Originally Posted by circa1885
A few years ago I had a custom rifle made in .35 Whelan Improved, one of several Improved versions. Within a few years a factory version of rifle and and ammo were available. I wonder if anyone knows whether I can use .35 Whelan ammo in a .35 W Imp chamber. Like everyone else I fireformed 30-06 brass to create my original .35 Whelan ammo so I thought it should be safe. Any thoughts?
The big trick to fireforming an Improved version of a cartridge is knowing for sure how the chamber was cut.
As JLA's posts states, an Improved version is usually a sharper shoulder and less tapered version of the parent.
MOST improved cartridges (like the Ackleys), if the chamber was cut properly, will support the parent case just fine for fireforming.
If the "improved" chamber was cut to deep, you'll have excessive headspace and will fight with splitting cases and possible high pressures when fireforming (even with mild fireforming loads).
Unless you know the actual version of the improved cartridge (and even if you do), the safest route is to do a chamber cast of your rifle and do some measuring with a micrometer or caliper to determine if it will support the parent case properly for fireforming.
Once you've got the brass formed, then it's time to work on the load development. LD's short description of the old velocity curve method is a pretty good method if you've got no pressure equipment to use. In addition to this process, watch the usual high pressure indicators like flattened primers, excessive head expansion, etc...
For starting loads, start with loads for the parent case and proceed from there.
Ackley's primary purpose/theory behind his improved cartridges wasn't
to get more fps from a cartridge but rather to improve case life (and accuracy) with a straighter, sharper-shouldered case.
So, after all that...long story short...
Yes, you can use your already formed .35 Whelen brass for your new improved brass.