I'm being pretty loose. I got a girl running a SA17 with remote and 50 rd hopper, I run a 8" barrel plus silencer on my TPX with 3.5 oz remote. I would like to say no more then a 50 rd pocket hopper (they really only hold 40 if you want them to feed) for feeding. no stock. as soon as you add a stock aiming becomes "rifle" like.
barrel length doesn't matter.