On a side note, here's a hypothetical. You try this new powder. 7-08, 120 ttsx. You are not seeing any pressure sign. Velocity is very high and you are not near max. Exactly what velocity do you stop at?
Basically what Smokepole said. I'd look at as many sources as i could for that bullet,and even others of the same weight noting barrel lengths, etc. I'd likely back off to to roughly the top velocity,give or take. Watch accuracy.I'd be looking for a weighted average in terms of velocities and consider anything I didn't see in a manual as an aberration or goof up on my part from going too high....kind of an "OOPS!".
I'd take 5-10 cases, fire them several times,and watch velocities and check for primer pockets opening. If the load passed all these touch/feely tests I'd say I'd be good to go.Not the most scientific of methods but maybe the best we can do as basement hand loaders.
I'd also compare powder capacities of cartridges a step up, in size....say a 280 and 280 AI in the case and see what they are doing.If I am equalling or exceeding the velocities of those cases I'd be looking for the reason.
