7.62x39 Piston Rifle

[HeruMew]

16” 7.62x39 Short Stroke Piston System


A few months back, in the beginning of 2018, I traded an Optic I had for an Adams Arms Low Mass Bolt Carrier – Carbine Length Piston kit. I already owned an Adams Arms AA-15, I wasn't using the entry level optic (about 140 dollars) and decided that the swap would be a good one to, at the very least, have piston rod/block/spring replacements.

While sitting and mulling over what I should do with the expensive part of the kit: The Low Mass Carrier, I wasn't sure if I should run it in my AA-15, create a whole new build, or what. For a very long time, I had had interest in building out an Upper in 7.62x39. I know I didn't want to spend more than an Entry level AK, as, that would just be foolish in the long run economically.

For this rifle, I really just wanted an easy going plinker. I wasn't looking to build a fighting rifle, or competition gun. I really just wanted to finalize a full build of a stripped lower and upper. For the pride, joy, and success of putting in the efforts.

So, keeping in mind this is a budget rifle, I have the following companies Frankenstein'd into this rifle:

Upper:
Stripped BCM Upper w/ Dust Cover and Forward Assist - $65.00
Bear Creek Arsenal 16” 7.62x39 Barrel .093 Gasport - $75.00
Bear Creek Arsenal MPI/Headspaced Assembled Bolt - $45.00
Adams Arms Low Mass BCG and Adjustable Gas Block - $140.00
Adams Arms Handguard - $0.00 (Takeoff from another rifle when I swapped my 5.56 to a MOE SL)
Cost of Upper: $325.00

Lower:
Anderson Lower - $40.00
Stag Arms Parts Kit w/ FCG - $32.00
K-Grip - $14.00
VLTOR A5 Tube / A5-H3 Buffer - $40.00 (Thanks to a great member here in the Equipment Exchange)
Cost of Lower: $126.00

Total Cost: $451.00

Overall, I stayed under the 5-6 hundred dollar budget that I know an AK would be at; I also had a lot of these items for months and months.

I had the sight I traded back in January since 2015. I have had 4 Anderson Lowers bought back in 2016, from a member here on the Exchange, again a very good deal. I still have 2 fully built lowers without uppers. The Stag Arms Parts I picked up during Black Friday as they had an amazing deal.

The rail is the hard part. I had hoped one I had would work, but not currently. I have a round handguard cap that I had to modify to accept the piston. Than I can add my own standard carbine guards or try the BCM PKMRs (I tried it, they don't work. Good news is, my pistol just got a new set of PKMRs on it). One of the biggest detriments to the Adams Arms Kit is the handguard compatibility. It only can utilize Samson free float guards or only about 50% of handguards that are “drop-in” and still use a standard barrel nut.

The BCM upper should speak for itself, but I must say, the Bear Creek Arsenal extension was sized as if it was built for the BCM upper. It was a super snug fit, but not one I needed a mallet or heat gun for. A light pressure and some wiggling and it pressure fit in very nicely. I have a relative with a truing stone for the upper and after running the truing through, it was an immaculate fit.

I picked up two different magazines for the rifle:
1x ASC 20 Round Magazine
4x C-Products 30 Round Magazine

I tested both magazines with single rounds, multiple rounds, and full.
We had Bolt Hold Open success with all of them.

The mags drop free very well, except the ASC. Overall, I am not too worried about it.

When we talk about the gas system / BCG, this is what really sold me on the 7.62x39 build. The research I read, across multiple sources, insisted the 7.62x39 round is “low pressure” in comparison to the .223/5.56. When I heard about this, and the problems it comes with, I did some digging. I noticed that many were having difficulties with springs being too powerful, or the mass being too high for reliable extraction and stroking. When I saw that low mass carriers were a big help in tuning these rifles, I knew I was interested and in the right direction.

I am, supposedly, supposed to be receiving an adjustable gas block from Adam Arms any day now. They reported issues with the XLP gas blocks seizing up. They advised me they would send out a replacement block in honor of warranty. I threw this one on to test operation, to see if the gas was ported well enough for the standard piston gas block. It sure is.

It runs very well so far. I have put a couple hundred through it, and the most notable piece is the impulse being extremely different. I have not had any hiccups due to weak springs / hard primers. Keeping my fingers crossed.

Nonetheless, this build has been a crazy adventure. I will post my build photos below and will post up a video of operation soon. Thanks for all your time and energies reading this build.

http://image.ibb.co/iKMLXH/S0412154.jpg
http://image.ibb.co/h9HAXH/S0422155.jpg
http://image.ibb.co/jrk8Kx/S0442162.jpg
http://image.ibb.co/ccjw6c/S0452164.jpg
http://image.ibb.co/iLukzx/S0462166.jpg

[docsherm]

What are you going to do for sights?

[HeruMew]

Some sort of red dot.

Already sighted in a really cheap dot to do my test firing. But took it off to avoid a beating on the cheapo optic.

Not sure exactly what, but something around the 2moa size is what I am thinking.

ETA: I am also going to be running to Menards or Home Depot this weekend to pick up an auto punch to finish off staking the castle nut.

[sasquatchoslav]

I love everything about this, but snow in the pictures? Ya gotta put up a warning I'm allergic to snow!

[HeruMew]

I love everything about this, but snow in the pictures? Ya gotta put up a warning I'm allergic to snow!

Haha!

Yep, still got that stuff for another couple weeks, at the very least. We got another batch coming on Monday.

At least we'll hit the forties again next week.

[sasquatchoslav]

At least we'll hit the forties again next week.

Ouch.

Currently out in a field prepping a food plot for deer in shorts and a t-shirt low 80's. Sorry had to rub it in;)

Enjoy the new rifle my 7.62x39 is leaning up against a fence post 5' from me ready for coyotes. It's earned the top spot as my go to rifle for all things on 4 legs year around.

[HeruMew]

Ouch.

Currently out in a field prepping a food plot for deer in shorts and a t-shirt low 80's. Sorry had to rub it in;)

Enjoy the new rifle my 7.62x39 is leaning up against a fence post 5' from me ready for coyotes. It's earned the top spot as my go to rifle for all things on 4 legs year around.

We had another group of 'Yotes hit the back acreage up here, but they haven't come in for a good shot.

We have chickens, about 10 of them, so we get a few every year from the rough acres trying to slink their way to check out the coop. So, if they leave our livestock alone, we leave them alone.

If this rifle gives me the accuracy I am hoping for, I am certainly considering taking a deer with this rifle this year.

[sasquatchoslav]

We had another group of 'Yotes hit the back acreage up here, but they haven't come in for a good shot.

We have chickens, about 10 of them, so we get a few every year from the rough acres trying to slink their way to check out the coop. So, if they leave our livestock alone, we leave them alone.

If this rifle gives me the accuracy I am hoping for, I am certainly considering taking a deer with this rifle this year.

It seems like the more coyotes we kill the faster they breed they are about as bad as hogs. It's unreal when the calves drop they are like a locust plague

[rpoL98]

nice build.

[RobertTheTexan]

This is the second 7.62x39 AR I’ve read this morning. I almost think it would be a sigjn, îbut I haven’t felt called to dabble in that direction. Part of me wants to get my own rivet machine and whacked else and build some AK’s. I do have a couple of questions.
1. When you get a hand guard on it, will you mount some buis? Or replace the GB with FSP? I know you said it’s not a fighting gun, but still, no matter the budget I always run back up irons. I know there are some guys who have more expertise than me who don’t use them at all - but that’s not my camp.
2. How is the BCA barrel working out? Do you have any expectations for accuracy? I see them advertised at Primary Arms - and I know they are made here in the states, but beyond that I’m not super familiar. I know I’ve been hesitant to buy primarily because I just can’t believe a good barrel can be had for $49 bucks sometimes free w/ a BCG purchase. Being a. “You get what you pay for” kind of guy, I’m really left wondering how good they really are. Looking forward to your input.
But overall I really like that you stepped outside the box and brought us something really different but with a defined purpose!


Sent from my iPhone using Tapatalk

[pinzgauer]

It seems like the more coyotes we kill the faster they breed they are about as bad as hogs. It's unreal when the calves drop they are like a locust plagueYou do know that is exactly what happens, don't you?

Stable groups have low birth rate. Loss of even one pack member will trigger them to come back into estrus and increase their birth rate.

And that awful hyena sounding warbling is part of how they know a member is gone.

Get a watch donkey or herd dog. That's about the only thing that works.

[HeruMew]

We had another group of 'Yotes hit the back acreage up here, but they haven't come in for a good shot.

We have chickens, about 10 of them, so we get a few every year from the rough acres trying to slink their way to check out the coop. So, if they leave our livestock alone, we leave them alone.

If this rifle gives me the accuracy I am hoping for, I am certainly considering taking a deer with this rifle this year.

I jinxed it, truly...

Last night, lost our Rooster to a 'Yote attack. It happened fast, but either he was the most pleasing looking, or he put up enough of a fight to be the one taken.

I know if I hit em back harder, they'll probably just expand the pack. But, I want my $7.00 in pelts at this point for the cost of my damn Rooster.

Anyways, It happened so quickly, our dog (inside but only 30 feet away) didn't even bark. My wife swore she heard it, but they're loud animals and just went back to bed.

Damnit. At a crossroads now. Pinzgauer makes a good point about them just coming back with bigger packs. I would just hope to drive em off to the next spot. We have roaming dogs, everything. But, they got confident last night. Happened around 2AM.

I truly, cannot believe though, that I jinxed it with this thread. In four years, 20 chickens, we never lost one to a 'Yote. And all that changed last night.

[HeruMew]

This is the second 7.62x39 AR I’ve read this morning. I almost think it would be a sigjn, îbut I haven’t felt called to dabble in that direction. Part of me wants to get my own rivet machine and whacked else and build some AK’s. I do have a couple of questions.
1. When you get a hand guard on it, will you mount some buis? Or replace the GB with FSP? I know you said it’s not a fighting gun, but still, no matter the budget I always run back up irons. I know there are some guys who have more expertise than me who don’t use them at all - but that’s not my camp.
2. How is the BCA barrel working out? Do you have any expectations for accuracy? I see them advertised at Primary Arms - and I know they are made here in the states, but beyond that I’m not super familiar. I know I’ve been hesitant to buy primarily because I just can’t believe a good barrel can be had for $49 bucks sometimes free w/ a BCG purchase. Being a. “You get what you pay for” kind of guy, I’m really left wondering how good they really are. Looking forward to your input.
But overall I really like that you stepped outside the box and brought us something really different but with a defined purpose!


Sent from my iPhone using Tapatalk

Thanks for the great questions and comments!

Question 1: At the moment, my only option for a decent free floated rail will be a Samson rail. I see them for around 100 bucks at places. But, to be honest, I am not sure how much more cash I will throw into this one. While I am a true believer of FSPs, I have them on every other AR I own at the moment, this handguard was free (well, a takeoff from an old Adams Arms Rilfe), allowed me to utilize this piston system, and kept the build moving. But, I am not the most advocating for RDS-Only guns. It will probably bug me enough to change one day, but in the meantime, I will just shrug it off.

If I do end up with some extra cash in hand after I finish the midlength I am building, I may get a Samson and call it a day. If I do so, I will defenitely be putting some buis on it. Probably MBUIS, due to cost and rifle use.

ETA: I wanted to mention: I won't be able to switch to a FSP, due to the piston system. Unless Syrac or Adams Arms offers an FSP Piston Gas block. Which, oddly enough, would be bad ass if they did.

Question 2:
BCA "Guarantees 1MOA at 100yards with proper ammo and shooting technique".

My home range is only 50 yards, max. But, I am also in the midst of rebuilding my target stand much better. (Going to use 4x4 posts and 2x4 brackets so I can quickly swap out plates for a blank 2x4 for paper targets.) Otherwise, I would go setup my caldwell and at least see what it gives me at 50 yards on a target and upload it. Of course, per Minnesnowta, after I pulled up the old shot out stand, the ground is still too frozen to dig to put some concrete footed 4x4s.

It seems quite accurate thus far, but I don't feel comfortable saying it lives up to it's advisement until I get some real bench rested, 5-10 shot groups, at a true 100 yards.

It runs great so far, I have put about 500 through it so far (mostly popping clay pigeons on the ground while my stand is effed), we'll get some real accuracy info soon.

[sasquatchoslav]

You do know that is exactly what happens, don't you?

Stable groups have low birth rate. Loss of even one pack member will trigger them to come back into estrus and increase their birth rate.

And that awful hyena sounding warbling is part of how they know a member is gone.

Get a watch donkey or herd dog. That's about the only thing that works.

It's an interesting if not frustrating situation. ~3000 head on 18k acres the operation gets bigger every year. Hunting lease on 8k of that, but they don't care about the fawns we lose that's for us to take care of. The trappers do a big push rihgt b/f the calves drop for the ranchers, but the rest of the year they go wild and just crush the fawn population it's super frustrating. It's costs $200/day for a trapper and our lease is expensive enough already so we just do what we can when we are there. QDMA told us the best option is to do our own trap push right b/f the fawns drop and then hunt our butts off the rest of the year. Oddly no one has brought up a donkey or dog to patrol the land I will ask the main cowpoke what he thinks about that. I can't imagine stopping the coyote hunting will lead to less fawn loss, but if that's they case I'd love to see some data behind it on a property with solid professional deer management and if it works I'm sold. I don't know if they would allow us to bring our own animals in either that would be another conversation all together.

[Buckaroo]

Worked on a good sized ranch running both cattle and sheep. We hunted year round and brought in trappers frequently. IIRC I saw two yotes on the ranch in 4 years. One calf had a haunch chewed up pretty badly but survived.
We hunted by fixed wing 5-6 days a week. Killed many far and wide as we had to permission to hunt. We also ran up to 2 dozen Great Pyrenees dogs that stayed with the sheep. I'd never seen dog food bought by the ton before lol. Filled dog feeders when we ran salt and mineral every week.
There are ways to keep the population down in an area but there is a price to pay.

Sent from my Pixel using Tapatalk

[sasquatchoslav]

Worked on a good sized ranch running both cattle and sheep. We hunted year round and brought in trappers frequently. IIRC I saw two yotes on the ranch in 4 years. One calf had a haunch chewed up pretty badly but survived.
We hunted by fixed wing 5-6 days a week. Killed many far and wide as we had to permission to hunt. We also ran up to 2 dozen Great Pyrenees dogs that stayed with the sheep. I'd never seen dog food bought by the ton before lol. Filled dog feeders when we ran salt and mineral every week.
There are ways to keep the population down in an area but there is a price to pay.

Sent from my Pixel using Tapatalk

That's the approach we are taking trap + hunt. The hunters did a couple of focused traps b/f fawns dropped last year, ranchers did their own periodic trapping for the calves in winter and we hunt them hard year around as do the ranch hands.

[HeruMew]

Just got an email from Adams Arms.

They've sent me the invoice for my warranty item and I should be receiving it sometime soon.

I didn't realize they had been back ordered, it was taking a little bit to get a response (about 20+ days since I was advised it would be replaced) but if they really where that backed up, it makes sense. I get it.

They're taking care of me, should have the adjustable one mounted soon. Very satisfied with the level of service the company provided. Certainly A++ For having nearly $1k invested in their products since my 21st Birthday.

[RobertTheTexan]

It's an interesting if not frustrating situation. ~3000 head on 18k acres the operation gets bigger every year. Hunting lease on 8k of that, but they don't care about the fawns we lose that's for us to take care of. The trappers do a big push rihgt b/f the calves drop for the ranchers, but the rest of the year they go wild and just crush the fawn population it's super frustrating. It's costs $200/day for a trapper and our lease is expensive enough already so we just do what we can when we are there. QDMA told us the best option is to do our own trap push right b/f the fawns drop and then hunt our butts off the rest of the year. Oddly no one has brought up a donkey or dog to patrol the land I will ask the main cowpoke what he thinks about that. I can't imagine stopping the coyote hunting will lead to less fawn loss, but if that's they case I'd love to see some data behind it on a property with solid professional deer management and if it works I'm sold. I don't know if they would allow us to bring our own animals in either that would be another conversation all together.

I see donkeys used a lot. Seems like every sheep / goat ranch I’ve seen a from East Texas to Central Texas. They work, although I’m not sure what the ratio is, if there is one. Sounds like I need to throw a couple guns in the truck and drive out to Fl.

[HeruMew]

Just got the Adjustable Block.

Will be swapping it out and tuning it to my lightest load in the coming weeks.

[rpoL98]

I'd be interested in knowing whether the 74% (or lesser) position still gives you last round bolt hold open. Keep us posted! thanks!

[HeruMew]

I'd be interested in knowing whether the 74% (or lesser) position still gives you last round bolt hold open. Keep us posted! thanks!

You betcha!

Leaving this AM for a Gun Rally at the Capitol. Hope I can find time tomorrow in this chaotic weekend.