leading around gas block

[porkchopexpress]

hey folks, i just started running 135grain powdercoated bullets through my 300 blk. my gas block loosened up and upon inspection i noticed what looks like leading only after 100 rounds.barrel looks clean.

seems like a bunch of lead for just 100 rounds, is this normal? the result of firing with a loose gas block? thanks

[pretzelxx]

If the lead is on the inside of the barrel that shouldn't cause a gas block to lose up by the bullet slowly moving it.

I would suggest clean and tighten to a higher torque. If that doesn't work, try locktite. But I would always wait for more experience to chime in after me.

[GabbyM]

I'm just a hobbyist not a gunsmith. However in my experience with AR-15's. Your gas block should be fit tighter even before you tighten the set screws. You might want to get a micrometer out and see if the barrel is undersized or your gas block bore is oversize. If the barrel is under you could try a clamp on type block. Short of it is you should have no gas leaking between the block and barrel.

[cmdrted]

as above but when you built it did you try to push the gas block tight againts the barrel stop? most ar platforms need a small gap between the block and that barrel step off. if not poor functioning and possibly some gas blowby because the gas ports don't line up so. this distance is about the thickness of a car-15 handgaurd stop, which is why the gap in the first place.

[porkchopexpress]

appreciate the responses. the screws loosened up was my fault and got blow by.

what amazes and concerns me is the amount of lead from the blow by. i had no idea that much vaporized lead would be present with powder coated cast lead bullets. as of now the cast bulets are on hold and back to jacketed. unless im outside... and the wind at my back.

[bstone5]

A plain base gas check might help in keeping lead out of the barrel.
If a gas check is being used now a bigger diameter cast lead bullet with a gas check should be tried.
The lead should be coming from the gas passing past the bullet as the bullet passes over the bas port in the barrel.

[tomme boy]

Is this a new barrel? Was it shot with jacketed first? You might have a burr on the inside where the port was drilled.

[popper]

ESPC or ASBBT? Look at the bolt - no lead? How fast, what load? Pistol or carbine gas? You will get some minute leading that doesn't show in the barrel, gets pushed into the gas system but not hard to clean. I'm pushing 145gr PB over 1900 in mine, no real leading.

[Jupiter7]

Yep, disassemble the bolt, check for leading on the gas rings and boattail. Carbon fouling should seal off your gas block pretty quick. Check your muzzle device also, if leading, it'll be present there also.

[destrux]

I thought I was getting leading in my gas system and suppressor from my dry tumble fully powder coated bullets, but what looked exactly like lead deposits were actually carbon deposits. Recovered bullets showed no exposed lead. Have you tried scraping the stuff off and melting it with a torch to be sure it's lead?

[xacex]

You sure that is lead? It looks like carbon that was wiped with a cloth. If it is lead you should be able to get it off easy, and it should be pliable. If carbon it will be hard to get off, and will flake. Carbon buildup in that area is common if the gas block is poor fitting.

[porkchopexpress]

ow wow thanks. was worried i could have caused some kind of safety issue. could be carbon, did not come off easy. i will check tonight.

barrel is new. last barrel was drilled too far on the gas port and caused strips of missing lead/powdercoat down the bullet. fired both jacketed and powdercoated through the new barrel.



im using 7.62 130 grain mold sized to .309 and 18 grns lil gun. candy purple coating. my gun doesnt seem to like the black powdercoat.

[xacex]

im using 7.62 130 grain mold sized to .309 and 18 grns lil gun. candy purple coating. my gun doesnt seem to like the black powdercoat.

Gas checked? I would also shoot 100 or so jacketed bullets down the bore just to smooth the lands and grooves out from rifling, and make sure there is no bur in the gas port left with a new barrel. I have had some AR barrels that would just not break in with cast. To soft on the bore. Consider another powder as well. Lil gun has a reputation of eroding throats, and forcing cones. It has a long and slow burn profile. You will notice that it will heat up a barrel faster than your other options.