1 1,000'th of a mm

[stx kid]

IIRC, Prvi brass runs hard. Probably why it won't size right.

hence why I ordered a crimper die to try remedy this problem.

 

[ROGER4314]

The Jap uses the same diameter bullet as the .303 British. As I recall, it's about .311"-.312". If you're using .308" bullets, they'll drop right through the neck.

Flash

 

[stx kid]

The Jap uses the same diameter bullet as the .303 British. As I recall, it's about .311"-.312". If you're using .308" bullets, they'll drop right through the neck.

Flash

I have two boxes of .312 soft point from hornady. i don't think that this is the issue

 

[M. Sage]

The good news is that the Arisaka stole controlled feed from Mauser (the Arisaka is every rifle... literally), so you shouldn't need a really good crimp.

 

[stx kid]

I'm not all that interested in having a factory crimp, i just want to be able to keep my bullets from slipping out.

 

[Paul5388]

You can set the FCD to use the bullet as a mandrel and get more neck tension. Of course, that still ask why the neck is too big to start with. I would be looking at the expander ball and ensuring it isn't too big.

 

[Dawico]

You need neck tension and a solid crimp won't fix that. Mic the expander ball and see what it says.

 

[Dawico]

You can put the expander in a drill and use some fine grit sand paper to knock it down a little. I honestly don't know what it should measure but it being too big or small are both problems. Go easy and check it frequently. The bullet should be very tight when you seat it.

 

[stx kid]

You need neck tension and a solid crimp won't fix that. Mic the expander ball and see what it says.

its at .311.... i think that this is just crappy brass then....

 

[Dawico]

I will check some of my dies shortly and see what they measure.

Very hard brass may not shrink back down after the expander ball passes by. Makes sense but I have reloaded about every brand of brass made and haven't had that issue ever.

 

[stx kid]

So if its just a matter of the brass being hard then should I aneal it?

 

[Dawico]

I haven't gone in to check any dies yet, but a quick search shows that your expander ball should measure .003/.004 under your bullet size. This makes sense to me.

I would either contact the manufacturer and have them replace your expander ball or use the above methods and size it down (my choice, I don't like to wait).

I don't think the brass is the issue.

 

[Dawico]

Alright, after measuring here is what I found. My .308 expander ball measures .305. My 8mm Mauser (.323 bullets) measures .319.

Your expander ball is too big.

 

[stx kid]

Roger that.. Now all I need to do is wait for some more brass

 

[Paul5388]

Good job Dawico! I think you've found the problem.

 

[M. Sage]

I will check some of my dies shortly and see what they measure.

Very hard brass may not shrink back down after the expander ball passes by. Makes sense but I have reloaded about every brand of brass made and haven't had that issue ever.

I'm thinking the brass is hard enough that it's staying expanded from firing.

A lot of guys will anneal Prvi brass to soften it for reloading.

 

[robocop10mm]

I will second the anealing idea. Brass work hardens. The necks should allow the expander ball to be drawn out and spring back a little. Hardened brass will lose its springiness. I aneal every bottleneck case EVERY time. Brass has gotten precious, Anealing extends the life.