12.5" mid-length gas port size

[Mhan7]

I realize my last statement sounds a little convoluted. So what I'm trying to say... Maybe they just tooled it that way, to get the proper pressure drop, based on physical testing, but without creating weird new drill sizes. A #49 drill measures .073", and .083" corresponds to 2.1mm. That might have been a very specific geometry, based on a very specific set of testing parameters.

Who knows. But it's fun to think about.

[montana]

I realize my last statement sounds a little convoluted. So what I'm trying to say... Maybe they just tooled it that way, to get the proper pressure drop, based on physical testing, but without creating weird new drill sizes. A #49 drill measures .073", and .083" corresponds to 2.1mm. That might have been a very specific geometry, based on a very specific set of testing parameters.

Who knows. But it's fun to think about.

A gas port with 2 different size steps, creating a different gas flow dynamic. Maybe, but it is a new one to me.

[Mhan7]

A gas port with 2 different size steps, creating a different gas flow dynamic. Maybe, but it is a new one to me.

Not necessarily a *different* dynamic, just a *desired* dynamic. Based on the dates that you gave for manufacture (you mentioned the 90s), it would have been before adjustable gas blocks and adjustable mass were well known, if even a thing at all. Regardless of whether my guess is even in the ballpark, I'd bet dimes to dollars that it's a thermodynamic consideration of some sort, primarily.

But like I said... I could be (and probably am) wrong. Just taking a stab at it.