Semi - Curious; did you shoot the mmp sabots first then the harvester? If that's the case it looks like you had a continuous drop in velocity from the first shot to the sixth (excluding #5). Seems to me it would have been just the opposite as any fouling would have generated more pressure which would increase velocity.
Also, I am wondering how consistant the powder charge was. Were they weighed out or volume measured? Sorry about all the questions. Its just my curious nature. The 144 fps from the first to the last shot is quite a difference. Almost approaching 10%.