For a lark, I decided to try some of the 19gr swaged ammo from Nick & Co. in my ASP20.
I can usually get "all shots touching" 5shot groups at 25 yards with JSB 15.89gr pellets.
One complaint about this gun that I have is that is is very hard to load anything but JSB. I couldn't get a baracuda to sit flush in the breech. However, the 19gr .217 slugs dropped right on, and kept going about a quarter inch - well into the breech. Super nice.
Then I took 5 shots at 25 yards. The first group scattered about an inch - maybe seasoning the barrel?
The next 4 shots all went in the EXACT same hole, but the 5th drifted a bit to the left - pretty sure that was my fault.
I plan on doing some more testing once I put footwear suitable for an icy march, so I can trek out to the target zone and get some fresh targets and pictures. I'll also get some chrony numbers of these slugs. Trying to curb my excitement, but this looks like it may be a squirrels worst nightmare!