Anyone running a piston gas setup on their Grendel?

[BjornF16]

I've just finished my initial setup of my SBR Grendel (as well as been playing more with my 300 BLK)...

Don't really like all the gas in my face. Is anyone running an Adams Arms setup on their Grendel and/or 300 BLK?

I'd be interested in hearing how well they function, reliability especially.

[cory]

Following. I've, also, toyed with this idea.

[Steamburn]

Adam arms on a 5.56 and Syrac on 6.5 Grendel.
Both work perfectly.
Syrac has a wider range of adjustments, less expensive and a more advance design than the Adams Arms. Both were designed by the same individual. The Adams Arms is an earlier design.
I think the Syrac has more thought put into it.

[Jackem]

Tagging in to the thread. I have an LWRC and like the piston operated 5.56 so much I'd like my 6.5 set up the same way.

[montana]

I have an Adam Arms piston on a suppressed short 5,56 barrel. There is less gas blow back to my face and it runs flawlessly. I can also run my suppressor on my 16" DI barrels and have had zero problems with those. I'm not sensitive to the blow back as most apparently as I have never had a problem with it. All things being the same if I could live with the DI system I would stick with it. I converted back 3 other AR rifles to the DI from the gas piston system. The DI recoil system is milder, more accurate and lighter in weight than a gas piston set up. My Adam Arms gas pistons ran great and are self regulating but the increase in recoil and weight were significant . I have read where some people had small gas ports which can make the gas piston set up short stroke. If you have an over sized gas port the Adam Arms piston will run great but an adjustable gas block on a DI system will also run with out problems. I have done a 180 with my thoughts on gas pistons and try to avoid them since the DI system is superior in the AR platform in my opinion.

[Post Toastie]

I currently have the AA setup on a 16" 6.8SPC upper and it works great. Interested in hearing about the Syrac on a 6.5.

[LRRPF52]

Battlefield Las Vegas/Henderson Defense has some interesting things to say about parts failure on different designs.

With their guns and the high volume full auto they shoot, it isn't a matter of "if" but "when", so they have had to really track failures and organize their logistics system around parts replacements on a wide variety of full auto firearms. The owner spends a lot of his time ordering replacement parts.

They get about 20,000 rounds out of AR15 barrels and bolts, with bolt failures occasionally sooner.

The owner mentioned that of all the op-rod driven systems they have seen come through their business, the only op-rod design that has not broken was the HK MR556, but the barrels started key-holing after 10,000rds. He would not say which companies op-rod designs broke early on them, and admitted he didn't try them all, but that several popular ones he wished not to mention fail very early in their shoot schedule.

They shoot tens of thousands of rounds through any single gun per week, with a lot of out-of-state customers and foreigners who have seen all the movies, played all the video games, and have very specific ideas about what they want because they saw some SEALs with it on a movie, or saw it on some player list on Call of Duty.

Time is money for that business, and some designs require parts replacement so often, that they start to lose their margins because the staff (dozens of veterans with combat experience and weapons repair/maintenance training) get bogged down replacing broken carriers, bent op-rods, blown out gas blocks, broken cam pins, broken bolts, etc. The only op-rod design that works well for them is the HK, and they actually use a US-made clone of it with better barrels that don't crap out so early like the HK pipes do.

In my personal dealings with different units that have the option to use HK416's, the results have been mixed to unfavorable. The Danes pull the trigger mechanism out and use them in standard M4's, while other units just leave the guns in the arms room and use SOPMOD Block II M4A1's with the new RIS, 10.3" barrels, newer suppressors, etc.

I have also worked with different people who have done a lot of RDT&E on their own op-rod designs, and most go back to the standard Stoner internal expansion system.

For dealing with gas blow-back, the right charge handle and gas system set-up can alleviate a lot of that, but even on op-rod guns, you still see it. I was running a class recently where an adjustable gas op-rod SBR was being used, and it ran well, but would not lock back on the empty mags with the gas setting it was on for pleasant handling.

Another thing that sticks out to me watching all this unfold is that some of the prominent figures who were instrumental in development of some of these designs, don't use them in their regular training courses. I was carefully watching with interest as the op-rod trend came into favor, and that fact alone told me all I needed to know, aside from my own positive experiences with reliability using the standard internal expansion system.

Most of my 5.56 SBR work has been with 11.5" guns, and I don't recall any malfs with them dating back a long time now.

[Klem]

The gas piston idea in the AR has been more a fashion than a revolution, and so has the 300BLK calibre.

Both the AR gas piston and 300BLK have been around for long enough to be properly trialled. Yet in both cases they remain more a niche idea still advertised by their manufacturers. Any innovation that represents a real benefit over the existing solution will gather momentum by itself once introduced (e.g. refrigeration). This has not happened with pistons or the 300BLK.

More specifically, a gas piston on a 300BLK does not work. On the 300BLK forum the sum total of the threads on this subject is that not a single op reported that they work. The reason being pistons need more gas pressure to work and the 300BLK is under-gassed as a calibre to start with. The 30cal barrel volume is too large for the amount of gas generated in a small case. For this reason barrel manufacturers have brought back their gas bocks to pistol-length gas systems with a few exceptions still using carbine-length on their 16" only (when dwell time becomes more of an issue than lack of gas).

You will still experience spit in the face using a piston. This is because suppressor spit mostly comes from the chamber, not the gas system.

Bottom line, there are as many disadvantages of using a piston as advantages. Pistons are not cheap so you end up paying more for a gun that can work just as well with DI. That's why they haven't taken off. Now that adjustable gas has entered the market there is even less reason to go piston.

In a Grendel... Imagine your current system having to work a little harder. If there is gas to spare then a piston will work. While your gun will be heavier, your wallet will be lighter.

[Rainman]

I have piston ARs from LWRC, Ruger and Sig as well as DI ARs from Sig and my custom 18" BHW .264 LBC. Two or three years ago I was biased toward piston but am neutral now and about to order a new light weight 6.5 Grendel DI upper from Alexander Arms. Light weight and balance go to DI guns. To me, while the recoil impulses are different, I can't honestly say the recoil from one is heavier than the other (exception with with my Sig .308 of course). I will only own a .308 in piston due to the volume of powder and the fact I have several pounds of older W 748 that is very dirty. Accuracy wise there may be a slight advantage to DI still but I think that goes more to individual guns and shooters these days with the more sophisticated piston systems now available. A downside with piston guns is that all the systems are proprietary so you can get stuck without a soulution in the field if you have a problem. I regularly shoot half MOA with my LBC/Grendel with several handloads and Hornady 123 factory ammo. A Squad Leader at the loacal Navy Base shoots my gun with the same loads consistently into .30" five shot groups at a pace I call rapid fire. The only excuse I have is that his first MOS was as an armorer and then he was a full time marksmanship instructor for several years. I can live with that and continue to improve by listening to him, a real nice guy willing to teach an old dog new tricks.

[tpk]

I'm have a 12.5" Grendel upper with an Adams carbine length system. It works great but I didn't really notice a reduction in gas in the face.

[LRRPF52]

Another thing I notice with the op-rod driven guns is that they have noticeable torque that isn't present on Stoner gas guns.

Since I just don't have reliability issues with the Stoner design, and could count the number of malfs I had on M16's and M4's on one hand spanning a decade, I won't break what doesn't need fixing for me.

I will also second what Klem said about 300 BLK and op rods. They don't work, for the exact reasons he stated.

[Capt. Morgan]

I have a Precision Firearms build with the Adams Arms gas piston. I'm a low-volume shooter, so I can't speak to reliability. But at 100 yards it can do overlapping bullet holes when I do my part of the deal. Cleaning sessions are a breeze too, important to me since cleaning is my least favorite task.

Really, nothing not to like for me.

[kb18no1]

Just get a gas buster charging handle.

http://www.bravocompanyusa.com/PRI-Gas-Buster-Charging-Handle-p/pri%20m84%20gb%2005-0032.htm

[jkingrph]

I have two, a mid length, and a full length rifle, both with Adams Arms units. Both are probably about six or seven years old, home assembled. Both function perfectly and the guns accuracy compares favorably with my direct impingement system guns. That said, I am a low volume shooter so cannot really comment about long term reliability, in terms of number of rounds cycled. I have on the other hand run quite a few rounds through the big gun fire forming some of the IMI 7.62x39 brass I bought when Grendel brass was scarce and expensive. The gun functioned perfectly, cycling and loading the fire forming rounds. I have not noticed "gas in the face" and the receivers and trigger groups remain clean.

[Klem]

Do you shoot the AA uppers with a suppressor?