From the 2010 review I did on the B&P slugs:
Last week, I wrapped up a 4 day shotgun course in which I shot approximately 200 rounds of B&P slugs (out of nearly 750 rounds of 12 gauge loads). Using my SLP Mk1, I did see early on failure to fully cycle issues after the shotgun had seen about 150 rounds earlier in the day. I was using the less than 1.5 oz piston. A quick cleaning/lube in the piston area got it back on track. I've no doubt that the 1200 FPS and 7/8 ounce weight is the main reason for this performance. On the accuracy side, I was getting solid 100 yard hits, off hand, on steel and fairly good performance out to 150 yards. At 200 yards, it was starting to act more like an artillery round....once heck of an arc to get it on target.