The powder is limited to 250grn bullets and lighter because of pressure. The powder is creating alot of pressure. I would not push the limits to much with out finding out more info. I wouldn't trust the sabots either. I never thought that was a reliable way to read pressure.

Like GM said, a 52caliber would relieve some of that pressure. A 45 would just increase it.

Another nice thing about BH209, it works on less pressure thru the bore then 777 of equal volume.