Quote Originally Posted by Capt. mike View Post
Rumbler any idea why in most of the loads I can find all the plated and lead loads call for powders like accurate #.... V-3N37, R silhouette, ect but the jacketed loads have all the Autocomo, blue/green/red dots, titegroup, universal, 7625. Ect. Is it the burn temperatures or something, I just run what I brung and Im down to my limited supply of sr4756 but Ive been able to kind of wing it and have loads that worked great with everything from 115 9mm, 135 and 180 .40s, to 230 ball for .45

I wish I had a way of testing my theory, I would love to.

But I believe that it is a combination of burn rate and pressure.

Remember that smokeless powder does not "explode" when ignited, it changes from a solid to a gas. So there are actually two factors to be considered in that process; the speed at which the conversion occurs, and the volume of gas created.

A "fast" powder may very well convert to gas very quickly, but not create the volume of gas necessary to propel a bullet at very high velocity. The net effect being; lots of heat and a slow(er) moving bullet - obviously.

. . . but just when one says "dang! That makes sense!" Rumbler says; hey there are fast powders out there that make a LOT of gas, and there are "slow" powders that make a little gas and some that make a lot of gas.

Bottom line is that a jacketed or coated bullet tolerates heat and pressure better than a "raw" lead bullet because of that coating - be it copper, brass, or some synthetic hi-tech chemical.

Thus lead bullets tend to like powders that have a slower solid to gas conversion rate so the bullet can get farther down the barrel - away from the heat caused by conversion. But is it also worth considering a very fast powder that produces a lower volume of gas - and I am sure you are seeing why: once the conversion process has occurred the heat generated has peaked - it is not going to continue to rise. Even raw lead can take surprisingly high extremely short duration heat.

Selecting - wisely and safely - the best power to use for a given barrel length and bullet weight is where the art in reloading is to be found. It is my seldom humble opinion that only time and experimentation creates reloading artist.


. . oh, and some "luck" can be handy to have too.