Hello,

After changing some parts around on a Service Rifle upper (taking the barrel and float tube off an A2 upper, and installing them on a A4 upper), I noticed a pretty fair gas leak around the FSB that wasn't there before we took everything apart.  The A4 thing isn't quite working out the way I'd hoped, so the barrel and float tube are back on the A2 upper while I wait on a new WOA 20" Service Rifle tube.  I cleaned up around the FSB pretty well while things were apart; haven't had a chance to fire it since, so I don't know if it's gonna leak again.

What would make this leak like it did?  Just the FSB not lined up over the gas port, or what?  The gun functioned fine, so I wasn't too worried, but I'd rather not have the gun leaking where it ain't supposed to!

TIA,

nuk

Did you line up the port of the tube with the top of the barrel ??

Are you having cycling problems ??

Do hear some leakage when you fire a round ?

Any chance of some close up pics ?

Well, like I said, the gun functioned fine for... I don't know... somewhere around 500rds thru it since the initial swap.  No hiccups.  None.  This is in NRA High Power type shooting... single-load slow fire @ 200 & 600, 'rapid' fire @ 200/300.  Not sure how the heck I would hear any leakage w/ hearing protection on and the blast of the shot...  and like I said, I cleaned everything up when doing the swap back and haven't fired it since.  Should get to the range tomorrow and work on re-sighting everything in since the FSB moved.

The best way I can describe it is most of it was coming out from under the rear of the FSB on the port side, maybe at a 10 o'clock angle... assuming that straight down range would be 12 o'clock.  There was a fair amount of powder residue between the shoulder of the barrel & the FSB.  The FSB never got moved, IIRC, cuz we had some other weird stuff going on.  The gas tube got un pinned and removed, but I don't believe we moved the FSB.

Thanks,

nuk

Seems I remember that the manual for TM on the 16 states this is normal for some time after installing a FSB, but should stop after a few rounds.  My pencil barrel rifle leaks some but I think it has almost quit after a few hundred rounds.  May take a while for the powder residue to stop the leaking.  If the functioning is ok why worry?