[N310toN170]

So, I'm looking to have my can thread on to a barrel that is only .532" inches in diameter. Means I can't thread it to the standard 5/8" x 24 TPI and am gonna have to use 1/2" x 28 TPI and get an adapter.

Does anyone know where to get such an adapter?

My initial search lead to Tactical Innovations but I'm not into paying $60-70 for such a simple request. I could have a local machinist do it for $20 and a beer but he's kinda backed up right now and I am needing it to be very, very concentric.

Ideas?