AR Piston Upper - Not a DI vs. Piston Question

**OH58D** · 12-12-18, 13:56

I have a dozen DI AR's (Colt and LMT) that I have been buying since 1988. I have an extra LMT lower that I would like to put some kind of Piston upper on and try that system out. I have no complaints at all with my DI experience, but I want to at least play around with the piston system which I have not experienced. I don't need anything special with interchangeable barrel or anything extremely high end. I just want a good basic piston upper with 16 inch barrel.

I have looked at the Adams Arms entry level piston upper online, and I have seen some of the POF offerings. For me this would be a learning experience to see how well the piston system works and compare it to what I know and like with my DI weapons.

Any advice would be appreciated.

**MistWolf** · 12-12-18, 14:43

If you want to try a good "piston" upper, get the HK. Probably the best one there is.

**georgeib** · 12-12-18, 15:47

Major, I would like to suggest that you consider an upper by Primary Weapons Systems. They are, as far as I know, the only company that uses a long stroke system for the AR. Uses less moving parts than any of the short stroke systems, made in Idaho by good people with first class customer support, and comes with an adjustable gas system. Much lighter weight than the HK to boot. Probably the most underrated premium AR manufacturer of which I'm aware.

I have no association with PWS beyond being a happy customer.

**SomeOtherGuy** · 12-12-18, 15:53

I've owned two of the Adams Arms midlength piston uppers. In each case I talked myself into buying it on sale. Each one worked fine in 2-3 range trips, each one had different recoil vs. a DI upper, and the second one needed an H2 buffer to be tolerable and was best with an H3 but was marginal in reliability and ejection with an H3. They are functional, and seemed to be made decently. I sold each one of them and obviously decided I didn't need a piston upper.

If you just want to play around I would go with PWS if you can (never had one, only going by design and reputation) or Adams Arms. I've used a friend's POF on several occasions and have not had any desire to buy one myself.

**ODgreenpizza** · 12-12-18, 17:16

I've had good luck with a basic adams arms middy. They tend to be less expensive and midway carries spare parts.

**militarymoron** · 12-12-18, 18:10

What about an LMT piston upper to go with the LMT lower? It's not 'higher end' than the receiver

https://lmtdefense.com/parts/mlcpu
Or, if you already have an LMT MRP, there's a pistol conversion kit for it.

**arptsprt** · 12-12-18, 17:12

Interesting. I was going to recommended the exact opposite. That you do NOT consider PWS.

I live in Idaho (formerly Boise) and I own a PWS. Had to have one. Several people I shoot with have one and had to have one as Idaho folk.

Most of us, including myself, have had nothing but trouble with our PWS piston systems. Mostly gas related issues. The overall consensus is the older units are better than the newer.

My first hand experience with their CS left little to be desired.

Mine is the .308 (Mk216) but the others in the group are 5.56.

My 2 cents.

Originally Posted by georgeib

Major, I would like to suggest that you consider an upper by Primary Weapons Systems. They are, as far as I know, the only company that uses a long stroke system for the AR. Uses less moving parts than any of the short stroke systems, made in Idaho by good people with first class customer support, and comes with an adjustable gas system. Much lighter weight than the HK to boot. Probably the most underrated premium AR manufacturer of which I'm aware.

I have no association with PWS beyond being a happy customer.

Sent from my iPhone using Tapatalk

**Iraqgunz** · 12-16-18, 13:43

I have heard of the same issues, to include a large agency that was using their stuff.

Originally Posted by pomyc

Interesting. I was going to recommended the exact opposite. That you do NOT consider PWS.

I live in Idaho (formerly Boise) and I own a PWS. Had to have one. Several people I shoot with have one and had to have one as Idaho folk.

Most of us, including myself, have had nothing but trouble with our PWS piston systems. Mostly gas related issues. The overall consensus is the older units are better than the newer.

My first hand experience with their CS left little to be desired.

Mine is the .308 (Mk216) but the others in the group are 5.56.

My 2 cents.

Sent from my iPhone using Tapatalk

**Mr.Fårikål** · 01-12-19, 01:34

Originally Posted by georgeib

PWS recommended cleaning interval for the gas system, involving the 30 second pulling of the handguard, is every 5000 rounds. Yep, 5000! So for all practical purposes, that's as close to "don't have to clean it" as you're ever going to get.

I understand preferring DI over piston, and reasons behind it. I only own a single piston AR, the PWS mk1 mod 2, among all my DI guns. But I do find it strange that you'd be so butt hurt about someone wanting a piston gun... No where did the OP solicit opinions as to whether he should or shouldn't get a piston upper, in fact he seems pretty clear that he wants to know WHICH one to get. This begs the question in my mind why you're so angry about this.

You don't like pistons? Great. Move on dude... It's really not that big a deal, is it?

Which PWS do you have? I have been looking at their Mk111 Mod 2 which looks really nice. Be perfect for attaching a can to.

Originally Posted by pomyc

Interesting. I was going to recommended the exact opposite. That you do NOT consider PWS.

I live in Idaho (formerly Boise) and I own a PWS. Had to have one. Several people I shoot with have one and had to have one as Idaho folk.

Most of us, including myself, have had nothing but trouble with our PWS piston systems. Mostly gas related issues. The overall consensus is the older units are better than the newer.

My first hand experience with their CS left little to be desired.

Mine is the .308 (Mk216) but the others in the group are 5.56.

My 2 cents.

Sent from my iPhone using Tapatalk

That is interesting, can you be more specific about issues and problems you encountered? What went wrong? What did you not like? How many rounds did you put through it? What did the CS do that wasn't to your satisfaction?

Not that GarandThumb is the last source on everything, but I appreciate his reviews. He did a great review on the PWS vs. HK 416 from his experience. He put a lot of rounds through his PWS and had great things to say about it.