[MatthewVanitas]

Greetings,
I was reflecting on my upcoming AR purchase, and lamenting that .223 HKs are in short supply, as well as being less familiar to me, and having far fewer modular options.

Then the thought occurred to me: how hard would it be for a qualified designer to make a roller-delayed blowback AR-15? Obviously, not a home-tinker job, and there's probably not really any market for it, but is there anything that makes it totally undoable?

I mainly ask for two reasons:

1) It seems to be a widely-held opinion that the AR series is one of the most erongomic rifles out there.
2) Roller-delayed blowback has a cult-following on this board that insists that RDB is far superior to Direct Gas Impingement and Short/Long Piston.

I don't expect that it's going to happen, but just curious as to whether it'd be, in abstract, a good idea. Has any designer ever even played with this idea in the past?

Thanks for any info, -MV

[Onmilo]

Anything is possible.
As for practical or feasible the answer is no.
There is no real reason to make a major redesign of this action type though the Taiwanese Military did a pretty good job of turning the M16 into an impinging piston locked breech design and Heckler and Koch modified the design even further ultimately ending up with the G36/XM8 design.

[Correia]

You can make an upper that fits on an AR lower that does pretty much anything. How much money you got? :)

[boing]

In summary, "anything is possible" with "enough money". :)

[HPJeep]

Interesting theory. A RDB upper on a AR platform. I guess I would not see why this is much better than direct impingement. Would be a little more reliable but both types are quite dirty in the action. A piston would be the way to go as far as keeping the action cleaner, more reliable, not as hot, and cheaper than a RDB upper on the AR. Yet this out of the box thinking is how new or improved designs come around. Keep playing with these different ideas! My idea is to take my AK47 and make it a tack driver like an AR. I think it can't be done due to the inherent inaccuracy of the AK's action and maybe even the bullet design too.

[jobu07]

even the bullet design too.
You won't say that if you shoot an AR chamered in 7.62x39...

[Father Knows Best]

Interesting theory. A RDB upper on a AR platform. I guess I would not see why this is much better than direct impingement. Would be a little more reliable but both types are quite dirty in the action. A piston would be the way to go as far as keeping the action cleaner, more reliable, not as hot, and cheaper than a RDB upper on the AR.

What makes you say that the RDB is "quite dirty in the action"? In my experience, the AR is far and away the dirtiest, because it ports combustion gases directly into the action. The RDB does not.

[444]

As has been mentioned, this whole gas system thing is a problem invented on the internet, in real life, it isn't an issue. But certainly anything could be built if there was money in it for the builder.
But, then it wouldn't be an AR15.