I have an A1 (ish) build with a brownells retro scope atop the carry handle, and I run this gun suppressed almost exclusively.

Result? Gun is overgassed. Sandman L, for those curious. Solution? Adjustable gas. Nobody seems to make one that would look right and allow me to retain a front sight, so I opted to do it the old school way.

FSB removed from the pencil barrel, I carefully drilled a hole in the side of the FSB, between the gas port and gas tube, sized for a 6-32 screw. All went well until I broke the tap in it. 3 hours of banging later, I finally broke the tap out of it.

Aside from some scratches and the finish needing some repair, the FSB is completely unharmed. However, those threads (or what's left) are completely irreparable. The hole is malformed and will not take new 6-32 threads. Or, at least, I'm not brave enough to risk breaking another tap.

Since this FSB is completely okay, I intend to use it. I have two options, best I can tell.

1. Bore the current hole out to 8-32. This is too large to advance into the gas path and restrict it, but it's suitable to plug the hole and allow me to try again on the other side, again in 6-32. This also would allow me to not risk bottoming the tap out again and breaking it, which is what happened in the first place.    duncecap.png

2. Use a helicoil kit. It seems a helicoil is smaller than 8-32, and would allow me to use the existing hole without much risk. However I don't really know if the helicoil could withstand the pressure that it would be subjected to, and I really don't want to turn a set screw into a projectile.

Thoughts, or suggestions?

I would plug the hole, talk to BRT about your setup and try one of their gas tubes
https://blackrivertactical.com/WP/Adjustable-Gas-System-c6464009

Yeah, this. ^^^^

I had a similar rifle once.
Instead of installing the set screw from the side, I threaded the gas port in the bottom of the FSB (may have had to open it up and don't remember what thread i used).

I then drilled stainless set screws to the diameter gas port I wanted to use or try, installed the set screw, then reinstalled the FSB.

It's not quick to adjust (remove FSB, change restricting screw), but it is seamless and should work nicely for a 100% suppressed rifle.

YMMV

ETA: I picked the set screw size so it couldn't fall into the barrel or the gas tube if it started to walk in either direction.  IIRC, it nestled nicely into the gas tube hole when I threaded it in.

Having a small lathe, I would re-drill/tap to 8/32 and turn the end of the screw to a diameter that fits the inside cavity. Could be done with a drill press and file also.

I wound up drilling the other side, and tapping to 6-32. The original side, I tapped it to 8-32, and cut to length a short section off a 8-32 bolt, threaded the section in, then used a punch to displace some metal so it shouldn't ever come out.

I accidently put the 8-32 screw in a little further than I intended, but that shouldn't be an issue. If anything it may help. It adds a small amount of restriction by default, and more importantly, it means I can't ever screw the 6-32 in so far that it goes all the way in.

Little tip. Set screws are something you don't want to order from Mcmaster carr. Quality is good, but oh man the quantities. I wanted a slightly longer one than what I got, but if I did that, I would have gotten 100 of them. The shorter ones let me get just ten, which was still more than necessary. Oh well. I guess I have nine more set screws if I decide it's necessary to do this nine more times.





I wish I would have read this thread this morning because I would have done this had I considered it.

I have one of these on my LMT 308. It was over gassed from the start. Now it shoots perfectly suppressed. Minimal gas’s blowback. I’m a fan.