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a couple of plastic milk bottles filled with water are much cheaper and will show you similar thing.....
the same comparison has been made with .30calibre subsonics of different weights...if 150s...

woods223 those load levels sort of suggest that your red dot is on par/plurry close to, trailboss..eg a 4-5 grn charge is right on the sound barrier with 55grn pill.
Ive got as50n here too.........

right...the headshoot thing has been mentioned more than once on here..... its a rabbit and a .22lr you dont need to headshoot its a massive projectile for a small animal,chest shots kill pretty...

as you will have noticed most of the loads shown in last few posts are still well above subsonic levels... you are getting down to a stupidly light charge of powder to keep it below speed of sound.

well I suggest you try starting with your tightgroup loads you have hard data for....
your AP70 isnt a world away from trailboss so there is possibly data out there for it....definately is the...