A challenge for the 7383 crowd

[Jim]

For those of you that use IMR7383, what charge would you start with for a 500 gr. round nose bore rider in a .45-70? The bullet would have to be seated to SAAMI specs to feed in a Marlin .45-70 Guide Gun.
I ran a bunch of calculations on load density for this and I came up with a starting load of 30 grains.

[Ricochet]

I'd steer clear of it altogether in the .45-70. I tried heavily compressed 7383 (something like 47-49 grains, I think) under a 340 grain cast bullet in my 1895 Marlin. Quickly locked the action with unburned powder tubules. Took a lot of work getting it cleaned out. Velocity was blackpowderish, something in the 1300s. And it stank most vilely of ammonia, which blows out the muzzle with more completely burned charges. I'll only use 7383 in bottleneck cases in loads where it burns fairly cleanly, and with some of the lighter of those loads I've still perforated the plastic over the readout of my Chrony with flying powder grains, and always had to turn it over to shake out the powder grains that fell in the top while shooting.

[Coastie]

I can't match the experience of some, but I would be careful compressing 7383. I have only worked with it in 30-06. . After reading and some testing (no chorony working at that time) I loaded Remington brass with jkt and pb 180 grain projectiles with various amounts of compression ((kept each group seperate) then broke down the rounds . In my limited "study" and with my powder lot I found that the greater the compression the more broken grains of powder and "powder dust" in the round. I believe that the broken grains and the "dust" are a part of the cause of the "spike" that some folks get with this powder. I like this powder and I'm not finish working on it, so would like to hear more from others

[Jim]

Ric,
I realize now I was not clear in my post. I never intended to compress the charge. I learned a long time ago to stay away from compressing 7383. My calculation was to determine the case capacity with the bullet seated to max. COL so it would feed in a Marlin.
How 'bout take a look at my calculations and see if you think I'm close.

Max. COL - 2.530
Bullet length - 1.265
Case length - 2.100
Web thickness - .182
calculated void - 1.083

[Ricochet]

Oh, I've since learned not to compress 7383 too, as I've often advised. I mention that because that's the way I did it, and to point out that even with as heavy a load as possible to pack in, not even half the charge would burn in .45-70 with a 340 grain cast bullet. A lighter load will burn even less. The heavier bullet will help, but I think it'll still be a mess.

[Jim]

Ric,
I'm gonna hijack my own thread.
Having calculated the case volume, I now have a starting point. My plan is to start at 95% density and compress it lightly with a granulated filler, namely ground coffee. I really believe I can get something out of this. I seriously doubt I'm gonna make history, but I do think I can at least get all the powder to burn. If I can get it up to a K in M/V, I'd be very happy with that.

[Ricochet]

With a heavier bullet, you might be able to get it to burn. But it won't with a 340 grainer, from my experience.

You might be wasting your coffee. 7383 makes a powerful ammonia smell.

[Idaho Sharpshooter]

Thunderbird Powder's Guru says to fill a case with it, and weigh it. Five times and average the weight. Take 85% of that for a start. He says it is great stuff for most of the British Nitro cartridges, since they are big cases and low pressure. I am going to be testing it in my 38-90wcf with a 375gr bullet next week, and in my 505 and 550 Gibbs with cast. It is for the 50 Spotter cartridge. I'll report back in a week or so if it doesn't snow all weekend.

Rich