Several years ago, when Walmart was closing out their AR's, I bought a Bushmaster flattop. Have had it stuck back in the safe, figuring I'd get around to doing something with sometime. My other AR's are either scoped, or have a reflex sight. I thought I'd set the Bushmaster up with open sights, just to play around with. I had a Midwest Industries rear, and a YHM A-2 gas block front sight, in my box of AR parts, and figured I'd use those because I already had them. The gas block on the Bushmaster had no way to attach a front sight, so it had to be come off and be replaced. Gas tube pin came out fine, as did one of the pins holding the gas block, but the other would not budge. It was stuck big time, and I could not remove it. I ended up cutting the block with a Dremel tool until enough of the pin was removed, and then it came out. I go to put the new sight on, and it either will not line up with the holes in the barrel, or else the holes in the sight are not right, because neither pin will go back in. I'm starting to think that it might be a problem with the barrel, and not with the gas block. I'm now thinking about just putting on a clamp-on style block with a rail, and buying a front sight that attaches to it. Anyone ever had such a thing happen?

clamp on or one with set screws.

IIRC the taper holes are drilled with the base on the barrel and no two may be quite the same. All I know for sure is I never wanted a pinned sight anyway as you can't zero the rear sight for windage and then adjust the front to center if the front is pinned wrong.

i bought a bushmaster with a similar problem, change out the barrel or I just got rid of the gun, too much junk on it.

BTW drive the otehr taper pin back in with 640 loctite and cut off ends, dremel smooth and your barrel is good to clamp or set screw. Easy peasy. Takes a few minutes max.

and even I can do it blindfolded. LOL. ITs NOT hard to fix.

I just went ahead and put a clamp on gas block on. Figured that would be the easy fix. I really wanted to use that YHM front sight, as it's a lot sturdier than any clamp on front sight will be. But, it is what it is, and I'll learn to like it.