when the silencer went on it would only cycle brown bear subs. SB subs with a 160 something bullet wouldn't cycle the bolt.

I had the gas hole drilled to.1, had to run the Taccom ultralight delrin buffer, and added a superlative arms adjustable gas block. After all those mods, I've got a soft shooting 7.62 pistol that eats everything.

The journey was arduous but enjoyable.
 
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An extended firing pin would also increase the risk of slam fires.... ;)
True, for softer primers. But in my experience most 7.62x39 ammo have really hard primers so I'm not worried about it. I also didn't mention I had to install a high-power hammer spring to overcome those hard primers, in addition to the extended firing pin.
 
I've built several Ar uppers in 7.62x 39. The combo of the specific barrel and mags I use make them very reliable and quite accurate compared to most ak's. For a 16" build, carbine gas works great and a h2 buffer is about right with the size of the gas port in the barrels I use. I have around 5000 rds through one and 1 broken extractor is all that I have had fail. I use a kak bolt with an enhanced firing pin. The lower I use has an alg trigger with standard springs and it ignites all ammo without fail. Cleaning it every 750 rds or so keeps it humming right along and I run a lot of wolf steel through it. With wolf military classic 123 hp ammo it shoots honest 1-1/8" 5 shot groups. This Ar goes to the range with me almost every trip.
 
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I also have had good luck with a young manufacturing 7.62x39 bolt which is supposed to be more robust but I have yet to break a lug on the kak bolt. The barrels I use advertise an ak spec chamber so I think extraction is aided by the more generous tolerances, especially with steel cased ammo.
 
I bought one from AR-stoner and the upper it worked well for me. The hammer spring was a bit weak so I changed it out and no problems after that, Magazines are a bit hard to find that actually work. If you use 20 rd aluminum Vietnam mags just load about 10 in there and it works OK. Very accurate. I wouldn't trust it to go into battle with but for playing around with it there's very little problems with it.
 
I've built several Ar uppers in 7.62x 39. The combo of the specific barrel and mags I use make them very reliable and quite accurate compared to most ak's. For a 16" build, carbine gas works great and a h2 buffer is about right with the size of the gas port in the barrels I use. I have around 5000 rds through one and 1 broken extractor is all that I have had fail. I use a kak bolt with an enhanced firing pin. The lower I use has an alg trigger with standard springs and it ignites all ammo without fail. Cleaning it every 750 rds or so keeps it humming right along and I run a lot of wolf steel through it. With wolf military classic 123 hp ammo it shoots honest 1-1/8" 5 shot groups. This Ar goes to the range with me almost every trip.
Cool and I was thinking about doing one in 762 and figured that the E-Lander mags would be great for it. Then I was thinking about the Faxon ARAK 21 and thought why spend $1100 on an upper
 

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