I'm reloading some Nambu 8mm necked cases using CH4D dies and 100gr FMJ bullets. I've belled the neck mouth enough to accept the bullet, but when I seat the bullet, it partially collapses the neck on one side to the point where the loaded cartridge won't fully chamber. What is the trick with reloading thin necked pistol cartridges like the Nambu 8mm and .30 Mauser?
See gun... like gun.... buy gun... shoot gun... put in safe. Repeat as necessary.
Can you post a pic of your belled case?
Should look like this. Left, sized case. Center, belled. Right, bullet sitting on belled case.
If you need help posting pics, look in FAQ's for instructions.
Seat and crimp in separate operations.
That's exactly what my FMJ bullets look like. I've not had issues with any straight walled pistol ammo I've reloaded (like you've pictured), but these little necked Nambu 8mm cases are very thin and when I seat the bullet, it partially collapses the neck.
I'm not crimping (and this seating die doesn't appear to have a taper crimp feature.. I'll try raising the die body so that the case isn't fully seated in the die.
I have has to lube the inside of the case mouth on a few similar calibers before. It might be worth a shot of you apply a light crimp afterwards.
I have also found that the brand of brass makes a big difference, but you don't have many options in 8mm Nambu beyond forming from 6.8 SPC.
Your die is adjusted too far down and is contacting the shell case before the seater plug seats the bullet to the correct depth. Raise your die a little and reset the seating depth.
What is the measured diameter of your bullets and the inside case neck diameter?
On my little bottleneck cases (25-20 and 30Mauser), I use a Lyman M die to expand the necks for cast boolits, and seating is done before crimping. In this manner mangled brass is a thing of the past.
This is my thought also.
Thanks guys... I raised the seating die a bit (and also confirmed with CH4D that this 8mm die does have a crimp feature). When I raised the seating die, the collapsed neck problems were eliminated.
What brass are you using? I am workng on a friends Nambu and am trying to source either loaded ammo or brass cases. In my Nambu thread in gd, a poster mentioned forming 357 sig brass.