I'm involved in another hobby which is custom air rifles. Currently, we're dumping a good volume of 2000 psi air at a .22 caliber pellet.
Last meter results show about 22 ft lbs of energy. However, we used a .22 LR barrel blank. I recently learned that .22 LR barrel rifling is far more aggressive than .22 air rifle barrel. .22 LR rifling doesn't allow the pellet skirt to fully engage the bore and air escapes around the pellet. Reducing velocity. Sure enough, that's what's happening.
So... rather than picking up a plain old Lothar Walther air rifle barrel, I thought I get some thoughts on a .22 polygonal barrel for use in an air rifle. Would a polygonal barrel be more likely to allow a pellet skirt to fully expand and create that tight skirt seal?
The bores on the air guns are tighter. They make the swagers to size your pellets to bore size. The poly rifling would be more gentle but I'm not sure if you would get quite the engraving, minimal as it is, to get the job done. Of course turning a blank down would be one heck of a chore.LOL
Good luck on it and keep us posted.
PS: I'm shooting a 22 cal. TechStar(BSA) that runs a 3200 , yes 3200, PSI supply. ME runs right at 34 ft. lbs. with the Crow Magnum pellets. It will do under a dime at 50 and has enough spunk to make a gopher DRT at 75 yards all day long.
The best firearm for self defense? Any loaded one will do.