I have narrowed my next AR down to an LMT CQB MRP. I have researched a lot about piston AR’s and have found a lot of pros and cons, but a lot more pros the cons. I understand that Piston AR’s run a lot cooler and cleaner, but there are also a lot more parts involved and they weigh a lot more. I have also read from some creditable sources that a DI AR is more accurate. Is this true? I know that LMT makes good stuff, so I’m sure I will be happy either way… I just don’t have any experience with piston AR’s and I just want to know if spending the extra money is really worth it.
Well you have the luxury of being able to own both and switch b/t the two with a torque wrench and 2 minutes of time.
Only you can really decide what you need…I can say that very, very few people need a piston AR. They will not shoot as smoothly, weigh a bit more, usually slightly less accurate, and overall generally unneeded when the D.I. AR’s run as well as they do currently.
I would recommend trying a MRP CQB D.I. option first, shoot it a bunch, train with it a bunch, and then revisit the piston question after you have learned the capabilities of the D.I. rifles. In the interim continue to research and read on here what members generally have to say about piston AR’s.
You would more than likely be happy with either option, however in time you will see that you didn’t need a piston in your AR and especially not one at the expense of having a heavier, less smooth, less accurate rifle vs. a D.I. one.
this forum is pro d.i, so dont expect a lot of support for your decision.
I suggest going to a store, with a range and testing a few ar’s before you buy.
I have used piston driven ARs, and to be honest, found them to be useless.
The piston system is great, if the weapon was originally designed to have a piston.
Having a piston in an AR makes as much sense as a DI AK…
However, if you are set on a piston driven rifle, you are best off going with the LMT, so that when you realize that you made a mistake getting the piston, you can easily pull the barrel and piston out and replace it with a DI barrel…
Heat & fouling will be the same just the distribution will change. Gas block gets hotter & dirtier with a so called “piston” system. If the piston & block get too fouled, it will affect functioning.
The original system has a piston. It’s the bolt and the carrier is the cylinder. What the so called “piston” system for the AR does is add a piston rod
The advantage to the original system is that when the piston & cylinder (the bolt & carrier) gets fouled enough to start slowing things down, a squirt of lube will loosen things up and get it going again. That won’t be so easy with the piston rod system. It may not be advisable. I know some piston rod/op rod system specifically warn against oiling the piston & cylinder as it could cause the oil to ignite explosively & cause damage.
Add to that the gas block will get hotter, a disadvantage when pushing your hand far forward on the handguard, the piston rod adds weight, cost and complexity to the AR you have to ask if there really is an advantage
There are actually very few to NO positives for a piston AR. The best piston AR EVER MADE is the HK 416. It has issues.
So the question you have to ask yourself is having a gun that is heavier, has more recoil, is less accurate, more expensive and has a lack of parts support better than a gun that doesn’t have any of these issues?
Not to call out piston AR fans, but I am willing to bet that not only do I shoot more rounds through my AR, but I do it in TRAINING CLASSES. To add insult to injury, I do it suppressed out of a 10.5 (and haven’t had a SINGLE malfunction in YEARS).
Ask yourself, what will a piston AR do for me that a DI gun is lacking in???
C4
Grant, did you mean pros
Thanks man. Brain was running faster than I can type.
C4
I’m starting to see a lot more piston uppers available on equipment exchanges here and on TOS. If you already have a DI that you like, maybe put a few $ in buying a piston upper. If you like it, deck it out. I have a pws mk114 that I really like but, it’s a plain jane colt 20" A2 that rides in the patrol car with me on every tour. Just food for thought.
I’ve considered this before starting my last build. Based on the feedback from my friends and our local board, the consensus was that there was not any advantage when talking about middy or rifle length systems. There may be some advantage when discussing carbines in that you can directly regulate your gas versus treating symptoms of the DI carbine. The carbine also creates more fouling on the BCG given the shorter system, so there may be some positive there. But as you can see from above, that’s probably not as big an issue. Simple fact is that piston weapons are not standardized, and most parts are proprietary.
I have both DI and piston AR’s. Since this is another AR purchase for you, I can only assume that your other AR’s are DI. Being that this forum is pro-DI, you will not hear much positive things about piston AR’s. I have LMT, LWRC, POF, Barrett & PWS piston AR’s. Out of all of them, and my DI AR’s, the most accurate by far is POF. I know I will probably get some bashing for this but in my hands, POF has shot the tightest groups at distance. You have nothing to lose. If it doesn’t work out for you, you can always sell it. JMHO.
O
Before my first buy I was considering a piston system. Here’s what drew me away:
-
The idea of a piston driven system being more reliable was tempting, but in an AR platform the DI has had decades to be refined and tweeked into something the piston driven system just hasn’t had the same time and attention to become.
-
As for pistons being cleaner: that carbon has to go somewhere. It’s just as dirty, just not in the same places. Also, from the other posts in this thread it sounds like the filth in those “other places” can actually have a greater effect on the performance of the rifle than if you just ran a dirty DI.
-
Going along with DI having more time to come into its own with ARs, think of the price and convienence of getting replacement parts and other neccessities for a DI vs a piston.
-
Having a slab of metal slosh around inside your rifle isn’t going to help your accuracy much…
I might be beating a dead horse here, but it helped me to see all the reasons consolidated like that.
I think it depends on how much money you have to start with. I also came here wanting a piston rifle. I don’t dislike them, but what changed my mind was money, as I don’t have an endless supply, and all of the piston rifles I wanted, were expensive and very expensive. BTW, LMT was the “expensive” and HK was the “very expensive”
What I found was that for a similar amount of money I could buy a basic rifle say LMT or Colt 6920 , sling, 1500 rounds of ammo and a decent light for about the same amount of money as the LMT piston. If you’re talking HK; add a fun train with ex-SEALs shooting class and maybe even a mid priced red dot. I don’t have a lot of money and a good DI rifle works for me. Not saying that’s what you should do, just trying to give you a monetary perspective. Ultimately if the piston rifle is what you want, that’s what you should get.
Thanks for all the help guys. I took your advice and went with the LMT MRP - DI. I figure that (as stated above) if I MUST go piston I can always get the kit… Just got it the other day and couldn’t be happier. The only thing that sucks about the AR is that its a California version (bullet button/10 round mags), that’s cause I live in San Diego… Anyway Thanks again!
Schweet!
BTW, I’m moving to SD at the end of December. Give me a shout if there are any nice places to shoot out there. Cheers
Nice choice. 
Very nice! I want one of those, but they are quite pricey.
Have you had a chance to shoot it yet?
Grant, did you mean slower
Yes I have. All I can say is :dance3: LMT’s are Tits! :dance3: mounted the TA01NSN on it, the MRP is pretty disco.
What the hell is that giant revolver on the left?:blink: