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Posted: 2/18/2016 8:27:18 PM EDT
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I've decided to build two cans soon, one for .223 and one for .308. I will use the direct thread kits from SDTA or DM to save money.
I pulled the flash hiders off of the two rifles I plan to use the cans on and was dissappointed that the threads don't go all the way to the shoulder of the barrel. There is an unthreaded portion about 1/16 to 3/32 long which will prevent the cap from seating tightly against the shoulder. I guess this is no big deal if a crushwasher and a2 fh are being used but I think they messed me up for using a direct thread can. The .223 barrel is from BCM, you know how much they cost, and the .308 is from a $1,400 CMMG. So is this common? Some kind of washer for the solution? |
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Advising against any sort of washer or spacer of any sort, I would simply get both of the barrels re threaded by a qualified gunsmith.
Some members may use spacers or the like in certain like situations and are successful, I avoid it. Potential baffle strikes are no joke. |
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Don't use normal washers or AR crush washers or Peel washers with a suppressor.
Sounds like you need a precision threaded spacer which is counterbored on one side to accept the non threaded area where the threads end before the shoulder. Another option is to have the area at the shoulder undercut to the thread minor diameter. |
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Advising against any sort of washer or spacer of any sort, I would simply get both of the barrels re threaded by a qualified gunsmith. Some members may use spacers or the like in certain like situations and are successful, I avoid it. Potential baffle strikes are no joke. That sucks. The last thing I want to do is pull my new rifles apart and send the barrels off. There goes my direct thread savings. |
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Don't use normal washers or AR crush washers or Peel washers with a suppressor. Sounds like you need a precision threaded spacer which is counterbored on one side to accept the non threaded area where the threads end before the shoulder. Another option is to have the area at the shoulder undercut to the thread minor diameter. Yeah, I mean how hard is it for the barrel maker to do one more step which would face the shoulder and undercut/rebate the last 1/16th. With all the interest in suppressors these days, you would think it would be done as a matter of course. I looked at the threads on my Ruger 22/45 and a Faxon barrel I have, they both are as I described. |
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My Griffin brakes have a thread relief that is about 3/32" deep to compensate for this. I'm guessing that it is common to leave the relief out since most barrels are profiled and threaded on a CNC lathe. Does anyone know if the "griffen" brakes sold by SD Tactical have the thread relief? |
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Don't send off your barrels to be cut and threaded just for that! If the flash hiders aren't relieved send them to me and ill add the relief. Some barrel thread specs call for a relief, and some to a shoulder. The flash hiders fit fine because the crush washer is thick enough to make up for the missing threads. With a can, the end cap should bottom out on the shoulder without any washer. At least, that is my understanding. |
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The flash hiders fit fine because the crush washer is thick enough to make up for the missing threads. With a can, the end cap should bottom out on the shoulder without any washer. At least, that is my understanding. Quoted:
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Don't send off your barrels to be cut and threaded just for that! If the flash hiders aren't relieved send them to me and ill add the relief. Some barrel thread specs call for a relief, and some to a shoulder. The flash hiders fit fine because the crush washer is thick enough to make up for the missing threads. With a can, the end cap should bottom out on the shoulder without any washer. At least, that is my understanding. So threading to a shoulder full thread depth is impossible because of the angle of the cutting bit, so no matter which type of thread you have, wether it aligns and indexes off the muzzle or the shoulder of the barrel, the muzzle device will usually have a releif cut. This thread is cut to the shoulder, the muzzle device still has a recess and aligns on the shoulder. 
I chamfered the shoulder so I didn't crash the tool, but this would normally be square to your muzzle. 
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We relieve behind the threads on our barrels for the very reasons mentioned. Allows for the use of non-timed muzzle devices and suppressors that do not have a chamfer at the threads. Just bought a Faxon 16", midlength, pencil for a build for my wife. It's really nice and the threads are exactly what I wish my BCM came with. Keep up the good work. |
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So threading to a shoulder full thread depth is impossible because of the angle of the cutting bit, so no matter which type of thread you have, wether it aligns and indexes off the muzzle or the shoulder of the barrel, the muzzle device will usually have a releif cut. This thread is cut to the shoulder, the muzzle device still has a recess and aligns on the shoulder. http://i67.tinypic.com/69jlmw.jpg I chamfered the shoulder so I didn't crash the tool, but this would normally be square to your muzzle. http://i63.tinypic.com/24fxmr8.jpg http://i65.tinypic.com/24qsp6o.png Quoted:
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Don't send off your barrels to be cut and threaded just for that! If the flash hiders aren't relieved send them to me and ill add the relief. Some barrel thread specs call for a relief, and some to a shoulder. The flash hiders fit fine because the crush washer is thick enough to make up for the missing threads. With a can, the end cap should bottom out on the shoulder without any washer. At least, that is my understanding. So threading to a shoulder full thread depth is impossible because of the angle of the cutting bit, so no matter which type of thread you have, wether it aligns and indexes off the muzzle or the shoulder of the barrel, the muzzle device will usually have a releif cut. This thread is cut to the shoulder, the muzzle device still has a recess and aligns on the shoulder. http://i67.tinypic.com/69jlmw.jpg I chamfered the shoulder so I didn't crash the tool, but this would normally be square to your muzzle. http://i63.tinypic.com/24fxmr8.jpg http://i65.tinypic.com/24qsp6o.png Ok, makes sense that it would be difficult to thread all the way to the shoulder due to the v shape of the threading tool. That's why barrel makers should make a relief cut. I guess in the end, I'm just surprised that my two not inexpensive rifles from reputable manufacturers would have to have further work done to the barrels to use a simple thread-on suppressor. Thanks for all the replies. |
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I would expect better from BCM but I don't think they are making a claim to concentricity anyways so the assumption might be it will be cut and threaded to the better spec if necessary.
That's like rails going on crooked on their uppers. They make it to whatever spec and they don't strive for perfection where it doesn't matter (in their eyes). They tightened that up, I believe, after a few complaints went vocal. |
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Just bought a Faxon 16", midlength, pencil for a build for my wife. It's really nice and the threads are exactly what I wish my BCM came with. Keep up the good work. Quoted:
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We relieve behind the threads on our barrels for the very reasons mentioned. Allows for the use of non-timed muzzle devices and suppressors that do not have a chamfer at the threads. Just bought a Faxon 16", midlength, pencil for a build for my wife. It's really nice and the threads are exactly what I wish my BCM came with. Keep up the good work. A high compliment. Thank you! |
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