Regarding pellet sizing, early seventies into early eighties we did not have the advantage of pellets supplied from the mfg,s with different size heads in 177 that i remember. Much like the .22 and .20 nowdays. Also the quality of the pellets being produced now are are way ahead of the production of that time period. I used to use a sizer back then. Yes, it did make a differance on my equipment of that time period. Currently I do not see any improvement groupwise, other than weeding out deformed or small dia. heads from 500 count tins. In this respect it might be useful as trying to mike those little pills is a pita. Don's sizer also made the skirts very uniform which probably had more effect than the head dia. Equip. of the time was spring driven or single stroke pnumatic, co2 was coming on strong, more as a way of reducing shooter fatigue from cocking. Velocities ranged from 425 to 575 fps apx. At the time it was determined that the best velocity, for 10 meters with a apx. 8gr pellet, was in the 525-550 fps range.