I cycle 1145 fps regularly through my Beretta 390 12 and 20 gauges. Cole gun also sells a "spring set" which can quickly be swapped out for even lower fps (and frankly for the really fast 3 inch shells as well.
I have cycled 3/4 ounce shells on my 12 gauge with the standard spring. I have maybe 3-4k rounds through that gun, so it is just broken in
