Quote Originally Posted by BPTactical View Post
Close but no Banana. On a gas impingment system the gas impulse travels through the gas tube to the boltcarrier. When it hits the boltcarrier interior it causes the boltcarrier to travel rearward, thus unlocking the bolt from the lugs on the barrel extension. If you look at a bolt/carrier combo you can see the mechanism work. The bolt rotates about 20 degrees to lock. This rotation is accomplished by the slot in the boltcarrier and the cam pin that resides in said slot.
A piston AR does the exact same thing only instead of gas pressure to the boltcarrier initiating the rearward boltcarrier movement it is now accomplished by a pushrod/piston arraignment. The gas impulse acts upon the piston/pushrod and is contained at the gasblock then vented. This is why the piston AR will stay cleaner and cooler, you are not directing combustion gases to the boltcarrier.

Which is better? They both have their place I guess. If you are the type that doesn't clean your rifle regularly and doesn't mind the extra weight and mechanical complexity of the piston system then there you go.

I prefer the gas impingment system. Simple to maintain, less mechanical mayhem happening when you pull the trigger and face it, parts eliminated cost nothing and can't malfunction. Not to mention the weight savings.
I do have a piston rifle however, reliability proven and simple:
Avtomat Kalishnakova
So it's just the force of the gas pushing back on the BCG that causes it to unlock, then I can see how both systems works pretty much the same. Why does DI need the gas to actually enter the bolt carrier instead of just acting on the face, like piston?

The other common method for rifles, other than piston or DI, is roller delayed blowback, like the H&K G36, ja?

Thanks for the schooling, and the video is helpful too.

H.