So I’m shooting 6.5 Grendel pretty exclusively (and darn expensively) and I’ve got my LMT upper and lower cerakoted now. The extra Troy MRF-R rail I have appears to be a good color match to the receivers. There is a new 25yd indoor rifle/pistol range opening up in a few months and 762x39 is about $0.25/rd here. So…a new barrel/bolt combo seems to be in order.
What I’m wondering is if anyone has ejection/function issues in the AR platform with 762x39. I think I can use the same grendel magazines for it…plenty of those, and can fireform/hydroform at a later date the brass for my AA 6.5G. This round might be used as a hunting round, but I’d rather use my grendel as it’s significantly faster and more accurate and the fact that I’ve got my leupy 4-12x40 zeroed on that weapon I’m going to leave the 762x39 for home defense. Suggestions? comments? All appreciated.
Not so sure you will be able to use your 6.5G mags. The taper on the 7.62 round is much more than the almost nonexistent taper on the Grendel case. I would think that the 7.62 case might bind when loaded to capacity.
I too have been interested in a 7.62x39mm AR15 style rifle and called PWS. I was told that there are issues getting mags to function with that cartridge. They tell me that there uppers are GTG but that the C-Products mags have problems. I’m quite sure they have tried all available mags and would have found out if the 6.5G was a solution. Apparently the 6.5G mag is not a solution to the 7.63x39mm AR15 style rifle feeding correctly.
I was ready to buy then and there but I was told by PWS that the C-Products mags are a “2 out of ten, good to bad ratio”. Wish there was better news. Maybe an owner of a 7.63x39mm AR15 style rifle can chime in?
I have two 7.62 ARs. The uppers like you said are GTG, they really shoot great if you do a quality build, the Bushmaster uppers aren’t half bad for the money as well. The big issue, as you mentioned, is the mags. The only decent mag on the market is the C Products, and the great to “throw that shit away” ratio is about 2-3 out of 10. If you can get your hands on a pile of mags and find which ones run, it can be a very successful platform. If you are interested I am actually selling one of my uppers with two working mags. The key is finding a set of mags that work, and keeping the gun reasonably clean.
I have a 20" M1Sales upper, and will be contacting Matt about his upper. My M1S upper came with 2 C-products mags, 10 rounders that hold 8 rounds. C-products seems to have a decent return policy, so I would see about buying as many as you want and testing them all, or buying more than you need, and seeing if you can send the ones that don’t work back. I still love the caliber in the gun, and I am looking for another one, if that tells you anything.
Sorry to hijack, but since this thread is titled “762x39 AR”, I had a few newbie questions. So do these uppers fit to the standard AR lowers? Do the 6.8 and 6.5 uppers also fit onto the standard AR lowers? I know that the .308 ARs have their own separate lowers.
I ordered a 7.62x39 16" carbine barrel and bolt today, and will begin re-assembly of the rifle when the products arrive. Trigger and hammer springs and some KNS Mod1 pins will be going into the lower as well. Also picked up 120rds of Fiocchi 123gr ammo for it and eventually those brass cases will be fireformed to accomodate Grendel rounds
Specs:
LMT upper and lower w/SOPMOD 6pos
ER Shaw 16’’ carbine barrel w/lo-profile gas block
Ergo pistol grip
ambi safety
YHM oversize takedown pins
KNS Mod1 pins
ambi sling attachment plate
Troy MRF-R floating rail system
Streamlight TLR-1 w/pressure pad
Tango Down VFG
Vortex Strikefire Red/Green dot lo-mount
Should be a fun shooter. Can’t wait to get it into the range.
So are the only components that are different the barrel and the bolt? I am assuming that the standard upper and BCG are used? Would there be a difference in the type of gas block or barrel nut?
Uwe1,
I received my barrel, gas tube, and bolt from M1S Friday morning. Went to work on it. Had to cut down the FSB to make it a lo-pro gas block and painted it. A golf tee is very handy for keeping the gas block off surfaces while you’re painting it. That took the majority of the time in assembly of the weapon. I kept my LMT carrier because it only had 200rds on it when it was a 5.56 gun. Simply put my 7.62x39 bolt in the weapon and got the barrel nut torqued to 40ftlbs, aligned the notches for gas tube, and reinstalled the gas block that was formerly a FSB. Pins made it easy.
Function testing the weapon proved I need a stronger hammer spring, or slightly more protruding firing pin, or both. I only found these tidbits of wisdom after having put all the components together. 12 failures to fire in 75rds. I have 10 CProd 30rd mags (loaded to 25) and the 3rd mag did have some failures to feed. first two fed flawlessly. I started the day with 1380rds of x39, shot 75/1260 of those 1987 Yugoslavian milsurp rounds and called it a day. $250/1260 at centerfire systems. JG Sales has the same stuff.
I have ordered a wolf extra power hammer spring, and will be testing the rifle with that later this week. If I can’t get it to fire 100% then an enhanced 76239 firing pin from M1S will be in order. I’ve also got a TangoDown QD VFG coming, a 9mm SMG Vortex (1/2x36 thread pitch to match the M1S barrel), and soon tax stamps will be in order
I’ll be posting pictures of the transformation as soon as I get everything else in. A nice pictorial of a weapon that was previously going to be 6.8’d----I even had the bolt. Just couldn’t pull the trigger on shooting ammo that was 20% less than my grendel. 76239 is 1/4 the cost of my grendel ammo and the brass will later be used in feeding my grendel.
So to resurrect this slightly waining thread I’ve just gotten back in from shooting this gun today, seeing disney on ice with my girlfriend and her daughter, and going to a friend’s house to watch my wildcats lose to west virginny. At least the day started good…
The weapon is near it’s final. I still want a Streamlight TLR-1s (strobe) and really want to find a VFG that accepts a Streamlight pressure pad. The Tango Down QD VFG didn’t fit the pressure pad, so a temporary grip-pod with a flat surface came into the picture. I hate the GP, but it’s the best i could come up with at the time.
I have my Vortex Strikefire red dot in it’s low-mount on here, and a Smith Vortex 9mm SMG flash hider. A Wolff extra power hammer spring resides in the lower, and the M1S 762x39 enhanced firing pin is in the BCG.
The rifle shoots very controllably. Rapid fire today at the range proved to be very controllable, and had 1 mag early on had a FTFeed, while another mag had the same during rapid fire. They are listed as 30rd mags, but in reality loading them to 25 produced excellent results. I’d probably hurt myself trying to get 28 in them. I have 15 of them as I picked up a good deal on them and will be going through them soon. Shot 5 today with zero failures to fire, 2 misfeeds, and this was with 1987 vintage yugoslavian milsurp ammo. Previous runs with the stock LMT firing pin and hammer spring showed unreliability to be way way way way way way BAD. Thank God (not algore) for the internet as researching proved fruitful and results to be exactly what I’d want my new LMT/M1S/Troy/CProd weapon to produce.
So now, enough about the system. Here’s the photos.
I am using the same buffer on my LMT lower that I had when it was a 5.56 gun. In thinking that you only need the bolt, magazine, and barrel I will say no…
If you’re wanting to make your AR15 a 7.62x39 rifle then these are the items I’d consider requirements to make it run reliably.
ER Shaw 7.62x39 barrel and FSB. Gas tube and roll pin needed as well
Model 1 Sales enhanced firing pin—slightly more protrusion from the bolt face to cause ignition of recessed primers
C Prod magazines with Wolff 5% springs—25rds of 123gr weights a whole lot more than 30rds of 75gr. Kinda expensive to add to each magazine although if you want reliability that you don’t have to worry about, get them.
Obviously a 7.62x39 bolt or a complete BCG from Jsesurplus.com or somewhere that stocks them
Wolff Extra power hammer spring in your lower receiver. It’ll send the hammer swinging into the firing pin with a little more authority.
I have had no extraction issues in the few hundred rounds I’ve run through the rifle since I built it. I also run it ridiculously wet, and as soon as I get my 762x39 pistol 10.5" built I’m sending the bolt and carrier to Robar to have them NP3 the BCG because I am using corrosive ammunition.
I cannot comment on other manufacturers uppers. I don’t doubt they’ll do fine. I just had my LMT upper and lower cerakoted and I had the bolt carrier and a rail system waiting for it, so why buy a new upper when all it took was a barrel and bolt…and enhanced firing pin…and extra power hammer spring…
Plus the benefit of shooting and collecting brass means i can neck down 762x39 brass to 6.5 grendel at a later time
Noooooo…semi auto only. This weapon is incapable of FA fire.
The day I built it I didn’t have the 7.62x39 enhanced firing pin. I had 12 FTFires in 75rds. The enhanced firing pin and extra power hammer spring fixed that. Thank you.
