Thursday, September 17, 2009

A quiet K9

Between "real" work, we get to do some funky stuff here. Sometimes it is for a valid reason, other times because we feel like it. This project is somewhere between the two.

We undertook to build a semi-auto carbine out of junk we had laying around the shop. Mostly to see if it could be done, but at the same time we had planned on entering a homebuilt gun contest. The "valid" reason was that it would give Earl a chance to practice his skills on the ancient South Bend lathe that is one of the main workhorse tools in the shop. (I need to mention that we started this project when Earl was new here, it has been sitting around for a while)

We used leftover AK47 parts (hammer, safety, trigger, grip), an Uzi carbine barrel, a Sten magazine and magwell, and the rest of the parts that went into it were home made. To make a long story short, it worked.

We named it the K9, K for Kathan, Earl's last name and 9 for 9mm.

Earl is pretty quick with his trigger finger, here is a video of him trying it out:



But, the story gets even more interesting.

We decided to silence it. Why? Because we wanted to see if we could.

I had to send off a Form 1 to the BATF to get permission to build the silencer. It took months to approve, but if you have no felony record you can get approved. The BATF is actually quite accommodating when it comes to stuff like this.

With the approved Form 1 in hand, it was time to build the suppressor. A series of holes were drilled in the barrel to bleed off gas, thus slowing the bullet down. A stack of fender washers was fitted over the barrel to act as baffles that will contain the hot gasses and give them a chance to cool. A piece of tubing from the McPherson strut of a Jeep Cherokee was fitted over the whole mess. Done.

It quiets the gun down considerably, but the 115gr 9mm ammo that I have on hand still breaks the sound barrier. The sound doesn't seem to come from the gun though, it seems to come from downrange. I've ordered some heavier, 147gr ammo that should be subsonic and it will be interesting to see (hear?) if it quiets down to the level that I think it will. When we get the 147gr ammo in, I'll film it and post the results here.

I'll have to get a picture or two of how the contraption looks with it's silencer on it too. It is ugly in a cool sort of way.

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