Imr 7383, 458 wm, 375 h&h?

[Tatume]

Hello Folks,

Lately I've been shooting a lot of 350 and 400 gr cast boolits in a 45-70 High Wall using a compressed load of IMR 7383. Although it leaves a lot of unburned powder behind, I'm getting 1350 to 1400 fps with good accuracy.

Now I'd like to try this powder with the 458 Win Mag and 375 Holland and Holland, both cartridges in Ruger #1 rifles. Have any of you tried IMR 7383 in these applications?

Thanks, Tom

[Jim]

Tom,
I have used 7383 for years, but I must admit I have not used it in .375 H&H or .458 Win Mag.

I have, however, fired loaded rounds in a .458 that were loaded by a friend. I gave him a pound for him to try out.

At the risk of being over cautious(is there such a condition?), I will tell you that this stuff is very finicky. At some precise point above 100 % CD, the pressure curve goes up like a bottle rocket. I ruined a reproduction Sharps rifle in .45-70 with this powder by not paying attention.

When working up loads with this powder, it is my practice, once the load reaches 100 % CD, to proceed by ONE GRAIN increments, watching closely for pressure signs. Believe you me, they WILL show up.

Most of the guys here that are very familiar with this powder have discovered the telltale sign: Given that the primers are not riveted and falling out of the pockets, when all the powder burns, that's the limit.

The largest caliber I've worked with using this powder is .45-70. I have loaded LIGHTLY compressed charges under 500 grain cast boolits with it and made it work.

Proceed with caution and keen observation. WATCH THE PRIMERS. They will tell you when they are hurting. All powder burnt or not, when the primers start to flatten and begin to rivet, it's time to stop. If you have remaining rounds of heavier charges left to fire, take them home and pull them down.

Trust me, it ain't worth taking the risk of firing that one last set. That might be the last one you fire.

If you make this work, I'd be really interested in hearing from you about your results.

[Nobade]

Not an H&H, but I have been shooting a lot of 7383 out of my 375 Taylor. (338 win mag necked up, slightly less capacity than an H&H) I haven't tried it with J-bullets, but with paper patched cast bullets I haven't been able to overload it. Normally I just fill the case to the base of the seated bullet, and that is a very mild load. I also have tried drop tubing the powder in, and it makes a more energetic load but still quite mild pressure wise. It'll get a 265gr. bullet up to 2350 fps from a 23 inch barrel. I do not use magnum primers with this powder. I have seen pressure problems in my 300 win mag using mag primers, never with normal ones.

[Tatume]

Hello Folks,

My letter to Hodgdon:

Please be so kind as to tell me whatever you can about IMR 7383. I'm loading this powder in several cartridges, using the Ken Waters method to judge pressure. As near as I can tell it appears to be close to IMR 4064. Any charge data you can share, especially in 375 H&H (Ruger #1), 458 Win Mag (Ruger #1), and 45-70 Govt. (Miroku Winchester High Wall), would be greatly appreciated.

Reply from Hodgdon:

IMR7383 is a military product that was never intended for civilian distribution. No data have ever been developed for commercial cartridges with this powder by the IMR company. It comes in a wide variety of burn speeds as is common with military powders. It is getting very old now and should be constantly monitored for any signs of deterioration as it may self ignite at or near the end of its lifecycle. The sole use of this powder was in a very specialized 50 cal Browning cartridge. This is all we know about the product. We would consider it too old for storage in a home or structure. I think you are way off on the burn speed.

Forwarded to Jeff Bartlett, reply from Jeff:

Hodgdon's warning is applicable to all powders. The danger of spontaneous combustion is always present, depending on the storage environment the powder has been through. Powder deterioration is accelerated when it has gone through extreme temperature fluctuations during it storage life. This IMR7383 was bought directly from the military, having been stored in proper propellant igloos. After purchase, the powder was stored in underground propellant bunkers. I have no worries about this powder.
By the way, this powder is much slower than IMR4064. It is similar to IMR4831, but when loading to equal volumes.

Take care, Tom

[Maven]

Tatume, If you own or can borrow a chronograph, load development with 7383 will be much easier. My expererience with it in the .243Win., .30-06, and 8 x 57mm, essentially corroborates what Jeff Bartlett said. However, since we really don't know how fast or slow YOUR lot is, here's what I'd do. Use a good reloading manual to determine starting loads with a given bullet weight with IMR 4064 or H 380. Chronograph them and compare to the velocity in the manual. I'm guessing they'll be too slow. If so, use starting loads for IMR 4350 and chronograph them. If they're still too slow, go to the next slower powder and repeat the process. Be alert for pressure signs with 7383 as they occur without warning. I.e., sometimes the addition of 1 gr. to a load is enough to create unacceptably high pressure. Moreover, you don't want to heavily compress it either...for the same reason. Lastly, I got excellent performance with it using jacketed bullets in the aforementioned cartridges using IMR 4350 [starting] data. It works OK with CB's in the 7.5 x 55- and 8 x 57mm cartridges as well.