Harrison Beene (harrisonbeen) said:

This leads me to the next question, Is a piston system really cleaner enough, reliable and durable enough to make it worthwhile on a military rifle?  

Now that sound suppressors are becoming more common, there is more of an emphasis of keeping propellant gasses away from the shooter's face.  All of the NGSW finalists used pistons, as does FN's LICC .264 rifle.   SIG and FN both produce DI rifles, so it is notable that they developed piston rifles for their military proposals.

From reading posts on forums and watching some of the vets on youtube that do reviews it seems most prefer to use versions of DI AR15s, M4 or MK18.

I don't do enough high volume testing to compare one system to another and come up with a reasonable conclusion. I need to find more real test results where the military has done extensive testing.   I know the SCAR16  and 416 test results proved they are among the best.  The 416 is not a folding stock design, several on the market are. Should we believe the results of the filthy 14 or is it advertising hype?

I've had several AR180s over the years. In 2010 I wanted to modernize one so I designed an aluminum monolithic upper. I had 300ft of extrusion made with 1913 rails  full length. I machined slightly modified carriers then used the rest of the parts from the AR180 I had. It was a operating, piston driven, folding stock prototype that didn't seem any different from the AR180 except for the monolithic rail. I posted some info on a few forums I visited back then and there was zero interest.  Shortly thereafter I fired my shop foreman and run my embezzling wife off and that was the end of that. 10 years later Brownells come up with the BRN180 and SIG comes up with something similar so of course I want to try it.

It is a hobby, none of this stuff is going to make a difference in my shooting needs I just need to learn to stop punching the "place order" button.

Sorry for the derail, back to your discussion.

Harrison Beene (harrisonbeen) said:

I've had several AR180s over the years. In 2010 I wanted to modernize one so I designed an aluminum monolithic upper. I had 300ft of extrusion made with 1913 rails  full length. I machined slightly modified carriers then used the rest of the parts from the AR180 I had. It was a operating, piston driven, folding stock prototype that didn't seem any different from the AR180 except for the monolithic rail. I posted some info on a few forums I visited back then and there was zero interest.  Shortly thereafter I fired my shop foreman and run my embezzling wife off and that was the end of that. 10 years later Brownells come up with the BRN180 and SIG comes up with something similar so of course I want to try it.

With that background, I think you owe it to yourself to have some example of a modern AR180. Either the BRN-180 or the new SIG LT, but something to scratch that itch.

Here's more info on the LT:

https://www.ar15.com/forums/Armory/MCX-Generation-3-SPEAR-LT/45-534561/

Previous MCX gen

https://www.ar15.com/forums/Armory/Sig-MCX-Virtus/45-479609/

BRN-180 info

https://www.ar15.com/forums/AR-15/BRN-180-Review/126-740125/

Gotta say the LT is handsome:

But BRN-180 is also very striking:

Waiting for gen 2 Perun which will considerably reduce the height of the receiver , it is supposedly already in the works

The double-decker design not my flavor , but its otherwise a very nice gun. The gen 1 design was kinda driven by keeping compatibilty with ar15 parts to the maximum. 

Harrison Beene (harrisonbeen) said:

I don't do enough high volume testing to compare one system to another and come up with a reasonable conclusion. I need to find more real test results where the military has done extensive testing.   I know the SCAR16  and 416 test results proved they are among the best.  The 416 is not a folding stock design, several on the market are. Should we believe the results of the filthy 14 or is it advertising hype?

I do not have a very extensive experience with the DI AR-15, but my understanding is that due to the very long bolt carrier, this design is reliable as long as the lubrication is correct.

The US started to lubricate the M16 with the same light oil (VV-L-800) and grease (130-A) as the M14, which used the same lubricant as the M1 Garand. Both those lubricants were low temperature (max ~80°C for the 130-A and ~115°C for the VV-L-800).

Then, around 1968, the VV-L-800 was replaced by the O-158 LSA, which was much better suited for the full-auto M16 than the rifle lubes used for the Garand and M14.

The LSA was then replaced with the S-758 CLP, which seems to be slightly less resistant to high temperature than the LSA (but could be used even in extreme cold), and now there is a move towards another CLP without Teflon.

So, as long as you use a high temperature lubricant and do not overheat your rifle, a DI rifle should be as reliable as a piston-driven rifle.

Now, if you plan to use a suppressor, a piston rifle will run cleaner (as a general rule of thumb), but the exact suppressor design plays a large role in the equation, some suppressors could foul any rifle (DI or piston) in less than 30 rounds, others allow rifles to fire 1200 rounds without cleaning (and without stoppages).

The interest of a piston AR is that the lube film is less prone to cook when the rifle is fired a lot, and when using S-758 lubricant.

SCAR-L and HK416 are proven rifle design, but the Colt Canada C7 & C8 (DI) are also very well regarded.

The main difference between a C7/C8 and a HK416 (except the piston), is that if you chamber a .300 AAC round in a C7/C8 and press the trigger, the gun will explode, while if you do the same thing in a 416 the gun will fire without exploding.

Same thing with firing the gun with bore obstruction, most DI rifles will just explode when a SCAR-L and a 416 will survive. That's a very small advantage for a civilian rifle, but something to take into account for a military rifle.

EmericD said:

The main difference between a C7/C8 and a HK416 (except the piston), is that if you chamber a .300 AAC round in a C7/C8 and press the trigger, the gun will explode, while if you do the same thing in a 416 the gun will fire without exploding. Same thing with firing the gun with bore obstruction, most DI rifles will just explode when a SCAR-L and a 416 will survive.

Very interesting. Is this a function of being Piston, or just a function of these being more modern, stronger rifles?

I know the SCAR 16 in particular is regarded as extremely tough.

Here in Vegas, there is a FA rental range thats super popular with tourists, and as a result may be one of the highest FA users around outside of perhaps the frontlines of a war. Millions of rounds a year FA for over a decade now.

https://www.ar15.com/forums/ar-15/High-round-count-AR-M4-s-over-100-000-rounds-and-how-they-have-handled-on-our-range/118-677135/

(the above thread is a wealth of information I suggest everyone peruse)

YouTube

Battlefield Vegas Visit & Extreme Round Count Failure Points (AR-15, AK-47s, 1911s, Glocks....) (HD)

Met up with Sean, armorer for Battlefield Vegas, to discuss common failure points that some of our most popular firearms see.Sign up for my email list here:w...

At 8:10 discussion of the SCAR16 begins. There is a 16 there that has had 200k rounds fired FA with only replacing 2 parts, the barrel and the hammer. (In fairness they only replace a barrel if it starts to keyhole at 10m). But of all the myriad guns they rent and shoot the SCAR16 was the toughest of all. 

gatnerd said:

Very interesting. Is this a function of being Piston, or just a function of these being more modern, stronger rifles?

I really don't know. The C7/C8 are as modern as a 416, so maybe it's just because "not blowing" was a requirement passed to HK, and not Colt Canada?

During our FPSA program, the French Company Verney-Carron Defense proposed an AR-10 derivative. The first obstruction tests produced frame fragmentation, like the original AR-10. When we said to them that we were in 2019 and this wasn't allowed anymore, they changed the design and the second series of rifles could sustain bore obstructions without blowing and throwing fragments...

gatnerd said:

There is a 16 there that has had 200k rounds fired FA with only replacing 2 parts, the barrel and the hammer.

When the GIGN deployed in Afghanistan to train the Afghan police, they bring some of their G36 with them. The guns stays there for 10 years, used to train thousands of police officers.

One rifle shot 144,000 rounds and another shot 140,000 rounds, without anything more than day-to-day cleaning, and barrels were still OK. Those rifles were shot only in semi-auto, and were never pushed anywhere close to their limits. With this kind of fire regime, barrels from FN Herstal and HK could last forever.

Modern rifles can sustain a lot of abuse, that's probably why the USMC thought that a M27 could replace a M249.

Getting back to Germany, nice piece by DW on the issues Germany is having implementing its $100 Billion re-armament.

YouTube

100 billion euros for Germany's armed forces: Why hardly anything has arrived so far | DW News

The government has earmarked 100 billion euros to bring the Bundeswehr up to speed for its modern-day purposes, a sum, that experts claim isn't hardly enough...

SIG LT bolt  since I haven't seen any photos up close, looks close to my Titan bolt.