As of late, we've done quite a few muzzle can installations for folks. Some go really well, some don't.
Manufacturer's typically include a print of the thread pitch and length when they sell a can. The class of thread becomes an issue sometimes.
Recently we did one for a guy who did everything right. He supplied all the parts and included the print. We ran our threading cycles until the pitch diameter matched with the class of thread listed in the print. Values were taken directly from the machinery handbook to determine the pitch diameter ranges.
Box it all up and send it back. Get a phone call. The can doesn't go on all the way.
Taper in the ID threads or a slight variation on the pitch diameter in the can.
This doesn't happen all the time, but it does happen.
Here's what I'd offer you in order to avoid this.
If at all possible, send the can with the gun. It does require additional effort on your part, but anything worth doing is worth doing once. Right?
Second, if that's not an option see if your can has an adapter piece that's removable in the back of the can. If it does, mail that piece by itself. This way the smith can fit it and no drama with paperwork is involved.
Other peripheral things we like to try to pay attention to:
Some can manufactures insist on not counterboring the threads in their stuff. They don't realize the issues that come into play for the end user/smith that has to install it. Undercutting a thread on a muzzle is just poor workmanship in our opinion. The presentation is destroyed when this is done. If the threads in the can are started just a bit deeper, say an 1/8" inch it allows us to thread to the shoulder and be done. What I am saying is if at all possible buy a can with a counterbored thread lead. Your smith will thank you for it.
When practical, we've actually gone in and modified the can ourselves. Usually only with local folks though as the regulations doesn't lend itself to shipping these things all over the creation.
Hope this helps and good luck.
C.
