Recently I noticed that I was getting carbon smudges on my targets, around the edges of the bullet holes. I thought this meant I was getting gas blowby around the sabot. I was shooting an older box of 250 grain 45 cal XTP's and they were a little dirty. So. I cleaned them with rubbing alcohol and the smudging went away AND accuracy improved! I tried the same thing with my 45 shooting 200 grain 40 cals. They were clean, but accuracy was improved. Put 6 into an inch at 50 yards. Was zeroing an aperture sight. It seems that a dirty bullet or one with some oily substance on it, does have a negative effect on accuracy. The improvement was about a half inch at 100 yards and about the same from the 45 at 50. I also index my sabots so I have one land solid on each petal. Little things do make a difference!