I saw on the Nosler website were they had a 257 Roberts load with the 110 gr. Accubond rated at 3075 fps. My 257 Rob. loaded with 48.0 gr. or RL19 under a 100 gr BT only gives me 3000 fps over my chrony. I would guess you are maybe running 2850-2900 fps. I haven't given the Accubonds a try but I did give up on the 100 gr. BT's because of poor performance on whitetail deer and feral hogs. I switched to the 117 gr. Hornady BTSP over H4831 with a MZ of about 2900 fps and good accuracy. I've tried the Accubonds in my 280 Remington and like them alot. I haven't run across a box of the 110 gr. in my area.

I'm sure you know that most manuals load the Roberts anemic even with what they consider +P loads. The only manual I have that loads to the Roberts velocity potential is the Barnes manual in my opinion. As always use safe loading practices watching for pressure signs and have fun. I'm glad to see someone else using the 257 Roberts.