Max loads and HT'd boolits

[Marlin Junky]

Given a maximum load in the 30-30 with a 14 to 15 BHN RCBS 30-180-FN if one were to HT said boolits to 20 to 21 BHN, would he need to back the charge off in order to keep the pressure constant and if so would the velocity remain the same?

MJ

[imashooter2]

Veral Smith says the pressure will go down with the harder bullet because it will obturate less...

[Marlin Junky]

Then I would actually get more velocity with less pressure when changing the boolits temper; i.e., heat treating from 14.5 to 20.5 BHN?

MJ

[Bass Ackward]

Then I would actually get more velocity with less pressure when changing the boolits temper; i.e., heat treating from 14.5 to 20.5 BHN?

MJ

MJ,

Maybe, with slow enough powder. But you can't assume that. This past weekend I was shooting squibs in my Whelen using 4759. I could raise velocity or decrease it by 100 fps just by seating into the lands vs allowing a small jump. So pressure was raised by the resistance to forward motion vs bore friction. A full charge of 4759 in this instance, and I would have had a problem. And this is a bolt.

Hardening a bullet that needs to size down in the throat may make a difference you will never notice or it can bite you. Remember the safety rule, change anything, start low and work up. Your buddy is doing it right.

[44man]

Bass is right! Anytime a max load is used, any change to anything from primer to seating depth means a new workup. If you were shooting a moderate load, you would not be concerned too much but accuracy might change a little. Max loads are very seldom accurate anyway. I have had rifles using jacketed where a little over max shot best but I have never seen it with cast. In some of my revolvers, max is more accurate though. Depends on the gun and all components.
Always play it safe.

[Larry Gibson]

Given a maximum load in the 30-30 with a 14 to 15 BHN RCBS 30-180-FN if one were to HT said boolits to 20 to 21 BHN, would he need to back the charge off in order to keep the pressure constant and if so would the velocity remain the same?

MJ

By "maximum" do you mean for the cartridge/rifle or for accuracy with that cast bullet? Two different "maximums" with rifle cartridges most often as most "maximums" for cast bullet loads are not near the "maximum" pressure wise for the cartridge/rifle. The 30-30 can be an expception though.

Larry Gibson

[Marlin Junky]

I'm glad we're clarifying maximum because I meant my maximum which means a load that produces the best accuracy I can obtain in a given rifle, with a given boolit/powder/primer combo, with the most pressure/velocity generated before I have to FL size more often than every three reloads. Not having any pressure equipment, finding my max load is more of an art form than a science so I use the number of reloads fired in a lever action before I need to FL size my brass so the levers snap shut easily.

MJ