14 February 2010
Your linotype bullets are likely harder than the 160.5 grain RCBS GC that I have been using. Therefore, if you use IMR 4350 powder you should be able to equal or better the velocity I achieved with that powder. 42 grains of IMR 4350 gave me about 2220 fps with good accuracy. 43 grains of IMR 4350 gave about 2275 fps with excellent accuracy. When I upped the charge to 50 grains of IMR 4350 the accuracy was -- well there was none. Groups were more like patterns at 50 yards. Several bullets yawed badly, although none completely keyholed. Velocity was about 2560 fps, but what good is that if you shoot 10-inch patterns at 50 yards?
In my opinion you should be able to get up to 2200 or 2300 fps with good accuracy with your 170 grain GC bullet. However, you may or may not be able to do that with IMR 4064. You may need to use a slower powder, such as 4350. Part of my reasoning is the relationships of powder, pressure, velocity, and strength of bullet. Explaining this is something I will leave to others much more informed on the subject than I am.