Originally Posted by brixx
if you have a gbbr m4 with 450 fps. If you use a .36g of bbs will it lower the fps into around 350fps?
If your rifle shoot 450fps on the chrony using 0.20g bb, and then you change to a .36g bb and chrony it again, you will notice a drop in fps. But the joules will be the same at the muzle. Your gun won't be field legal.
Set your rifle at 400fps using 0.20g then put whatever BB you want in it. (for outdoor use...)
In GBBR, heavyer BB will also give a little more fps, because of the gas expention, compared to a piston rifle, where the gas is unpressuried and just pushed by the silinder. So I'd chrony it again with the new ammo and check with a table convertion to verify that the joules output is still field legal.