Totaidla , I’ve ’run test showing how hard you hold the rifle to your shoulder effects velocity. Not so much total velocity but rather higher ES/SD . It showed a load that had an ES in the high 20’s with firm shoulder hold went to a 12 ES with free recoil . I’ll add this was with a heavy-ish rifle of about 12 to 15 lbs with a muzzle brake which made it easier to let it freely recoil and catch it . Not sure I’d try that with a 6lb rifle with sporter barrel .
I have the exact numbers somewhere in my notes if you all want to see them . The test helped me out a lot back when I never could get my SD out of the teens . Changed how I held the rifle and started seeing more single didget SD’s . I actually ran the test live here on the forum and posted the results in real time . It was a few years ago and was not in a thread I started so I have a hard time finding it .
It was Bart B that gave me the idea to try the test . On several occasions he claimed rifle hold could effect velocity and like most I thought “yeah right” what ever . Then I figured it’s an easy enough theory to test , it doesn’t even take any real extra effort on my part . Just take an established load I know shoots well and consistent. Then shoot it over a chrono with different holds on the rifle . I encourage any and all to try it . Do an honesty test and see for yourself , just keep in mind when you’re letting your rifle freely recoil it could be dangerous .