On the S400/S410 the pellets slide across the breach o-ring because it's in the breach area of the barrel rather than on the bolt. My guess is wadcutters would rub this area in a little harsher way, but then wadcutters aren't going to group all that well at much above 600-700fps, so you're looking at roundnosed pellets from many PCP's anyways. Even my 12fpe S400C will spit them out pretty fast, mostly beyond wadcutter accuracy. There are some heavy wadcutters like the RWS Supermags that may slow the gun down enough to group well, but they'd still drag across that o-ring. JSB Exact roundnose pellets group beautifully in my S400, you only get one hole anyways, why use a wadcutter and make it bigger:)
As for the first PCP debate....I've owned two Chinese PCP's, one FX Black Widow, one TalonSS, one AA S400C, one Korean Career 707 II, one Korean Sumatra Carbine. So far the Air Arms guns are tough to beat. I have shot quite a few others and as far as repeaters go I really like the biathalon cocking on the FX Gladi8tor, Cyclone, etc....... The Air Arms repeaters I've shot I didn't find incredably smooth, but the single shot version I have is really smooth. The new side lever S410's might be pretty smooth and easy to handle, but I haven't shot one....yet!
Pump or bottle depends on a few things like how much you shoot, your general health, etc.... I pump and don't mind it at all, but then I don't shoot 2000 rounds everyday...I'm more like 100 rounds a week at most.
