Building an AR15 in 7.62x39 SBR....

[texas skeeter]

What's a good barrel length in 7.62x39 for an AR15 SBR I want to suppress? Also which mags seem to work the best for the AR platform and the 7.62x39 round?

 

[itchin]

Get an ak or 300.

 

[Saltyag2010]

ASC and C Products mags

 

[texas skeeter]

Get an ak or 300.

I have 3 AK's and the 300 is .90 cents a rd to shoot. Where as 7.62x39 is at .22 cents a rd now....

 

[Saltyag2010]

I have 3 AK's and the 300 is .90 cents a rd to shoot. Where as 7.62x39 is at .22 cents a rd now....

An AR is modular. There are tons of people saying AR15s aren't made for the 7.62x39 rd. I say go for it. There are sponsors on this site that make 7.62x39 uppers. Why not try it? It might take some trial and error on mags or bolts but you can get bolts that have a warranty. Go for it. I've been curious about this same round in an AR but I want to own an Sks first.

edit- sponsors link - http://www.runnerrunnerguns.com/category_s/1854.htm
ask them if they'll change the barrel for a shorter barrel for you.

 

[texas skeeter]

I've read numerous threads on numerous forums all with good reviews on an AR15 in 7.62x39. A lot of the folks state they like the platform for better accuracy and optics mounting. Though I'm not sure how accurate it will be as an SBR. Iam still trying to find out what an ideal SBR length to go with. I've already purchased a bolt carrier with heavier firing pin etc made for the 7.62 round. I was going to build a 300, but again at .90 cents a pull, Iam going to try the 7.62 route first. I'll already have a can, so if I don't like it, maybe I'll go 300....

 

[Mike_from_Texas]

Good luck.

 

[rl96ss]

The Mk47 T is our entry level MUTANT designed to be a budget friendly offering, giving you the opportunity to upgrade as you see fit. The Mk47 T offers the modularity of the AR-15 giving you the opportunity to readily upgrade your trigger, pistol grip, and stock to your preference. The Mk47 T features all new mid-sized receivers based on our Mk3 platform carved from billet 7075-T6 aluminum. The Mk47 T was designed to harnesses the power and reliability of the 7.62x39 cartridge utilizing a robust bolt also based off our Mk3. The unique Mk47 lower receiver readily accepts all standard AK Magazines. Every rifle comes equipped with a 30rd AK PMAG and CMMG's lifetime quality guarantee.

Available January 2015

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CMMG Mk47 MUTANT T:


Caliber:*7.62x39mm

Barrel:*16.1" Medium Taper Profile 4140 SBN
.311 Groove Diameter, 6 Groove Rifling

Muzzle:*A2 compensator
Threaded 5/8-24

Hand Guard:*CMMG RKM15 KeyMod

Upper Receiver:*7075-T6 AL

Lower Receiver:*7075-T6 AL

Trigger:*CMMG Single Stage Mil-Spec Style

Furniture:*Mil-Spec 6-Position Collapsible Stock, A2 Pistol Grip

Weight:*7 pounds (unloaded)

Length:*32.75 inches (stock collapsed)

Magazine:*Magpul PMAG® 30 AK/AKM MOE®

MSRP:*$1,499.95

Just save your self the trouble and buy one of these. Reviews seem to be positive.

 

[ed308]

I would try Grendel mags since that round is very similar and based on the 7.62x39. Buy a spare bolt too. 7.62x39 bolts break frequently. Here's a good article and tuning a 7.62x39 AR to make it run...

[video]http://www.majorpandemic.com/2014/11/making-762-39-Work-Reliably-on-AR15.html[/video]

 

[ed308]

C Product and Pro mags usually work best for the 30 round mags. 10-15 round aren't usually a problem. Its the 30 round mags that seem to have feeding issues.

 

[Se7en62]

Get an ak or 300.

An AK has more of a story behind it, but a .300 BLK is not necessarily all it's cracked up to be. Just look at it's ballistics profile and you can see where it falls short. It's also costly to fire, as it requires more than just a barrel swap to work.

An AR is modular. There are tons of people saying AR15s aren't made for the 7.62x39 rd. I say go for it. There are sponsors on this site that make 7.62x39 uppers. Why not try it? It might take some trial and error on mags or bolts but you can get bolts that have a warranty. Go for it. I've been curious about this same round in an AR but I want to own an Sks first.

edit- sponsors link - 7.62x39mm
ask them if they'll change the barrel for a shorter barrel for you.

I think the reason a 7.62x39 is a bad choice in 2015 for any platform, is because the cartridge itself. It doesn't have anything to do with what platform the round is being thrown through, but rather what does matter is that the round has just outlived it's relative effective lifespan and more current rounds have surpassed it.

Personally, I think that unless you're an operator firing suppressed or you just don't care about over penatration, then a .300 BLK is a novelty round that's filling a VERY small niche at a high cost and a lot of guys have jumped on that bandwagon for no reason other than curiosity and keeping up with the Jones'. After all it's a .30cal, 200+gr round, with only about 500 ft./lbs muzzle energy that needs either a short gas system or a suppressor to cycle properly, as well as a barrel swap.

IF there was any reason to actually build an AR in anything but .223 or .308, I would suggest a Sharps 25-45. The 25-45 cycles with any AR15 .223/5.56 factory gas system and carrier group, as well as fits standard magazines. All you need is a Sharps 25-45 barrel. Rounds vary, but 87gr soft points are around $1.10 - $1.28/rd and they deliver much much better ballistics over a 7.62x39, 5.56, and .300 BLK, being perfectly designed for hunting. That 87gr bullet flies at 3,000fps and leaves the barrel with 1,700 ft/lbs of energy.

...in fact...a Sharp 25-45 AR build just jumped to the top of my list.

 

[Sugar Land]

This may be a dumb question but why would you build a gun that you know has problems running?

 

[Mexican_Hippie]

Wrong, all 300BO requires is a barrel. 557 bolt and mags are used.

Also you're comparing subsonics 300BO to supersonic Sharps rounds. The supersonic to supersonic comparison of energy is very close.

 

[Mike_from_Texas]

An AK has more of a story behind it, but a .300 BLK is not necessarily all it's cracked up to be. Just look at it's ballistics profile and you can see where it falls short. It's also costly to fire, as it requires more than just a barrel swap to work.



I think the reason a 7.62x39 is a bad choice in 2015 for any platform, is because the cartridge itself. It doesn't have anything to do with what platform the round is being thrown through, but rather what does matter is that the round has just outlived it's relative effective lifespan and more current rounds have surpassed it.

Personally, I think that unless you're an operator firing suppressed or you just don't care about over penatration, then a .300 BLK is a novelty round that's filling a VERY small niche at a high cost and a lot of guys have jumped on that bandwagon for no reason other than curiosity and keeping up with the Jones'. After all it's a .30cal, 200+gr round, with only about 500 ft./lbs muzzle energy that needs either a short gas system or a suppressor to cycle properly, as well as a barrel swap.

IF there was any reason to actually build an AR in anything but .223 or .308, I would suggest a Sharps 25-45. The 25-45 cycles with any AR15 .223/5.56 factory gas system and carrier group, as well as fits standard magazines. All you need is a Sharps 25-45 barrel. Rounds vary, but 87gr soft points are around $1.10 - $1.28/rd and they deliver much much better ballistics over a 7.62x39, 5.56, and .300 BLK, being perfectly designed for hunting. That 87gr bullet flies at 3,000fps and leaves the barrel with 1,700 ft/lbs of energy.

...in fact...a Sharp 25-45 AR build just jumped to the top of my list.

Your statement on 300 blackout is correct when shooting subsonic ammo but my 8" Noveske 300 blackout runs 110 grain Barnes bullets over 2200 fps and cycles just fine with it without a can.

 

[texas skeeter]

This may be a dumb question but why would you build a gun that you know has problems running?

How do I know it has problems running? I've never owned one. LOL I like the AR platform and was trying to put something together alternatively to the 5.56 rd. I have a few AR's in 5.56 and .308. I also have a few Ak's. I just wanted a new project that doesn't cost $1 a rd to shoot like the 300, and I can't stand SKS's. It's just like those "Guys" that put a full size scope on a rifle cartridge pistol, What the heck for?

 

[Sugar Land]

I stand corrected. For some reason I read others comments and came to that conclusion. Good luck.

 

[Mexican_Hippie]

300BO is cheap if you reload. If not, then yeah it can be pricey for what it is.

 

[texas skeeter]

Iam not set up for reloading yet. I have so many irons in the fire to include other hobbies. I feel when Iam ready for reloading I will study and learn the process. Reloading can be dangerous as some knuckleheads have proven. LOL How much on avg though does it cost per rd for the 300 to reload?

 

[Saltyag2010]

I'm still for it. Try it out and let us know

 

[Mexican_Hippie]

Well, it's 223 brass and 308 projectiles so pretty common.

My brass was once shot 556LC that was resized. I bought a lot of it ready to go for $0.10 a piece. That's a 1 time expense (or very infrequent). You could reuse your own 556 brass if you want to do the work.

Excluding the brass - I am in the $0.25 to $0.40 range depending on the bullets and load and sales. If you want expanding subsonics projectiles for hunting you're back up in the $1+ range but you can approximate their ballistics for practice and paper within that initial range.