Interesting. Mk2 of mine shoots same numbers all day. Must be only a m3 -720 pp
Lucky you. But normally this issue is also in mk2 PP version. But it becomes significant only when the gun is set at low power. Like shooting 18.13 jsb pellets at low reg pressure and low hammer strike.
The heavy hammer strike over powers the extrusion issue and things look good.
It's all good as long as you are satisfied.