[Charles Martel]

Given that the AR is a direct impingement platform, and assuming that at least some of these options have a larger powder capacity, does that possibly impact the functioning of that system, perhaps causing more fouling, more frequent cleaning, etc?

Armalite used the DI gas system design on the AR-10 first, with few changes made when scaling it down to the 5.56. Remember that only a small portion of the combustion gases are diverted to operate the action; only so much is going to flow through that drilled gas port - barrel length probably has a bigger impact on it than case capacity.

Naturally, gunpowder formulation *is* something that designers must be careful with when dealing with the DI design.

[Hardastarboard]

When you say it that way - duh. Of course - now I get it. It's not how much powder gets burned, but how much gas overall gets diverted. That would be dependent upon the port size, and I assume the overall size of the gas tube.

Thanks for answering my question.