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To the OP...clamp on adapters are a very bad Idea as the OD of the barrel is pretty much never concentric with the bore. Trust me on this. I have threaded several thousand barrels and run out of .020 or more is common.
Baffle strike "ouch"
Use a brass shim, aluminum shim (flat, rolled,thin) or some softer metal than the gun barrel under the adapter for the set screws to be applied against. Or, make sure your set screws are either brass tipped (crimp a cap on them if needed) or Delrin, etc..
I have done this on my Big Bore PCP air rifles wherein the barrel muzzle was not threaded.
As to proper alignment, use a brass rod longer than the can and machined to fit tightly in the muzzle, with tapered or straight.
That is your option other than a threaded muzzle or muzzle can attachment similar to the AR variants and Sniper rifles have which are threaded on the barrel muzzle (i.e. the muzzle is already threaded!) to begin with.
Last edited by 1Forecon; 02-17-2020 at 03:58 PM. Reason: Spieling!
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