Currently shooting the 196gr NSA HP slugs at 750ish for 250FPE, started at 190FPE out of the box but was really hoping to get these things going closer to 975fps for around 400FPE. I've ported the transfer port and barrel, ported the exhaust side of the valve, enlarged the intake side as well, honed down the high pressure side of the valve stem,put a shorter and weaker valve return spring in, took some material out of and shaped the pellet probe, polished the barrel but haven't been able to get more than an extra 100fps out of the gun. Any suggestions? Maybe I should just get some 137gr round balls and shoot those and compare drop and accuracy to the NSA's. Anyone know the ideal speed of a round ball? Pretty sure their BC is poor.