The valve in an RT will recharge at around 20-22 times a second, so in theory thats the ROF they can achieve. but the downfall is the loading, unless you have a warp or a Halo you wont get too close to that, oh that and a chopping problem, but LvL 10 has put a stop to that.
I Had my RT with LvL10 fitted running with a halo B at the weekend and it ripped. had to easily have been firing in the high teens(it was like a orange rope flowing from my barrel
) no ball breaks and my foamy had gone missing
i love my RT
tb-303