2 cell LiFe battery - though this might be starting to struggle cycling from still
7.4v Lipo (8.4v fresh off charge)
6.6v LiFe (7.6v fresh off charge)
Other than that fancy mosfet or burst mosfet or plug/play avacado
Or a very high torque 28tpa motor or above = frankentorque - that will be slow rps
TBH - can't see why you are worried too much
Gunfire tested a LCT STK-74 on 7.4v at 416fps shooting just over 600rpm
So if some others are saying 1,000rpm what fps & what battery are they using ???
go to 2:00 for chrono stuff
most stock guns shoot about 12/13rps out of box on a 7.4v
some shoot a bit quicker if they got a quicker motor
(say 15rps on 25k motors with average 7.4v)
if you got a clip of it shooting quite quick I'd check they are not running it on 11.1v
Often UK spec guns, a 7.4v will often do a lightly tweaked gun to get to 20rps
but stock/average performance most guns will struggle to get 15rps out of box 7.4v