I know this is gonna sound weird...

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!

 

Interesting concept about indexing your sabots so one land is solid on each petal. Never heard that before.

 

I have some Clear looking Sabots sitting here beside me as i type this (.54 Cal, Hornady I believe?) With XTP Bullets in them. I have been wanting to try them, but always end up doing other things

 

I get about a land and a half per petal if I center a land.
Cleaned some 300 grain XTP's and shot my smallest 10 shot 100 yard group. 1 &13/16 ths. Previous best was 2 inches. This is with an aperture sight.
I've found indexing worth the effort. Cleaning apparently too. Its a small effort to make.