Question about precision dies

[Tim K]

I'm confused by your sizing procedure. I see you sizing the case down with a body die and then expanding the neck? Obviously, the neck diameter needs to be smaller, not larger, so I think there is something in your process I don't understand.


Myself, I want to size the body and the neck in the same operation. Seems to me that should be the optimal situation for maintaining concentricity.


I've gotten away from bushing dies and have moved to Forster dies that they hone to the exact neck dimension I want. These work great and don't leave that little section of the neck unsized like a bushing. It's cheap. Like $17 IIRC.


I've noticed that the lube step is a much bigger deal than I'd originally thought. If all my cases are not lubed close to exactly the same, I get varying dimensions to the shoulder. Something to keep in mind in your process.

[DireWolf]

I'm confused by your sizing procedure. I see you sizing the case down with a body die and then expanding the neck? Obviously, the neck diameter needs to be smaller, not larger, so I think there is something in your process I don't understand.

Myself, I want to size the body and the neck in the same operation. Seems to me that should be the optimal situation for maintaining concentricity.

More likely that I'm missing something or didn't explain properly, but the idea here (based on research only at this point, haven't ordered the mandrel/die pairs yet to split this out), is that the mandrel-based expansion is able to maintain better tolerances (e.g. size & neck tension consistency) and concentricity over the expander ball in a FL sizing die.

So, unless I'm missing or misunderstanding something (easily possible), the FL die will size the case down first (below target neck diameter), then unlike having the expander re-upsize the neck (and set neck tension) in the same step, as a subsequent step the mandrel will expand the neck back up to -.002 (or -.001 if needed), and will be more consistent/concentric, in part, due to direction of force applied during neck expansion.

The expander die body is universal (e.g. doesn't downsize/compress case), so both downsizing to proper headspace (and sub neck size), as well as expanding to (optimal neck tension) target diameter both occur during the compressive part of the operation, which should support tighter tolerances on the whole...(in theory at least, still need to test).

Hopefully I'm not missing/misunderstanding any fundamental premises here...

I've noticed that the lube step is a much bigger deal than I'd originally thought. If all my cases are not lubed close to exactly the same, I get varying dimensions to the shoulder. Something to keep in mind in your process.

That's good to know, and makes perfect sense now that I'm thinking about it. Great tip, thanks!