On the whole, I’ve seen less POFs running correctly than I’ve seen with issues.

OK I will qualify that. I already said it once but I will again.  Recoil impulse with a Sig, LMT piston gun suppressed slows things down (rate of fire) which in turn causes the rifle to shoot softer.  DI on full auto suppressed changes the rate of fire considerably (more recoil). Piston runs cleaner with suppressor and less gas to face especially for us lefties.  I have many DI's and is my first choice unless running suppressed.

LMT is one of the top weapons out there.  If you have to be convinced to get one then you probably won't.  LMT builds combat guns plane and simple. Hardcore war guns.   I don't know a lot about the guns you mentioned.  I have heard good and bad about them but I don't have experience with them.

A piston gun does not inherently reduce the rate of fire unless there is a suppressor setting on the gas block.

You can accomplish the same thing in a DI AR15 with buffer tuning and an adjustable gas block.  You can also accomplish the same thing with an appropriately sized gas port.

Pistons don't run cleaner.  They're just as dirty as a DI AR15.  Unless you're running a low back pressure, flow through can, the majority of contaminates are coming back through the barrel, not the gas tube.

Pistons work better than DI gun's in very short barrel applications due to the violent nature of the piston operation.

My 12.5 inch LMT piston does not shoot softer than my 10.5, 11.5 or 12.5 inch DI barrels.  Period.

If your LE/MIL you can access Proven Arms & Outfitters for availability on some sweet items. I just picked up a SIG516G2 from them.

https://www.provenoutfitters.com/sig516g2-patrol-

https://www.provenoutfitters.com/sig-wrmcx-14b-tap-sbr

You could always go this route and add the shorter barrel later.
https://www.guns.com/firearms/rifles/semi-auto/sig-sauer-mcx-223-remington-semi-auto-30-rounds-16-barrel-new?p=61108

I actually just bought a used LMT upper off of Gunbroker.  Have put all of 50 rounds through it, so I can't really speak to it's long term reliability/durability.   I have owned my POF 415 and PWS upper for at least 15 years.  Both have thousands of rounds through them.  Not sure I've ever experience a jam with either.  Ran the PWS in a two day carbine class about 15 years ago.  Probably 6-700 rounds over the course of two days.  It rained the entire time.  My memory is that by the end of it both me and the gun were soaked and covered in sand/dirt.  Gun ran like a champ.  Being a civilian those are probably the worst conditions I'm ever going to run a rifle in.  I realize that for some military guys that would just be another day at the office.  But for me, I don't really need a gun that can stand up to more abuse than that.

I will admit, being able to swap out barrels and move from piston to DI is a nice feature of LMT.  Looking forward to putting my upper through its paces and see how it holds up.

Strangely my experience has been the opposite.

My newly purchased 12.5 LMT Piston is smoother then my 10.5 DI LMT.  It runs and feels like a sewing machine.  Maybe it's the Spikes Tactical ST-T2 buffer.  Maybe it's the newer Piston setup from LMT; which is similar to what they created for the Estonia contract (allows for the piston to be services even with larger muzzle devices attached).

Oh... and I can confirm that my LMT Piston runs CLEANER then my LMT DI (both unsuppressed).

Yeah, LMT is one of few companies piston that is actually being sold to militaries. Matter of fact LMT is probably the only one that is outfitting entire armies with their rifles both piston and internal piston.

POF is a great rifle. I think the founder died recently from a car accident so I don't know if their stuff is the same as it was. I don't think you'll see anymore innovations or at least ones that work.

Between all of the ones listed I really like the POF P415 and the LMT. I think they are great. The PWS is great but I don't like how the carrier looks. Looks really silly.

The LMT is the cleanest, in my opinion, and one of the easiest shooter there is. The PWS is great too but it is bulky and big.

FYI - The LMT Estonia Reference Rifle is currently on sale at Primary Arms for $2900 and code SAVE12 brings it down to $2552. I'm passing on this since tax to TX and already have an LMT rifle, but would be tempted otherwise.

LMT Estonia Reference Rifle

I own couple of different Sig's carbines and neither impressed me much, each with some issues and not perfect. Currently I own two different piston driven LWRC carbines and that is excellent firearms in compare. LMT and HK is tough to get and expensive but I am looking to buy LMT one day. HK is out of question, company don't like to sell rifles to US civilian market because of lot of shootings, means HK is totally under liberals in control. I think for the money and quality of product - LWRC will serve as well as HK anyway or even better.

2 things.
1. What was the issues with your Sigs?  Which model Sigs?  

2. HK won't sell to civilians because of shootings?   I've never heard that. Can you list a source for that one?   Thanks

1. Sig 556xi, piston driven right? Over-gassing right from the factory, no support after couple of years, no parts. MPX - still own it but not impressed with the accuracy, can get better results with $300 Keltek Sub2000, M400 - parody not an AR, jamming and with cheap black barrels. Also any civilian market rifles are with cheap non HF/CL barrels. They are hiding this info in specs.

2. That is known statements been explained many times, they are OK with pistols sale but not civilian carbines or "assault looking rifles" as they are saying. My guess after CT shootings and whatever happened to the Bushmaster etc. Current occasional sale of mr223 on Gunbroker is a nonsence in terms of price. Whatever they are selling doesn't look like AR it looks like guns for CA or NY, it is joke without even muzzle device. Totally under European liberals control, besides they can't compete here and they know this.

Sig 556 wasn't even in the discussion.  MPX is a 9mm so don't compare it to a 516 (you did)

you made the statement that HK doesn't sell to civilians because of past shooting but then say it was just a guess  (not a factual statement). In other words BS.

you are completely full of shit..

^ Are you one of these die hard Sig lovers? Be happy with what you have kid but don't forget, much better rifles are around.

Really liked the MK111 Mod 1 upper I had can’t speak on the others


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All listed are great guns. Occasionally you do see the 516 for cheap - like $600 or less. So if you want to build it on a budget this is the only real option.

Not at all a die hard.  More of a colt guy but you tried to come on here and bullshit.  I called your bullshit out.  Don't come on here and straight up lie.  Be above that crap. Nobody likes liars

I agree with you.  For the price you can find a 516 upper for, they are a great upper to assemble a gun from.

Not everything in your life what you possibly don't like is lie my son, again before accusing anyone you should have facts, I do and you don't. You sound more like a moron or something.

I have owned lots of piston ARs.  I would take a look at the HK option.

Before anyone buys a piston AR I would suggest they analyze why.  If you’re going to run a suppressed SBR I understand.  Otherwise, I’d just buy a DI.

Not your son.  You got caught up in your bullshit and got called out.  Done

I disagree with you.  Something different is ok. Yes running a suppressor is a big plus for a piston gun. Piston guns are cool in their own right.  I like both.  Hats off to someone who wants to roll a piston. Great system.  I have a Colt Piston, Sig 516, LMT Piston.  I have quite a few DI's and I like the pistons just as much.  A little heavier though as everyone knows.  AR isn't the end all be all.

Which one?  They are real pricey.  Badass though.

lol  "top Dog" extruded 6061 is not top dog material , don't believe the marketing, they do function,however, I have a long term tester that is way outclassed buy  it's LMT counterpart.

LMT doesn't make a gun like the MCX. Brownells is about the closest you will find with the 180.  I have an MCX and an LMT piston.  2 completely different systems.

I’d look at some folding options without the buffer tube. I’ll soon be doing a comparison video of the best side charging, folding brace, AR mag taking 8-12 inch guns as soon as the JAKL and P556 arrive to take on the BRN180S, 10.5” FM-15, 8” Galil Ace and 11” Bren 2.

It would seem quite possible that every firearm created has had issues in some way shape or form. Whether they were wide spread, indicative of a major design flaw, or just a manufacturing or quality control screw up, is another debatable story in it self.

Has it stands, the MCX is one of the premier piston platforms on the market. Does better exist, quite possibly but what is better and what your desired use for the gun is all debatable. Right now the MCX familiy innovation has been leading/pioneering the way.

The 516G2 Upper Receiver Assembly or the complete rifle is one of the best piston AR's and it is possibly the best bang for your buck in the Piston AR category.

In regards to the MPX, all I hear is get one. User feedback is generally positive regardless of issues.

Understandably it is always very disappointing receiving bad apples especially from SIG. I too have had issues but SIG quickly remedied them.

By stating the above I am not stating anything negative about LWRC, LMT, H&K, Caracal, Haenel, etc.... I'm sure there are plenty of owners who do prefer brand X over brand Y, regardless of which is better.



One thing to point out regardless of how people feel about SIG is that they do sit atop the hill with the other big dogs with the piston offerings, shit, there stepping it up with DI too. Others may not agree but it is what it is, SIG is on a roll!

The 556Xi, the Gen1 556, and the Gen2 556R All helped pave the way for the 516 and MCX projects and now look, they have developed into the MCX SPEAR. Yeah there were widespread issues with the 556, XI, and R guns but SIG remedied them, then dumped the project in favor of superior platforms. Oh and your wrong because they do still  support the 556 series guns you just have to send them in. Repairs are made through the custom shop. Repairs not able to be made = replacement wherever you go. Product discontinued = New model.

In regards to the M400, it comes in a few different teirs, are you referencing when they first came out with the M400 because If so, times have changed. What did you expect for the first DI AR they brought to market, an LMT. If you were a bit more clear and tried to explain your points to better articulate your situation, it would help and clarify to our fellow members what is wrong with your guns. Others may not know the M400 product line and you just trashed the whole line basically. This is a tech forum not GD, so if you wanna keep whining, do the thread and forum it's due diligence by at least being very clear about your problems.

My M400 SDI 11.5" Pistol sits bedside with me ahead of a few really nice guns because it's so sweet.


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SIG lover yes but not in a monogamous way lol, I love them all like Cheech on "From dusk till Dawn"... We got white pussy, black pussy, Spanish pussy, yellow pussy, hot pussy, good pussy, wet pussy, smelly pussy, heavy pussy, bloody pussy.. etc... You get the picture right! There may be better in the eyes of fanbois right, but there is also good enough!. If I was a betting man, I'd wager that more people have killed other people with inferior products than the Cadillacs you speak of.

How is the PWS “bulky and big”?

It’s the same size footprint as a DI rifle.

Scored a P556xi this week along with a regular P556. They’re pretty reliable but it’s tough to find them at a good price (<$1,500).

I haven't owned a piston pistol, but I have owned a lot of piston AR pattern rifles.  

ACCEPTABLE: POF
GOOD: LWRC
BETTER: HK
BEST: LMT

Lots of people claim "I saw a POF implode at a class ..." but after having owned a half dozen of them (with fairly extensive use) I never had a single issue of any kind.  In fact, they were all more reliable than the "BETTER" option of LWRC.  All of my POF were the basic "Minuteman and Puritan" models.  However, I NEVER ran one hard or in a class.  I really liked the guns but there was a feeling of 'fragility' associated with them.  I couldn't be more subjective if I tried.

I have owned LWRC M6, M6A1, M6A2, M6A3, M6SL, IC, IC SPR, IC Enhanced.  Many units of the IC line.  They must have tight chambers but I had quite a few steel case stick in the chamber, and I do not like the two-thumb screw upper half of the "mono" free float rail design.  However, their ambi lower is great, and the overall guilty of the rifles was good.  After quite a lot of stuck cases I gave up on these a "primary" or "go to" capable guns.  I want to be able to shoot crap Russian steel case reliably.

I don't have any experience with a 5.56 HK piston gun, but all of the MR762A1 I have owned have been phenomenal. I do not, however, like the bare bore or the lack of design innovation (no monolithic upper but a good removable rail / upper interface design, non-ambi lower, captive-tool take down pins) and I'm not crazy about removing the handguard with my front sight attached to maintain the piston system.

LMT is a just a superior product.  Period.  The piston system design, materials employed, G2 BCG design, monolithic upper design, quick change barrel design, ambi lower, etc.  IMNSHO ... LMT is the master race (DI and piston).

I sold everything except LMT and HK.  If I found a reasonably priced HK MR556 variant I would buy it without reservation.  However, they're not worth $3,000 to me.  Frankly, DI is superior unless you're shooting sub-14.5" or suppressed.  You are, so look to LMT.

I have also owned a lot of non-AR piston rifles over the years.  Some examples that quickly come to mind include: FN SCAR, Robinson XCR, Robinson M96, Beretta AR70, Beretta ARX100, Galil 386, Galil ACE, CZ Bren 1, AKs (Bulgarian, Hungarian, Chinese, Russian, Yugoslavian, Egyptian, etc), Steyr AUG, IWI Tavor SAR, FN FS2000, SIG556ER, SIG556 Classic, SIG556 Patrol, Sterling AR-180, Daewoo K2, Springfield Armory SAR-48 (in 5.56 and 7.62) in 16" / 18" / 21" varieties, Ruger Mini 14 / 30 (gag), Leader Dynamics, Masterpeice MPAR556, etc.

I'm an "ALL AR" guy now and have been for quite some time.  However, if you're not set on an AR you might look at a CZ Bren pistol.  I had a couple of them when they first came out and my impression was they were a "product improved" SCAR.  The action on those early guns was BUTTER SMOOTH.  I don't remember the full details, but heard online (ahem ... take that for what its worth) there is some part that has a tendency to fail on this design.  I never experienced this, but I also didn't shoot them much.  "On paper" the CZ Bren 1 was a great design.  Heavy. PIG heavy. Like your HK MR762 with a 2 pound Vortex on it will feel light in comparison heavy, but typical CZ build and material quality which is to say outstanding.

ETA: honestly ... just buy a DI AR pistol.  I am actually down to a handful of DI guns at this point (I have my HK on the EE and will be selling my last LMT piston), because once you buy quality DI you don't need quantity ... or piston.

Haven't tried LMT, but my PWS 5.56 16" upper is heavier than my POF Rogue 308 16.5" upper. This is after I've tried to lightweightify both of them.

Not bulky, but heavy is true.

I only have rounds through the Sig 516 of the brands listed, but I can say they have been fantastic. I have a 16" and a 7.5" 516 upper with a combined ~8,500 rounds through them. And they've been fairly hard miles using them primarily in multi-day classes in a sandy environment.

I am extra impressed with the 7.5 as it has over 2,300 rounds through it and has never had a failure. Again, despite being in a class with some higher rates of fire for a sustained amount of time. The gas block did get hot once or twice through the class but so to my DI rifles under similar drills. Was never a problem.

Don't have nearly as many rounds through my Sig 516 upper, but really like it.  I suspect pretty much all of the NOS is cleared out by now, but when you could pick these up for between $5-600 for the upper, they were a steal.

"Haven't tried LMT, but my PWS 5.56 16" upper is heavier than my POF Rogue 308 16.5" upper. This is after I've tried to lightweightify both of them.

Not bulky, but heavy is true."



-What gen is your PWS upper? I know the older ones were somewhat heavy, but their mod2's are pretty light

Depends on where your parameters for light are. PWS mod 2 16" weight seems to be posted at 6.69 pounds. Can get a lot of AR15 16" setups closer to 6.2 pounds.

Definitely lighter than the 16" LWRC at 7.3 pounds or the MCX Virtus 16" at 7.9.

I have the Mod2, but it's a 16". It's not light at all. My FoxtrotMike G2 and BRN180 uppers are lighter in comparison.

I also build lightweight ARs so I'm partial to what I consider lightweight.

I disagree with you. PWS is competitive with other high end DI AR rifles on the weight.

Didn't read the other replies yet but I hear PWS LSGP is more reliable and less recoil
Than the HK416. Only thing I dislike is their Carbon barrels are all 4140. However they are Nitradited aka Melonite aka Tenifer
So it isn't a deal breaker. Just things I heard no direct experience.

I just got traded for a PWS MK111 Mod2 and it's my new favorite. Holy S this thing shoots great! Recoil impulse is straight therapy man. PWS is my new go to.

I'll  say this.
After doing my research and then ending with a PWS MK111 Mod2, they are my go to now.

PWS built an AR around their gas sytem.
Other companies build the gas system around their ARs.

PWS for the win!

My PWS MK212 absolute fucks.  My DDMK18 was my favorite go-to, until I got my hands on a mint (less that 20 rounds) on the MK212. They don’t make them anymore. Running suppressed is a breeze and it really made my day taking an advanced rifle course. I usually use my MK18 but wanted to see if the PWS (as well as me) handle the pace and round count. Now I have a hard decision to make any time I take a course.

As a side note, I put on. PA 1-6x LPVO with ACSS reticle on it and took it to a long distance class. Due to the barrel length being a bit shorter, I had to figure the dope before the class and during, but once I figured it out…308 out of a 12.75” barrel still does the job.