I am not an AR guy, but I need your help

[Jessesky]

I’m more of a milsurp and historical collector, but I do like practical rifles. I know way too much about obsolete guns and bolt actions than I do AR’s. They “don’t do it” for me. I do own an AR I built, but only because every American should and it’s useful.

That is why I want to build a 7.62 AR-10. I’m set on a gas piston gun so it runs clean and cool. 20” upper. I’d like the budget to be on the less expensive side, around $1000.

Any recommendations on:
complete gas piston uppers
Gas piston conversion kits
BCG

Are AR-15 and AR-10 gas blocks and piston conversions interchangeable?

 

[ar-newbie]

As far as I have seen so far, no one has released an lr 308 / ar 10 platform 308 gas piston system to date. No , ar15 piston systems are not drop in parts for ar10 rifles.

Without getting into a pro / con argument regarding DI vs gas piston, Why do you need a piston setup?

 

[ar-newbie]

The bigger issue working against any type of gas piston system for "ar 10" rifles, they are not standardized like the ar15, there are armalite and dpms platforms, with dpms there is gen 1, and gen 2. Then you get into all the different gas system lengths etc... This presents an awful lot of different versions that would be needed. I just don't see a demand to make it worth all the development effort and money required to get products to market. Even those who have spent some time on this particular concept, have walked away from the idea.

The typical application for the ar10 platform tends to focus on accuracy and aimed shots vs cover fire. The more I think about this topic, the more it really gets down to DI vs gas piston. Hard to talk about it without getting down to the nitty gritty. Many simply see gas piston systems as needlessly adding parts and complexity to a rifle because DI is "dirty" and bad. The typical use of ar style 308 guns is accuracy, not amount of fire down range. Many see it as a simple matter of firing guns creates dirt in the system, regardless if DI or gas piston, it still gets dirty. Having a gas piston isn't going to gain you any benefit. Yes, if you fire enough ammunition rapidly in an ar10 style rifle it would be possible to cause a gas tube blowout, but who really does such a thing? That is the use case scenario for a light machine gun, which is designed from the beginning to spray a lot of lead down range in a short amount of time. There are existing guns out there specifically designed for that purpose.

 

[Rembrandt]

Adams Arms makes a .308 piston unit, but I don't think you're going to get one on a $1000 budget. I have a couple piston units and they are nice.

https://www.adamsarms.net/p1-rifle-308-16

 

[ar-newbie]

Adams Arms makes a .308 piston unit, but I don't think you're going to get one on a $1000 budget. I have a couple piston units and they are nice.

https://www.adamsarms.net/p1-rifle-308-16

Interesting, I was not aware that came out. I know they were discussing it some time ago, and I thought they too had walked away from the idea. It's still not a kit people can purchase and just drop into a different brand of ar10 though.

 

[Doc Samson]

The Ruger SR762 is gas piston but the barrel is too short and the price is way too long for OP's requirements...

 

[redneck2]

Many simply see gas piston systems as needlessly adding parts and complexity to a rifle because DI is "dirty" and bad.

Jeez. I never knew my AR was so bad. It’s a Varminter, been on multiple prairie dog hunts. It’s had maybe 3,000 rounds thru it and has never had the gas system cleaned. In fact, the rifle has only been cleaned a couple times.

I’d wager anyone a $100 bill that it can hit a fifty cent piece size target at 100 yards, Because I’ve done it many times. Maybe I should get rid of it for something more accurate or reliable

I did buy some cheap factory ammo for the last hunt. Don’t remember the brand, but it was filthy. Didn’t use very much of it. I can see how it could cause issues

 

[Robert]

On the different AR308 patterns:
The big two are DPMS and Armalite. The Armalite of today is not the same company that built the original AR 10.

The only difference in the Gen I and Gen II DPMS receivers is the height of the rail. Now I could be wrong but that's what I remember from when I built mine. The receivers are the big difference. The Armalite has a different radius at the rear than the DPMS. The uppers and lowers are not interchangeable. There other parts that are specific to one pattern or the other, but pick a pattern, stick with it and you will be fine.

LaRue and some of the other boutique makes have their own patterns too, but the DPMS and Armalite are the big two. And of those DPMS has the most following, though Armalite has gained ground in recent years.

 

[Llama Bob]

As far as I have seen so far, no one has released an lr 308 / ar 10 platform 308 gas piston system to date.

Isn't the LWRC REPR a piston AR-10?

It can be done, but I don't think it can be done for $1000.

 

[fpgt72]

Scratch both itches....get the gun the US got shafted out of a FAL.....budget does not fit, but it is a much better rifle.

 

[Jessesky]

The main reasons are the adjustability of the gas system so I can tune the action to my ammo, and I like my guns to run clean.

The price is somewhat flexible, but it was my impression from building an AR-15 that you can build a much nicer gun than the factory offerings for the same price. Seems to be s bit trickier with the AR-10.

To the FAL, I want one, but only for collection purposes, same reason I have my HK91. The AR-10 is supposed to be my new do all rifle.

 

[Llama Bob]

A piston AR-10 is too unusual to be much of a build candidate. The barrel, upper, and piston system are all going to be special. There's some other assembled options beyond LWRC - Ruger, Adam Arms. Maybe others I'm not thinking of. None are cheap - probably $2000 minimum.

 

[Llama Bob]

I should also mention that .308 ARs tend to be DMR platforms, and accuracy is generally better with DI. So the market for what you want it likely to remain somewhat limited.

 

[IndianaBoy]

I’m more of a milsurp and historical collector, but I do like practical rifles. I know way too much about obsolete guns and bolt actions than I do AR’s. They “don’t do it” for me. I do own an AR I built, but only because every American should and it’s useful.

That is why I want to build a 7.62 AR-10. I’m set on a gas piston gun so it runs clean and cool. 20” upper. I’d like the budget to be on the less expensive side, around $1000.

Any recommendations on:
complete gas piston uppers
Gas piston conversion kits
BCG

Are AR-15 and AR-10 gas blocks and piston conversions interchangeable?

There is a massive thread on AR15.com by an outfit called Henderson Defense that runs a machine gun rental range in Las Vegas. The firing schedule of their guns is harsher than any military unit. They shoot them until they keyhole and then they rebarrel them.

Every piston AR variant that they have fielded has failed, and at lower round counts than their DI guns.

If you want a piston driven modern 308, look into the SCAR 17. Not gonna happen for $1k. And those guns are not without some failures of their own. I have seen more than a few pictures of cracked bolt carriers.


The Stoner expanding gas design is a marvel of engineering. It eliminates off axis forces, and reduces weight. The amount of carbon that winds up inside the receiver and bolt carrier group is insignificant. I didn't realize to what degree this is true until I started shooting mine suppressed. The flow of gas back down the bore because of residual pressure inside the silencer is substantial, and the resultant carbon fouling is orders of magnitude worse than a standard AR. They still keep working for far more rounds than anyone will be carrying on their person.

The AR10 market is much smaller than the AR15 market. In terms of tiers/pricing, you have Palmetto State Armory, then you have DPMS and Armalite, then you have Lewis Machine and Tool, and then you have LaRue OBRs and POF, and other high end makers.

On the high end I would favor LaRue, but those are out of your budget. POF, I think offers a piston 308, but as others have opined, and I agree with, the piston is shoehorning and unneeded part onto a Stoner rifle. Frankly I think it is a testament to how good the original design was that it actually works with a shoehorned short stroke piston.

 

[IndianaBoy]

The main reasons are the adjustability of the gas system so I can tune the action to my ammo, and I like my guns to run clean.

The price is somewhat flexible, but it was my impression from building an AR-15 that you can build a much nicer gun than the factory offerings for the same price. Seems to be s bit trickier with the AR-10.

To the FAL, I want one, but only for collection purposes, same reason I have my HK91. The AR-10 is supposed to be my new do all rifle.

An adjustable gas block will give you far more flexibility to tune your rifle than a 2 or 3 setting piston rifle. Typically those rifles have a 'suppressed-standard-adverse' porting that might work well with your ammo or it might be over or under gassed. I favor click-detent adjustable gas blocks from JP rifles.

 

[IndianaBoy]

Scratch both itches....get the gun the US got shafted out of a FAL.....budget does not fit, but it is a much better rifle.

The FAL was an important rifle, and an enduring design. Like many rifles from that time period, adding an optic was an afterthought, and accuracy was good enough for a battle rifle, but you won't see one in use in any competitions where accuracy really matters.

 

[IndianaBoy]

Palmetto State Armory could get you into an AR-10 for under a grand, and you would have some shekels left over for that adjustable gas block, or ammo, or optics. I'm not going to claim that they are on the level of a LaRue or other top tier manufacturers. I have used quite a few of their barrels and bolt carrier groups in AR-15 builds, and I have been pleased with the results. They have uppers and lowers available right now for as low as $530 shipped. Frankly I'm having trouble coming up with a good reason why I don't have one in my shopping cart for that kind of price.

 

[Robert]

Scratch both itches....get the gun the US got shafted out of a FAL.....budget does not fit, but it is a much better rifle.

Much better than an AR 308? Better how? More accurate? No. More aftermarket support? No. More rugged? Eh, maybe.

I love my FAL but putting a scope on one is a PITA. They are field accurate, read 2-3 moa. They are damned dependable and will eat rocks, have great ergonomics, but they are overall a lesser rifle. Again, I love mine, it's one of my favorite rifles, but my ARs are just as dependable and far more accurate.

 

[Robert]

The main reasons are the adjustability of the gas system so I can tune the action to my ammo, and I like my guns to run clean.

Why? Chances are once you find a good accurate load you'll stick with it. It really won't matter if the gas system is adjustable if you never adjust it. An adjustable gas block is nice for a suppressor, but even that is not a requirement. And most are two position, suppressed and not.

As far as clean, the gas nut on my FAL gets way dirtier than my AR BCG. I have to use pliers to work the gas nut off due to the fouling after even a few hundred rounds. It gets filthy. My AR is way cleaner after the same number of rounds. Though different powders will account for some of that.

 

[someguy2800]

In my opinion a piston AR just moves the dirty part from inside the bolt where it’s easy to access and clean to under the handguard where you have to disassemble stuff to access and clean. Most of the carbon and junk blows out the ejection port anyway as that is where the expansion chamber vents. If it’s under the handguard it’s all going to be trapped in there. With a standard AR I don’t think any more of it ends up in the action than any other semi auto.

 

[Coal Dragger]

I’m more of a milsurp and historical collector, but I do like practical rifles. I know way too much about obsolete guns and bolt actions than I do AR’s. They “don’t do it” for me. I do own an AR I built, but only because every American should and it’s useful.

That is why I want to build a 7.62 AR-10. I’m set on a gas piston gun so it runs clean and cool. 20” upper. I’d like the budget to be on the less expensive side, around $1000.

Any recommendations on:
complete gas piston uppers
Gas piston conversion kits
BCG

Are AR-15 and AR-10 gas blocks and piston conversions interchangeable?

My recommendation is to not even bother.

There’s a reason 7.62mm NATO AR’s that actually work right, and do so consistently cost $4K.

You won’t even get close to that at $1K.

Piston conversions are totally overrated and unnecessary on AR’s, they just add weight and cost.

 

[Casefull]

To the OP. You have received some really good advice in this thread.

 

[Jessesky]

From what I’m hearing, Direct Impingement May even be better for a DMR-type rifle. I certainly know they are less expensive.

In that case, I’d be browsing for an upper in the $5-600 range.

I prefer to do the build myself than a buy a complete rifle like I did with the AR-15

 

[Robert]

You can absolutely build a reliable AR 308. Find an upper you like, buy it and then get a lower of the same pattern. Build it up with whatever parts you like and you will have a rifle that you want. Will it be less expensive than an off the rack rifle? Maybe, maybe not. But it is yours.

Aero Precision makes some outstanding kit.

 

[Jessesky]

A friend also brought something to my attention. A 6.5 Grendel upper for my current AR, which approaches .308 performance. Not a bad idea. Ammo availability would be of concern though. I’d want to be able to walk in any local shop and pick up a box. Any of you 6.5 Grendel guys have comments on that?