Gents,

I recently posted some of this over in another section that doesn't get a lot of traffic.  So, I will repost the piston part here in hopes of getting more feedback.  Primary use of this carbine will be self defense.  Reliability and durability is prioritized over weight and precision.

I recently purchased an LMT MPR upper.  This upper will be going on an SBR lower.  I also have a Rugged Razor suppressor that I would like to use on the carbine.  I am debating whether to purchase an LMT 12 in piston system for the upper, or whether to try and use a DI barrel.  I have been leaning towards the piston, as I like the idea of adjusting the gas to keep pressure down in the system, and thus cut down on wear and tear.  I recently read a post where a guy broke a bolt in his Colt 6933 after less than 2000 rounds, mostly suppressed.  He attributed the early wear to suppressed usage.

I thought about perhaps purchasing a 14 inch DI barrel and cutting it down in hopes that it would have a smaller gas port then a standard 10.5 barrel.  Additionally, I could use the LMT enhanced BCG.  However, this seems to be introducing a lot of unknowns into the system.  I worry that reliability, especially unsuppressed may suffer.

I do not want to make an upper that is strictly for suppressed use.  The LMT piston seems like a good solution.  Yes, I have seen the IV8888 video where he breaks one.  For now lets keep that out of the discussion as I'm not sure that test is a good indicator of how the system will perform for my usage.

Would love to hear your thoughts.  Thanks.

I ran both, suppressed. I have posted as a reply before -look for my posts-. Only thing left is all DI. Learn from others mistakes.

<- Multiple SBR owner,. Including LMT MRP CQB SBRs in DI and piston.  Forget the piston, DI is the way to go.

ETA: don't want to beat a dead horse. If you can't find my replies/posts on it, Let me know. I'll update this thread once I'm on a computer and not the phone.

77Bronc is a LMT fan in general and runs a MRP. I’m sure he will chime in before too long and answer your questions as best he can. Good luck.

The new plugs (new being the last few years) have "fire" and the "supp" on the other side, which is a smaller hole, as opposed to the older ones that have "fire" and nothing on the other side.

Reliability issues when running suppressed or in general?  I haven't heard of reliability issues with the MRP piston in general.  If they exist I'd like to know.

Oh I remember that thread now.  I even posted in it.

Interesting that there was never follow up as to what LMT said in terms of a cause.

My 10.5" MRP utilizes a Gemtech SBC.  Works very well with the Geissele Super 42 also.

Thanks for the replies everyone.  I was hoping that the LMT MPR Piston would be a good alternative to the HK416 but the consensus is that it is just not.  Maybe I should have bought a LWRC or PWS instead.  

Guess I'm sticking with DI for now.

Nothing wrong with the piston barrel.  It is a great alternative to the HK.  However it is heavy,  as are all piston guns, and I think most people just prefer DI.  The piston guns will still get dirty with a suppressor.  I had a 12" but wanted something shorter and lighter.   I also didn't like how difficulty it was to remove the piston plug with some muzzle devices.

I'm not sure that's the consensus.  There are a couple reports of failures but as far as I can tell, they're rare and seem to always have abnormal circumstances associated with them (modifications, torture testing, etc.).  However, the point about it getting dirty when suppressed is a good one.  I guess it comes down to what you're looking to gain from the piston system.

The only thing I'm looking to gain with a piston system is gas mitigation while shooting suppressed, while maintaining unsuppressed reliability.  My main concern was premature wear to the bolt from shooting suppressed in a 10.5 in barrel.  My thought was that a piston system was the easy way to be able to cut down on the gas.  I'm under no illusions that the piston system will keep the gun clean while shooting suppressed.

Yes, that piston plug interference with the muzzle device has always concerned me.  Never was able to find a definitive guide as to what devices were troublesome.

Who knows, maybe the next time LMT offers a sale, I may pick up a piston.

@LettersFromEarth, thanks for the plug...

Yes I am a LMT fan, really well made rifles, and their pistons are no exception.  Fully understand that DI was the way Mr. Stoner designed it, but LMT has done the piston right.

My MRP CQB Piston is a 16".  The piston has a "Fire" or "SUPR" section on the gas block. Ironically my piston came from the factory with a "H" buffer.  Then I read that all LMT pistons ship with an H2 buffer.  I contacted LMT CS, and they sent me a H2, 2nd day shipping and it did make a difference.  Not a lot but I can tell.

Now that I am running suppressed, the buffers are starting to play a role in the function.  The recoil is not an issue, I want to protect the upper.  I have a XH buffer from Slash in my 762 OBR and I am going to try it in the LMT next week, as I just got my Dead Air Sandman S and it appears to have more back pressure than my Silencerco Omega.

As far as I am concerned, there is not a better piston than the LMT, I really like them,  I have shot others, but feel the LMT is superior.  I only have 1 piston and many DI MRPs and will be converting one of the uppers to a 12" piston for my DD SBR as an option.

As you noted in your original post, the LMT piston is not adjustable in the sense, only FIRE or SUPR

When I do go with a 12" piston, I will go with a H3 buffer.....I don't think you will go wrong.  The LMTs are built like a tank.  Note LMT also offers an enhanced bolt as an option.

Let me know if you have any more questions.

Richard

Thanks for all of the information Richard.  When I find a good deal on a 12 in piston set up I think I’ll give it a go.

I own a 12" MRP Piston SBR as well as several other 16" mid length DI MRP's. I exclusively shoot suppressed and the 12" piston is the softest recoiling of all of them. (Surefire Socom 300)

Never had an issue and it's without a doubt the first one I'd grab when ______ goes down.