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AR gas key screw thread

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Titanium
Joined
Aug 22, 2011
Location
Oregon coast
My brand new AR-15, I field stripped it to clean and lubricate it before test firing tonight, anticipating shooting it tomorrow.

What? The gas key has only one screw holding it on. Both screw hole edges are staked but it looks like there never was a screw in the rear hole.

I know that American made socket screws are supposed to be grade 8, so if I can find one that fits in this little town I think I can torque it correctly and come up with a new staking process, but all I could screen off the web was that they are 8-32 X 1/4", is that correct? If so the next search will be for an American made 8-32 X 1/4" screw.

There is a lot of talk in forums about "common" screws not being grade 8 but I don't believe that is a problem with US made screws, except for counterfeits.
Thanks in advance,
parts
 
He's talking about the gas key on the carrier, not the gas block on the barrel. No bore to distort there. When torquing the screw, you'll feel it stretch so do take it easy.
 
Thanks so much for the replies, I've been a 1911 guy and collector of early semi-automatic pistols all my life, but have owned only a few rifles.

Until recently I hated the AR system because of the aluminum in the design, but though it's still ugly I watched a youtube video of a guy shooting one on full auto to destruction, it was horrible abuse! In spite of smoking and getting red hot(the guy wore welding gloves), he went through a small mountain of magazines before it finally blew a round out the side of the barrel!

So I've changed my mind about the AR and Eugene Stoner.

Old dogs,and new tricks,,ya know.
 
Iirc correctly, torque the screw to 35 inch pounds and stake in place with a punch

There are a lot of different opinions offered as facts about that. One maker says 56 inch pounds, 35-40 is a common call out, one says 58-60, and staking, oh my! The flames I've read as people disagree on it. Gonna add that to religion and politics.
I torqued to 58, gotta pick one. The staking can be done with a punch and hammer but I made a tool after Brownell's pattern today, it drives a cone setscrew against both sides of the key near the top which pushes metal over the top edge of the screw head.
Yeah, it would have been easier to buy one but it was enjoyable making it.

you'll love the AK-47 version
I've seen that too but it didn't seem to be that much more rounds. plus the loading took longer with the AK and that would be a factor as downtime is cooling time, that poor AR had very little cooling time.

Plus it wasn't designed by a communist.
 
properly staking is the way to go

Thanks, I spent an afternoon making a staking tool that supports the carrier on all sides while a hardened pointed screw presses metal into the sides of the screw heads, very similar to Brownell's.
I had more trouble finding a cone pointed set screw than making the holder, and eventually altered two 5/16-24 socket caps screws by turning a 90 degree point on the ends and hardening,then tempering them to a straw color. These screws have tine 1/16" diameter flats on the ends so the metal gets pushed aside as well as in.

It seemed to work well. :)
 
By the way, that was last weekend, this weekend I've spent making sears for Astra 4000 Falcons, 4 of them, out of S-7 tool steel.
I won't likely live long enough to find people who need the three extras I made as the Falcon is kind of a rare pistol. I'll leave a note to send them to Bob's or First's if no one takes them before then.

But what I'm learning is that all those little tiny hardened parts in firearms are intensely difficult to make, because they are so small it's hard to hold onto them. Plus they have to be just right.

The people who made the originals were mostly people off the streets with no metals skills. They were made in fixtures so none was needed, a few good tool makers kept the fixtures in good condition and little hand millers were run one operation at a time all day long, then handed to the next guy who sat in front of his little hand miller for the next operation.

I'd love to see how they were made but I think that's about right, from old films of gun making on youtube.
The guy who makes short runs of P08's in .45 ACP must be an exceptionally good machinist I think.
 








 
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