I was taking the free float tube off my 16" gun to have some cooling slots cut in it. As long as it was off, I thought I might as well go ahead and swap out the stainless barrel on it for the new chrome-lined Bushy pencil barrel I purchased a few months ago.

Problem 1: The front sight tower on the "new" Bushy barrel was so corroded to the barrel that I damned near never got it off.

Problem 2: The gas port on the Bushy barrel looks screwed up to me. Not only is it a lot smaller than the one on the old barrel but, it's also off-center. What do you guys who know something about this stuff think?

The old barrel is on top; the new Bushmaster on the bottom. Sorry my photography skills suck even worse than my gunsmithing.

Thanks in advance for your responses.  SD

Wait. there's also the matter of the grooves for the FSB pins being dimensionally way out of whack.

bump

You critters shouldn't be messing with that Armor level maintenance!  I wish there was a Bureau I could report you to!

Quoted: Nice, are those 1X7s? BFI once told me, on this forum IIRC, that they Parkerize their "military" barrels to "spec" and that only their civilian barrels were shiny under the FSB. Just checking for the files. Did you mic the gas ports or are you using a calibrated eyeball? The chamfer on the gas port of the original barrel may be throwing off your estimate. An extra deep chamfer is often used to "correct" any misalignment between the gas ports in the barrel and FSB. Yep, it looks like either the gas port is mislocated or the FSB isn't aligned properly.

They're both 1/9's. I've had pretty good luck with 1/9's with heavy bullets; as long as they're Sierra's.

I tried to put a 1/16" bit down the gas port and it wouldn't even come close to going in.

I talked to Jim @ BM and he said to just drill it out to 1/16" and if it didn't work, they'd replace the barrel. Can't beat that.

SD

Quoted: An extra deep chamfer is often used to "correct" any misalignment between the gas ports in the barrel and FSB.

This will also fix some gas system short cyclign problems.  Many times you don't have to completely drill a gas port to improve gas flow, a deep chamfer, acting sort of like an expansion chamber, will help gas system operation as well.