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AR-15 in 7.62x39 questions...

Gatorgrizz27

Well-known member
Joined
May 20, 2020
Member Number
756
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874
I currently have 4 AR’s in 5.56, a .300 Blackout, and will be building a 6mm ARC at some point. I have an unused stripped upper and lower that has me itching to turn into something. Requirements are it does something my current ones don’t, and I don’t want to reload for another cartridge. This means 6.5 Grendel, 6.8 SPC, .204 Ruger, and .224 Valkyrie are out. I looked into the 9mm AR thing but ended up buying a CZ Scorpion instead.

I’ve had zero interest in 7.62x39 AR’s in the past since it’s almost identical to .300 Blackout which I can reload cheaply, and most of them have seemed to have issues. However, the current ammo shortage seems to be a pretty good reason to put one together, I have a decent stash of it on hand and only an SKS that eats it. I also don’t like AK’s enough to spend the current market price on one.

Doing a bit of research, it seems that the majority of the problems are related to magazines, rounds getting hung up on feed ramps, and needing a different firing pin and possibly hammer spring for Russian ammo. So buy decent mags (I don’t need it to use AK mags), grinding the M4 feed ramps into one groove, use a properly modified BCG, and you should be good to go.

Is that accurate or will one always be a “project”?

I found a 16” carbine gas non-bull barrel for $90. Toolcraft BCG seem to be a good choice but are sold out everywhere. If I can find a BCG I’ll probably start ordering stuff. I know it’s just the bolt that’s different, but with the firing pin mod as well I’d prefer to buy it as a complete assembly.
 
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I went with Midway's AR Stoner barrel and their magazines.

As of right now, it's just a collection of parts, so I can't give you much feedback on function.

Edit, I was wrong, I bought a bunch of Grendel parts around the same time, I was confusing my Grendel BCG with my 7.62x39 BCG. Grendel came from PSA and my 7.62x39 also came from Midway.

https://www.midwayusa.com/product/1018653446?pid=603909
 
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Well, I went ahead and ordered a 16” carbine gas length barrel, Windham Weaponry bolt, and firing pin. Planning to order some of the CPD 28 round mags. Will probably take me a bit to put together the rest of the parts as I have several other build going on, but if the thing sucks I’ll swap the barrel out for a .300 blackout.
 
bump/hijack
Strongly considering trying to pick up a KS47 in the near future. I don't reload, so having something I can actually buy ammunition for would be nice. I know a guy local to me who has one and I believe he screwed up the firing pin, but he was also trying to put as many rounds down range as fast as he could doing mag change drills, so I'm not sure his experience will mirror mine...
 
I have never had a problem with the one I built a few years ago off a older Olympic Arms upper with a 16" heavy barrel. You do all the things to it you already know about and it should be fine. I am running a heavy hammer spring, but did not have a issue with FTF before I installed it. I only use ASC magazines and prefer the 20 rounders because the 30's are too long. Its one of my favorite AR's, makes a great camp gun due to the extra punch of the heavier round over a 5.56.
IMG_20161114_132537925 (Medium).jpg
 
Well, for anyone interested I ended up going ahead and basically finishing the gun today, haven’t test fired it yet. Setup is as follows:

16” carbine gas length barrel (not sure of brand, was a gun broker special)
Windham Weaponry 7.62x39 bolt and enhanced firing pin
JP enterprises adjustable gas block
Mil-spec trigger
H2 buffer with Springo red (extra power) spring
Duramag 28 rounders

Think it should be a pretty solid rifle, will update when I can get it to the range, possibly Friday.

Leaning on buying a Vortex Strike Eagle 1-6 for it, even though I’ve never been a fan of their stuff.
 
55372CA2-81EB-4B91-805F-CA1162556D9B.jpeg


Function tested today, as the rumors state it wasn’t successful. :laughing:

First round loaded fine, fired fine, didn’t eject. Was to be expected since I’m running an adjustable gas block and it was only backed out one turn. Pulled the charging handle and it was stuck. No bueno. Had to mildly mortar the round out, backed out the gas block screw, and the same thing happened.

I’m fairly certain a significant part of the issue is the “Maxx Tech” ammo I grabbed two boxes of for function testing and getting it roughly sighted in rather than burning the stuff I have stocked. The Maxx Tech cannot be chambered by letting the bolt slide forward and pushing the forward assist, you have to let it slam home, and most of them require light mortaring to extract even before they are fired.

The couple boxes of brass cased stuff and the bulk steel cased I’ve got didn’t exhibit the same issues, so hopefully they will run fine. I may have a chamber on the tighter side, I don’t have a headspace gauge for it.
 
Maxx tech is trash. Their 9mm stuff is jammo matic garbage.
 
Good to hear, as I only bought two boxes. There had still been a bunch of Wolf and other brands of 7.62x39 on the shelves, which was part of the reason for this build. Since I had 800 rounds of Tula and only an SKS that eats it, figured it get this up and running and then grab more ammo. If it sucked I’ll swap the barrel out for a .300 Blackout. Had also entertained a 6.5 Grendel but that ammo is the unicorn of them all right now apparently.

It is sort of comical that there is ammo that much worse than Wolf/Tula out there. Design a gun to eat garbage ammo and it still won’t run it. :laughing:
 
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My cousin has a Daniel Defense rifle that groups best on Wolf HP 75 grain .223. That shit used to be cheap.
 
the wolf isn't terrible.
it's just dirty and underpowered compared to proper milsurp x39.
It always goes bangs for me.

my brother in law did a mutant lower after he built one on a regular lower and it never ran for shit, even with the fancy mags for it.
runs 100% with ak mags.

but it was a shit ton of money IIRC, and I have no idea why he even built the thing.
 
Aisin said:
My cousin has a Daniel Defense rifle that groups best on Wolf HP 75 grain .223. That shit used to be cheap.
Click to expand...

I bought a couple cases of that same ammo many years ago and it always works in any of my .223/5.56 rifles. My Mini-14 trunk rifle seems to be more accurate with it than other ammo.
 
We built an AR-stoner kit rifle out for my daughter to start deer hunting with (state rules are .25 or larger and 5rd mag limit for big game) and it seems decent. About 1/5 to 1/10 rounds fail to fire on wolf FMJ, wolf HP is 100%. Tiny mags are probably masking the much-mentioned feeding issues. I didn't get a special firing pin, did get the higher power hammer spring. The FTF FMJ rounds go into my AK and go bang just fine consistently there.
 
ScottRS said:
We built an AR-stoner kit rifle out for my daughter to start deer hunting with (state rules are .25 or larger and 5rd mag limit for big game) and it seems decent. About 1/5 to 1/10 rounds fail to fire on wolf FMJ, wolf HP is 100%. Tiny mags are probably masking the much-mentioned feeding issues. I didn't get a special firing pin, did get the higher power hammer spring. The FTF FMJ rounds go into my AK and go bang just fine consistently there.
Click to expand...

i did the firing pin, works on the hardest primers
 
Update, took it to the range again today. Without touching where I had the gas block set it ejected Federal brass cased fine, and would reset the hammer but not pick up a new round from the mag. I backed it out half a turn and it ran perfectly. I switched over to the Tula I have stockpiled and the first case got stuck ejecting. Backed the gas block screw out a bit more and it ran like a champ.

It feeds 100% from a full Duramag, even with rapid fire. I’ll consider this a success for now as this isn’t a gun I plan on trusting my life to. The purpose was a range toy that eats steel case and hopefully it will see some use hog hunting where you’re trying to put a dent in the population.
 
ScottRS said:
Which one specifically did you get? And is it OK in a 5.56 as well? The one in my 7.62 build appears to be just a standard 5.56 firing pin by semi-calibrated eyeball.
Click to expand...

yes it is good in an 5.56 as well, i well put it under the mic this weekend and we will see.
black rifle arms
it is a smig longer
 
djljeep said:
bump/hijack
Strongly considering trying to pick up a KS47 in the near future. I don't reload, so having something I can actually buy ammunition for would be nice. I know a guy local to me who has one and I believe he screwed up the firing pin, but he was also trying to put as many rounds down range as fast as he could doing mag change drills, so I'm not sure his experience will mirror mine...
Click to expand...
So fast forward to today - Gun store across the river from work had an Anderson 7.62x39 AM15 that is now on my desk for way too much money IMO.

Bought 40 round box of Tula with it for $24 with plenty on the shelf and an extra promag incase the stock one Fs up. Will post results at some point.
 
I'm considering an AR/AK for the next gun. I really like my PAP.

I really liked the old SIG 556R but they are far and fewish between and way $$ now.
 
AR-47, A Voyage of Discovery...:lmao: (aka: The board is slow again and everyone likes pictures...whatever...)

After reading quite a few AR47 builds and seeing some that worked and some that din't I decided I should give it a go. I already had a stripped upper and some spares, almost halfway there. Since this upper is for a dedicated (registered SBR) lower all I had to find was a suitable length barrel/flash hider, magazine, a few small parts and a 7.62x39 BCG (altogether less than $300 and, surprisingly, all in stock and on sale).

Concern #1 - The AR-47 BCG was listed as having an enhanced firing pin. Didn't know what that meant and couldn't find an adequate description. For anyone who also doesn't know: The part of the firing pin that protrudes from the bolt face, the pin diameter has been reduced in diameter about .01 further inwards to allow the pin to go deeper into the primer. Likewise, it appears the firing pin shoulder that stops against the rear of the bolt has been cut back the same amount. Otherwise it is just an AR15 firing pin. The carrier is just a carrier, the bolt face has been rebated for the x39 case, otherwise it "looks" a std bolt (unsure about the extractor). Now I know...
CIMG1203.JPG


CIMG1204.JPG



Concern #2 - The need for a stronger than mil-spec hammer spring. After I was done beating on it with a whiffle bat I tested it out. The SBR lower had a reduced power hammer spring to accommodate a CMMG dedicated .22LR upper. Not sure if it was necessary as I was trying a LOT of things to get the dedicated .22LR to run 100% (it's at 93.452% currently, finicky POS). I had also reduced the mass of the hammer by grinding a 1/4" of hammer spur off to see if that helped (didn't make a difference). This combination worked 100% for ANY 5.56 I shoved into it. Put the AR47 upper on, charged it, pulled the trigger and......... click, followed by deafening silence. I was running steel cased Wolf and the primers are, indeed, hard. The reduced power hammer spring and/or hammer mass didn't work. I borrowed another hammer and spring from a really cheap build and swapped 'em. Charged it, pulled the trigger and.... boom. However, the rearward travel of the bolt is pretty violent. The hammer spur was bouncing off of the rear of the disconnector and causing the hammer to not reset properly. Re-installed the ground down reduced mass hammer for the .22LR and everything was still fine... charge, squeeze, boom. Will it affect the .22LR upper? I didn't bring it to test :mad3:. And... I am also going to install a soft rubber Limbsaver pad on it, the Magpul pad (much like a Jeane Kirkpatrick doll) is made from the toughest, hardest, coldest plastic known to mankind. After 30+ rnds I was done.

Moral: a mil-spec hammer spring worked fine for me, consider a soft rubber stock pad instead...

CIMG1206.JPG


Concern #3 - Mag selection. From the intardnetz, no magazines worked properly or all of them functioned flawlessly, depends who was typing. I decided on a 10rnd Duramag simply because it was on sale and wasn't shaped weird. It worked like a charm, three refills (30 rnds :flipoff2:) with a brand new upper and not one FTF or FTE. Speaking of which, a standard mil-spec upper worked just fine, I wondered if an increased sized port was needed. Nope, didn't need an increased ejection port size like with my .45acp upper.


Of note: I reload 7.62x39 for my AKs. Turns out that my reloading recipe (21 gr of IMR4227, 123 SP bullet and std large primer) is not hot enough to cycle this AR47 (it will cycle all of my AK-47s 100% of the time, however). It short strokes and doesn't strip a round from the mag. 21 gr of 4227 is squarely in the middle of the Lyman Reloading Manual listed amount of this powder so I'm just going to increase the charge by a small percentage. Or, it might only get fed Wolf, who knows...

The only two other rnds I would like to chamber in this gun would be .357 Mag and/or .44 Mag (the other rounds I reload that I don't have an upper for).
CIMG1207.JPG


It's been raining here DAILY, I haven't tested the inherent accuracy yet to see if I did better than an AK (Krink-ish version) or not...:laughing:
 
I don't like Duramags, never had good luck with them. I bought 5 of them and none of them fit in my Mini-14 properly. Same for the 5 that I got for my M1-a. I had to force them to seat, so I sent them back.

I have a bunch of ASC mags for my 7.62x39 AR. All have worked perfectly for years. A buddy of mine who lives in a free state got his 5 pack 20 round order within a week of purchase a few months ago. The 20 rounder is my preferred size for this AR, the 30's are too long and heavy.

ASC | 7.62x39 Stainless Steel AR-15 Magazines

Ammunition Storage Components High Quality Stainless Steel AR-15 7.62x39 magazines
www.ammosc.com www.ammosc.com
 
Next credit card cycle I will get some ASC 20 rnd mags, for sure. As for a outfit that can't manufacture a magazine that even barely functions I stay away from anything ProMag (regardless of gun or chambering). Gambled on 10 rnd Duramag and got lucky... this time....
 
An update: With the mil-spec hammer spring in the lower (to accomodate the hard Russian primers) I have discovered that my dedicated CMMG .22LR upper runs about 97% now (3 FTF out of 100 rnds). Before I was lucky to get it to run 80%. I was trying a lot of things to increase reliability of the .22 upper on that particular lower, apparently a reduced power hammer spring was not a step in the correct direction. The three rounds that didn't chamber couldn't be forced into battery so I'm thinking the cartridges were the issue, not the gun. Maybe this will help someone.
 
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