Gas impingement vs. gas piston

[Trooper]

http://www.gundigest.com/tactical-gear/tactical-guns/ar-15-gas-impingement-vs-piston?et_mid=679047&rid=235843475

[LRRPF52]

Good article. I would add that the filth from carbon fouling is placed in a different location on an op-rid driven gun, versus DI.

Colt made a prototype/test op-rod AR15 back in 1968 called the Model 703. It was deemed inferior to the standard AR15 across the board.

[NugginFutz]

Interesting - looks like the op-rod is linked to the BCG, and the buffer spring is the only return spring in the system. While not an obvious point of failure, I imagine that linkage took quite a beating. Any info on why the design was ultimately abandoned?

[LRRPF52]

Interesting - looks like the op-rod is linked to the BCG, and the buffer spring is the only return spring in the system. While not an obvious point of failure, I imagine that linkage took quite a beating. Any info on why the design was ultimately abandoned?

Heavier, put the point of balance way forward, no reliability improvements, less accurate, poorer handling characteristics, harder to field strip, more expensive to manufacture, more moving parts. Recoil impulse and muzzle climb were worse that the in-line AR15/Stoner DI system.

Op rod designs are a step backwards from DI in my opinion and in the progression of operating system development over the last century. They make a lot of sense in certain rifles, and especially belt-fed machineguns, but not in the AR15.

[Klem]

Interesting article, but my experience with a piston (Adams Arms) has a few differences.

The action is cleaner at the end of a session...providing you don't use a suppressor. With suppressors crud comes back around the case on extraction and you end up having to clean the action anyway. OK, you don't have to scrape that evil black stuff that sticks to the back of the bolt but apart from that, suppressed piston uppers get just as filthy.

I have not noticed any less accuracy with the piston in two guns I have seen it used. The pistons were certainly not more accurate, but no less accurate than impingement.

The reviewer didn't mention handguards. If you want to push the handguard forward of the gas block your choice of handguards are suddenly limited. The trend of longer handguards over gas blocks doesn't work so well with pistons.

They are bulkier and heavier at exactly the spot you don't want it, forward.

It detracts from the idea of "free-floating" to have more bulk rigidly clamped to the barrel than an impingement system.

The reviewer tip-toe's round the cost aspect. There's no fence-sitting on cost. If you choose quality parts for your rigs then pistons will cost more.

One side-note...Pistons take more gas to cycle than impingement, which is no big deal UNLESS you have a 300Blackout. From experience and reading the forum no-one uses them in Blackout's because they don't reliably cycle. That calibre is on the raggedy edge of being under-gassed even with impingement.

[NugginFutz]

Heavier, out the point of balance way forward, no reliability improvements, less accurate, poorer handling characteristics, harder to field strip, more expensive to manufacture, more moving parts. Recoil impulse and muzzle climb were worse that the in-line AR15/Stoner DI system.

Ok, but other than that, what was the issue?