It is pressure rather than velocity which dictates the need (or not) of gas checks. I shoot mostly a load of 9.5 grns of Herco with unsized, Lee liquid lubed 150 grn cast bullets from my Model 94. This produces around 1,400 fps with zero leading from my rifle. To get substantially more fps without leading you could try a reduced load with a slower burning powder. Reloader 7, H4895, W748, or similar choices for typical full power jacketed bullet loads would be worth trying. The Lyman manuals (regular or cast bullet versions) both offer numerous combinations with cast bullets and various powders. The 30-30 has proven itself to be one of the very best cartridges out there for cast bullets. Good luck with your experimenting...