I shot a prototype .40 Knight 500 in the M5 match . Conditions were not that great ( a bit windy ) My score was 238 out of a possible 250 . I can not say i shot the .40 that much better than a .45 . With my .45 Knight 500 shooting a 300 grain bullet I have shot scores in the 240s . But... I was able to shoot close to the same score with a .40 and a 250 grain bullet .
40 vs 45 they both work and work well . It is just a personal preference.
My Knight 500 is a 1-16 . I have shot 275s,300s and 312s . They all are stable with this 1-16 twist at 100 yards . When I get time I want to shoot all those bullets at 500 yards . I am very curious if the 16 twist gun will handle the heavier and higher BC bullets beyond 100 yards . The 312s leave the muzzle at 2250 I think they are down to 1500 FPS at 500