that was my thought about power ie if blowing back through the breach past the o ring then there would be a drop in power. obviously aware the power goes up with the heavier the pellet. however tested on bisley mags and when got home put the new h&n baracuda hunters through it. they love my steyer and are accurate so would like to continue using them. they are tight in the steyer but seemed to fit the 200 fine. just had another look and feel of o ring and feels a bit hard. maybe needs replacing as not sealing that well. assume rifle must be pre anti tamper. if this is case may have to be a bit careful when replaced as it may be over the limit. anyone any other bright ideas?