Developing loads for unlisted powders

[MooseChaos]

I'm a long time reloader - 50 plus years - but I've always gone by developed loads with no variance. Now I have several pounds of Hybrid100V, boxes of 150, 170, 175, and even some 139 grain psp/pspbt/semi-spitzer bullets and a pristine 1941 custom 8x57 Mauser that I built... and no data to use loading.

Thoughts? I see the burn rate is between H4350 & H4831 butno data for those either? Is the case too small forthe caliber or... I use this powder in 7x57's with good success.

 

[GLTaylor]

Welcome to the world of wildcatters! We face the same dilemma on a routine basis.
If you know someone with Quickload maybe they can help you. I don't have it. Your best path is to determine what the case volume is. Then look for equivalent cartridge sizes with the bullet wt you're going to try. From there make an educated guess and be conservative. Especially so if using military surplus or old actions. Many were made to weaker operating pressures. Your pucker factor will be high when you pull the trigger the first time!
Work loads up gradually and watch for any signs of pressure. Once you find pressure you'll learn where to go in powder burn rates. Stay well away from your lands with bullet seating - say 20 thou.
Good luck and have fun learning!

 

[longestrange]

misread UR post

 

[MooseChaos]

Welcome to the world of wildcatters! We face the same dilemma on a routine basis.
If you know someone with Quickload maybe they can help you. I don't have it. Your best path is to determine what the case volume is. Then look for equivalent cartridge sizes with the bullet wt you're going to try. From there make an educated guess and be conservative. Especially so if using military surplus or old actions. Many were made to weaker operating pressures. Your pucker factor will be high when you pull the trigger the first time!
Work loads up gradually and watch for any signs of pressure. Once you find pressure you'll learn where to go in powder burn rates. Stay well away from your lands with bullet seating - say 20 thou.
Good luck and have fun learning!

 

[MooseChaos]

With this powder I'm more concerned with undercharge than overcharging. With 4895 I've gone as low as 70% of full blown with no ill effects but H100v is unknown to me as far as reduced charges are concerned. I'm thinking about going with a load equivalent to what I'd use as a starter in my 7x57 then step up as possible. Alternative is using the 7.65x53 load data for 4350 & 4831 - averaging them and reduce by maybe 5% for a starter. I found it interesting that the Argentine round that has less capacity and can be used in the much weaker M91 action as well as the 1909 M98, yet still has slow powders recommended. Looking at them I think I can safely start at @46 grains/lr primer/150 Hornady sp and work up. The 8mm has more base to push against so equivalent pressures should be lower, H100v is slower than 4350, and the action is as strong or stronger than the Argentines.

Thoughts???