6.8 SPC ladder results

I ran a ladder from 24 grains to 26 grains of IMR 3031 on 140 grain cast bullets in the AR15. The groups at the end tightened up vertically but not horizontally. I seemed to be getting right drift and not sure if its the bullets or me and the rest. It doesn't quite fit in the lead sled because of the grip hitting one of the adjustment knobs. At 26 grains I got 3 in the money and 2 drifted off. The first two were in the white and 3, 4 and 5 hit center.

Bullets are WW lead about a hardness of 11 and water quenched and about a 16 I think. They are powder coated and quenched right out of the oven again. using the MP 278-125 mold but my lead throws heavy and at 139 with powder and gas check on it. AR has a 1/11 twist and 18" Barrel.

Any ideas on the right drift? Use a different rest, powder, something different with bullets?
Attachment 325254

I believe that I would start with your rest. Sandbags or whatever to eliminate that as a reason first.
Does your rifle shoot factory loads well?

Sent from my Pixel 5 using Tapatalk