Cast vs J-word CUP Pressures

[Wrbjr]

Got to thinking on this and it's probably been covered somewhere... but for two bullets of the same weight using the same powder... would the lead boolit develop more or less pressure than the factory type round? I guess it might have to do with friction? J-word vs lead..... any thoughts?

[44man]

It can depend on the alloy and boolit. Not to be taken lightly because you can go over pressure with cast.
In general, you will get more velocity with cast and some can use MORE powder then jacketed. OTHER BOOLITS CAN'T.

[Rocky Raab]

It's more than just weight, too. Diameter and bearing length are major factors in pressure. In general, a cast bullet develops less friction than jacketed, if all other factors are the same. Because it moves down the bore easier, a cast bullet travels a bit farther before the powder can hit its peak pressure - and therefore the pressure peak will be lower.

[Wrbjr]

It can depend on the alloy and boolit. Not to be taken lightly because you can go over pressure with cast.
In general, you will get more velocity with cast and some can use MORE powder then jacketed. OTHER BOOLITS CAN'T.

Good point, 44man..... these boolits are from Hunters Supply and are 5% Tin and 95% lead. BHN of 10, so I thought being somewhat soft it might be an issue. Trying to come up with a starting point using Power Pistol and slowly working a load up to about 1250 fps or so. The other factor is that this boolit is only 135 grains for a .40 S&W. Most load data starts at 155 grains.

[Wrbjr]

It's more than just weight, too. Diameter and bearing length are major factors in pressure. In general, a cast bullet develops less friction than jacketed, if all other factors are the same. Because it moves down the bore easier, a cast bullet travels a bit farther before the powder can hit its peak pressure - and therefore the pressure peak will be lower.

Rocky, after I got to your reloadingroom....all of your links within ended up with a 404 not found error. Is your site ok or maybe my version of Fire Fox is being cranky?

[44man]

Rocky, after I got to your reloadingroom....all of your links within ended up with a 404 not found error. Is your site ok or maybe my version of Fire Fox is being cranky?
Drives me nuts too. I also use Firefox.

[Wrbjr]

I guess I'll start with a tiny load, remove the squib and go up half a grain repeat til it actually fires and ejects properly to establish a baseline minimum load and velocity. Then take it to the velocity I desire and not worry about pressures.

[243winxb]

Start 7.3 gr power pistol, 40 S&W 135gr. Data here - http://www.stevespages.com/page8a.htm The 40 works at high pressure, be careful.

[Wrbjr]

Start 7.3 gr power pistol, 40 S&W 135gr. Data here - http://www.stevespages.com/page8a.htm The 40 works at high pressure, be careful.

Perzactly what I was looking for. Thanks! Will start low and slow.

[Rocky Raab]

Have no idea about my website, guys. Links work fine for me.

[Wrbjr]

Well, just an update on the Hunters Supply Pentagon HP cast boolits. 135 Grain.

With Power Pistol, the Chronograph puts these guys through the trap at approx 1250 fps or so at 7.5 to 7.8 grains. They feed, fire and eject well. Have put about 50 rounds or so through it while playing with different loads. Will do some fun shooting next week of different items for what I call Terminal Ballistic Eye Candy. Lumber, small propane bottles, water jugs, Wells Fargo Armored Cars ect ect. :coffeecom Hope to see some nice mushrooms.

[Wrbjr]

Have no idea about my website, guys. Links work fine for me.

Hmmm.... it must be Fire Fox.

[BAGTIC]

The most important difference is the difference in engraving force which causes difference in early pressure rise. Once a bullet is engraved to match the riflings there should be little difference.

The Quickload internal ballistics program offers the following guidelines. The force caused by bullet pull and engraving is approximately equal to the following (in psi):
Jacketed rifle bullets, 3625; solid soft brass, 1800; solid copper, 6525; jacketed handgun bullets, 2175; lead, 1160. Loading the bullet so it touches the rifling adds 7200 psi.

[popper]

bagtic - does QL state where the guidelines come from?
Loading the bullet so it touches the rifling adds 7200 psi. that is a lot.