Staking AR gas key

A

antsi

New member
Last week I completed my first AR build. I purchased the upper as a complete unit in a face to face sale. The seller described the upper as an LAR upper receiver with a DPMS bolt carrier group and a Wilson chrome lined barrel.

I built up a stripped lower and put a stock on it and was initially very pleased with the results - then I started getting some malfunctions. It was an odd malfunction - the shot would fire normally and the empty case would eject, and the gun would seem to go back in battery, only it would not pick up a new cartridge to feed. So, despite there being plenty of ammo in the mag, and the mag being seated, the bolt would be forward with nothing in the chamber.

When I took the gun apart to clean it, I noticed that the gas key (hope that's the right term - the little gas tube thing on the top of the bolt carrier) had come loose. The allen screws were loose. The parts were all still held together, but they were flopping around loosely.

There are grooves indented across the top of the screws and across the top of the bolt carrier group as if someone had tried to stake them in place - but obviously it wasn't done properly because it came loose.

For the meantime I re-tightened the allen screws and used loctite. I know this is not a long term solution.

I don't have any punches or cold chisels that the right size for this job, so I'll have to buy a tool for this job.

I would appreciate any hints or tips about -
the best tool to do this job
how to do the job
how to know it's done right
any pitfalls or problems to avoid

One other thing - do the allen screws have to be torqued to a specific setting, or is just "tight" okay?

Thanks!
 
B

Bartholomew Roberts

Moderator
MOACKS is a very slick tool that is purpose built to give a proper staking job; but a Starrett punch and a hammer will work too.

Proper torque is a minimum of 40 inch-pounds with a do not exceed torque of 80 inch-pounds. I think 60 is the typical value used.
 
F

freakshow10mm

Moderator
A lot of people make a big deal about of staking. Hammer and punch is all you need. It doesn't need to look like a gorilla crunched it. Just enough so the screws don't turn is plenty.
 
T

Technosavant

New member
Retighten, use hammer/punch combo (I tend to prefer a center punch rather than a more normal set punch). You want to displace the metal from the sides of the gas key so it's touching the screws themselves. Don't crack the metal, just bend it. Sometimes you have to wail pretty good to get it going.

Staking a BCG properly isn't rocket science, but for some reason most of the "commercial" type ARs just aren't done properly. Easy enough to fix, but you wonder why the maker didn't just do it right to begin with.
 
4

44 AMP

Staff
US Army protocol circa 1975

Bolt carrier key screws torqued to 40 in/lbs, then staked.
Staking was done with a center punch and hammer.

Worked for the M16A1 then, ought to work for an AR now.
 
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