I've used two solely for work for about seven years now, both in .177, I cannot fault them, thousands and thousands of trouble free shots. No mag problems.
Only gripe I had which I was talking to BSA about them was the rediculous little [BANNED TEXT] screw that was supposed to take the weight of the gun on the foreward sling swivel. It gave way in the middle of the new night in the middle of a very sheety dairy cow yard, it along with £1200 worth of NV hit the concrete really hard.
Thankfully other than the sh1t nothing was too badly damaged.
Awesome bits of kit.