Approach to loading for a wildcat

[haisardao]

Interested in knowing what people do when loading for a wildcat, mostly thinking necking down/up or "improving" a known cartridge, lest say a WSM or SAUM based case. How do you decide where to start powder charge? You go by case capacity? For example I'd like to load a 6 mm Saum, do you use 6.5 SAUM data, and start low. I know there are a lot of knowledgeable folks here and I'd like to read thier methods. Thanks
H

 

[L.Sherm]

First I Google the round, somebody at some point has done just about everything. Similar case capacity will work but in any case back off and work up.

 

[MagnumManiac]

When myself and 2 others decided we wanted something on the 300WSM case, we looked at case capacity first to the shoulder knowing full well we were NOT going to change it, just necking down the case first to 25 and 6.5. We had a lot of trouble finding powders we thought would work. There was no 7mm or 270 versions at that time. We started with powders like H4831, RE22 and 7828 that I had left knowing full well when it was gone there wasn't anymore to be had, but it gave us good data over the pressure trace.
All the powders tested, except 7828, were poor performers, so we stepped it up to RE25 firstly, then Supreme 780, the only true slow powders available to us then, later H1000 and RETUMBO became available and data went up again.
Initial data was taken from 300WSM loads reduced by 10%, but we had hangfires, dented case shoulders and strange anomalous pressure excursions. It wasn't until Quickload came about that we could choose a powder and run it and see rough results before we fired a shot. We also played with a 338 version but it didn't even come close to the 338WM and left it alone. A 35 cal was developed by a mate of mine, he called it the 35Sambar and it got pretty good results compared to the 338 version.
So, I would recommend getting QL and running your ideas through it to see what sort of results, good or bad, before delving into designing your brass. It helped me hugely to develop my 338-416 Rigby Improved 45° and 375-416 Rigby Improved 40° cases.

Cheers.

 

[MagnumManiac]

You go by case capacity? For example I'd like to load a 6 mm Saum, do you use 6.5 SAUM data, and start low

This is what I did, it did not work very well due to having nothing to compare it too case capacity wise.
You now have people already doing this wildcat.

Cheers.

 

[haisardao]

When myself and 2 others decided we wanted something on the 300WSM case, we looked at case capacity first to the shoulder knowing full well we were NOT going to change it, just necking down the case first to 25 and 6.5. We had a lot of trouble finding powders we thought would work. There was no 7mm or 270 versions at that time. We started with powders like H4831, RE22 and 7828 that I had left knowing full well when it was gone there wasn't anymore to be had, but it gave us good data over the pressure trace.
All the powders tested, except 7828, were poor performers, so we stepped it up to RE25 firstly, then Supreme 780, the only true slow powders available to us then, later H1000 and RETUMBO became available and data went up again.
Initial data was taken from 300WSM loads reduced by 10%, but we had hangfires, dented case shoulders and strange anomalous pressure excursions. It wasn't until Quickload came about that we could choose a powder and run it and see rough results before we fired a shot. We also played with a 338 version but it didn't even come close to the 338WM and left it alone. A 35 cal was developed by a mate of mine, he called it the 35Sambar and it got pretty good results compared to the 338 version.
So, I would recommend getting QL and running your ideas through it to see what sort of results, good or bad, before delving into designing your brass. It helped me hugely to develop my 338-416 Rigby Improved 45° and 375-416 Rigby Improved 40° cases.

Cheers.

This is what I did, it did not work very well due to having nothing to compare it too case capacity wise.
You now have people already doing this wildcat.

Cheers.

Thanks, that's very useful. I'm just trying to understand the thought behind creating a wildcat and picking starting loads without blowing your limbs off.
My knowledge is not enough to design any cartridge at the moment, I'll likely stick to something already made.
I did order a reamer for the 6mm UM, SaUm Improved, from JGS and have some starting numbers from the guys at Rokslide. I use Quickload and find it very useful as well.
Thanks for your input once again, those cartridges you designed look like they would hammer game at a different Zip code

 

[MagnumManiac]

Thanks, actually designed those 2 cartridges for ELR competitive shooting, although I have hunted with the 338 version quite a bit, but it's not a stalking rifle at almost 18lbs.
Had trouble finding a bullet that liked being fired at 3200fps muzzle velocity, Berger didn't like it, but the 300g Accubond started around 3100fps works very well, as does the 285g ABLR.

Cheers.