Like another poster, I too am new to the AR world, although I've wanted one for years and have had the oportunity to fire several. Recently, I was finally able to satisfy my urge when I friend of mine sold me a never fired  Bushy DCM for a very reasonable price.

My question is this: What is the advantage (if any) to a gas operated semi vs a blowback? From an engineering standpoint, I would think a gas operated, having more parts to fail, would be less reliable than a blowback, yet the AR, which I consider to be an excellent rifle, is gas operated.

Anyway, thanks for any info. I thought about looking it up online, but you guys are better than books.

regards,

-legrue

A blowback design becomes impractical past a certain level.  Either the bolt becomes too heavy or the recoil spring is so stiff you can't manually operate the action.  

The advantage of gas actions is that you can use as much or as little gas as you need for your purposes.  This is taken to a higher level in the FAL and the M-96, where you can fine tune the amount of gas coming back into the action.

One of the AR's commonly cited design flaws is that the gas comes directly back into the bolt carrier area, dumping the fouling into the action.  The AR, FAL, etc., use a more indirect system where the gas impinges on a piston some distance away from the bolt.

The blow back design is suitable only for certain types of guns. I think the max for handguns is the 9mm, there is only 9mm pistol that had a blow back design and it was the Detonics Pocket Pistol. I understand the recoil was pretty substantial. The 9mm & 45ACP sub machine gun UZIs & MACs had a blow back design also, which probably the limit. The 556Nato round is probably much too powerful for blowback.

Like everything else, a lot depends on the design, the materials, and manufacture techniques used which determines its longevity.

Tastes great!  Less filling!!

Just like either or, there's a case to be made for both. My G3 is called a "blowback" design although one could make the case it is indeed a gas op. Like the other post says, the bolt is fairly stout & heavy to take the pressure.

A have an AR-15 & just bought an AR-10. I sold my L1A1 as I got sick & !@#$%^&* tired of having to adjust the gas regulator when changing lots/brands of ammo. There are some complicated gas designs out there but I can't recall exactly which ones right now.  >gg<

i like my rifle like my colon

gas operated.

Gas operated depends alot on the design, as Ken Mays posted, the AR gas system sends hot gas and soot right back into the bolt area (though another post here claims this doesn't effect reliability after 7K rounds), whereas other designs, such as the AK and M1A, have the gas hit a piston, which isolates the combustion soot from the bolt to a certain extent.

I think once a cartridge gets beyond a certain amount of power, recoil operated is not a design option anymore and gas operation is the only feasible design option.