Re: 220 Swift Improved?????
SRHaggerty, MTBA'S prediction of 3600 with the 68 grain bullet is realistic, as in my 220 Swift AI I achieved 3,630 fps with the 68 grain Hornady in a 25.25 inch barrel.
However, my gunsmith achieved 3765 fps with the 68 grain Hornady HPBT using 47.0 grains of Norma 205 in my barrel, prior to sending it back to me after chambering. I had exhausted my supply of Norma 205, and could not access any more, but the other powders that were available in Oz in the mid 1980's could not get anywhere near that velocity.
I suggest you email Richard and get his view on the explosiveness of his 68 grain ULD bullet at around 3600 fps.