AR Sponsor
Posted: 11/25/2007 9:49:42 AM EDT
| I have a 20" post-ban barrel that I would like to put a flashhider on. What are the proper dimensions to cut the barrel down to prior to threading? I need the diameter and length of the turn-down on the muzzle. The threads are 1/2 x 28, correct? Anything else special to know? I have a friend who is a very good machinist, but he's not a gunsmith. Thanks. |
|
I am a machinist and did mine a couple of weeks ago. No big deal for your friend. 1/2 -28 is correct, so turn it to .002-.004 under 1/2 inch and thread. The length depends on the hider you're going to use. I put a vortex on mine , so had to cut a .075 (if I'm remembering right) long step behind the threads. The vortex has a slight counterbore. Mine turned out pretty nice. BTW, I don't know what kind of material your friend is used to working with, but my bbl was harder than hell. He'll have to run it slow. (he knows) Good luck |
|
Shooter62, Thanks for the help. I am planning on a standard A2 birdcage for now, but I am leaning towards a PWS FSC556 eventually. I figured the shank length would be the same for most muzzle devices. I didn't realize they varied. Do you now what the standard length is for an A2 flash suppressor? The barrel in question is a standard Bushmaster 1:9 chrome-lined. |
|
The A2 birdcage in my stash measures .745 inch from the end that contacts the crush washer to the bottom of the threads. If I was doing mine for it I would thread it .750 long and then try the hider. These ones have to be indexed so the part that isn't cut out goes down. I'd want my bbl to contact the FH at the END of the bbl. so the way I'd do it is to cut a thread relief on the bbl at the end of the threads, then face the bbl end off a little at a time until the FH indexes where you want it. (maybe a hair before) Make sure your friend does the last facing of the bbl length from the bore OUTWARDS. That's how they are "crowned" to insure no boogers disrupt the bullet on it's way out. This is just how I would do it, I don't like the idea of a gap between the end of the bbl and the flash hider. I don't know how the professional AR smiths do it. |
AR Sponsor