My standard tm mp7 will fire over 1j with 0.28g on any green gas or abbey ultra, i have even had it fire over 1j on abbey 144a on hot days.
Cutting down the rocket valve spring will lower the fps, there is a older post on these forums in the gas guns section called
tm mp7 maintenance and tinkering which has a link on the 2nd page to springs you can buy on amazon that will fit the
rocket valve rather than cutting down the orginal spring.