Monday, March 15, 2010


...I'm going suppressed. I just embarked down the long road to NFA item ownership, and I'm setting up one of my rifles for that purpose. I've got an old K-31 for which I want to start working up a nice 200-220gr. subsonic load, which I figured would be a really neat conversation starter at the range. I needed a way to attach a quick-detach mount for the can, though, so I started asking around to figure out which way to go. Originally, I was going to just have the barrel threaded for the AK-style mount (14x1mm LH), since the bayonet mount is .550", but I didn't think I'd be able to get the threaded portion long enough, and I was concerned about shouldering the mount on the front sight base. So, I thought, move back the FSB and cut/thread/recrown the barrel, right? Well, I figured that'd be an awful lot of money to spend on a $100 rifle, but I might end up going that way in the end. Instead, here's what I did: I got a slip-fit adapter from Brownells that was .556" ID stepped to .345" ID, and had the AK thread on the business end, leaving me with a .003" radial slip-fit clearance with which to deal. If this thing was cocked .006" on the muzzle end, that would mean something like .093" on the exit of the suppressor. Unacceptable!

Then, after consulting some of the local Highpower guys (who mount shit to their barrels all the time with pretty close tolerances), I had a machinist make me a brass stepped pilot that would be a very tight slip-fit in both the barrel bore and the AK Thread Adapter (0.296" to 0.346"):

Then, I simply used green locktite (sleeve retainer) to take up the .003" radial clearance, and secured the set screws in place with red locktite, and let it set up for a few days before removing the pilot, which was difficult to get through the adapter with it's slight taper! I then mounted the YHM AK Thread QD mount for their 762 Phantom series suppressors, and here's a down-the-throat look at the pilot centering the whole contraption in the bore:
Here's a side shot of what it look like:

I'm figuring on having the can stick out 8.5" from the base of that flash hider, which will make the overall rifle (well, carbine technically) length 54" from butt to can (oooh! double entendre!). Anyways, It's going to be a long wait I'm sure, and I might get cold feet and just send the barrel out for the original FSB move/cut/thread/recrown operation, but if this doesn't seem to move around at all over the next few hundred rounds, I think I'm good.