Best gurus, I seek your thoughts. While working up a load for my 19.5" barrel .243 carbine, I loaded 16.5 grains (what my Little Dandy measure throws with a #20 rotor) of IMR 4227 power behind a SAECO gas check bullet, cast of linotype, weight 80.5 grains, with a magnum primer. The bullet was seated to contact the lands. This gave me 1884 fps, just about what I would expect. Moving on to the #21 rotor, throwing 17.3 grains, my chrono showed a velocity of 2179 fps. I was shocked that a 0.8 grain increase in powder would give 295 fps more velocity. Both loads are within Lyman/RCBS recommended ranges, and neither showed any pressure signs, but I still found the experience disturbing. Should I worry?