Ever since acquiring a FN 03 pistol and subsequently buying another I've done a bit of research and experimenting to come up with several reloading die combinations.
First, if you are going to reload the 9mm Browning Long, you will have to choose a bullet size/diameter that you want to use. For jacketed bullets, the cartridge is designed to shoot a 359 bullet, some sources even say a 360 is best, and you have the option of going 355 or even 356. Ideal diameter for cast depends on the groove diameter of your barrel.
Probably the only current available factory ammunition is produced by Prvi in Serbia, and it is loaded with a 108 grain bullet at an advertised 1150 fps. I therefore selected a 110 grain 357 bullet, either a Hornady or a Winchester, to match factory ammunition.
To re-size the case I found that a 38 special carbide die sufficiently sizes a fired Prvi case.
For a trimmed 38 Super case, which has slightly thicker walls, a sizer for the 38 Super would probably work better, as my 38 spl die sizes the case a bit too much, a seated bullet creates a visible bulge in the neck, which is larger than the body.
The Prvi case weighs just under 51 grains and a trimmed 38 Super +P weighs just under 58 grains. There is about a 3 to 4 thou difference in wall thickness at the case mouth. A m/07 military round specifies a 54 grain case. The Prvi case probably has a case wall thinner than military ammunition and a trimmed 38 Super probably has thicker walls, I don't have a sample military round to measure, so I did some assuming. Varying case thickness occurs with other calibers as well, varying from brand to brand, and is not usually an issue. Bottom line being, the sizing die has to reduce the neck diameter enough to ensure a snug bullet grip.
For expanding the neck, I use a 38 S&W LEE powder through expander, made to expand for 357 dia bullets. A 9mm Luger die will work for 355 of 356 bullets. Pistol die sets vary brand to brand, some decap with the sizer, some decap and expand, so if you are searching though your collection, try a set that has a similar case length.
The bullet seating and crimp die selection is fairly open, my 9mm Luger die has a seating plug that matches the bullets I'm using and does a nice taper crimp.
If you don't have any 9mm/38/357 pistol dies in your collection, caliber specific dies are available from Redding and also RCBS, but they are a bit pricey, I haven't used them.
I bought and use a 38 Short/Long Colt die set from LEE. The LEE set is a 3 die set, the sizing die decaps and it is marked 38/357-H3, the powder through expander is marked 38 S&W-G3, and the seating crimp die is marked 38 AUTO-C3. Because the plug for the LEE die is for a RN bullet it deforms the soft lead nose of the Winchester JHP # WB38JHP110 bullet that I am using, so I just substituted a 9mm Luger die, from RCBS. Crimp quality is the same with either die.
A 9mm Luger die will do an excellent job of neck sizing a fired case, leaving only a small portion of the lower body un-sized.
Load data is another issue entirely, and although I have tried a few different powders I'm a long way from having data that I can share.
