Re-swaging boolits during seating?

[jschluter]

This may not be the correct forum, but here goes. I have slugged the barrel of my '74 Sharps (45-70) and decided on boolits 0.000 to 0.002" oversize. I'm also case neck sizing 0.002" under the boolit diameter. Now, how much re-swaging am I gonna do to the driving bands on soft 20:1 or 30:1 boolits as they are pushed into the interference fit of the case neck? The surface area of the driving bands is small and lead is soft compared to the brass case. I can see this as a non-issue if the front driving bands are seated outside of the case neck and create the seal while the milliseconds pass for proper obturation at the base. But, if all of the driving bands are inside the case neck and re-swaqging does occur, gas cutting could occur before the obturation seals the gas off. Or is this a case of thinking too much? I haven't seen any discussion on this topic in my visits to the forum so maybe that's my answer. But, I'd still like to see a discussion by the wizards. Thanks

[40Super]

Try to seat a couple boolits in cases and pull in a few days to measure if they swaged down. Only way to know for sure. If they are smaller, a new expander may be in order that is bigger to reduce tension. Normal tension doesn't generally swage slugs down but some cases can.

[MtGun44]

I agree, pull a few and see. I have always wondered if this might be why a lot
of serious target shooters with the BP long range sports anneal the brass every
cycle. Soft brass would prevent swaging down a soft lead boolit.


It definitely can happen, fairly common with 9mm Luger, based on our number
of threads where this winds up being a factor.

Bill

[prs]

Soft lead with frail bands will require that you take special steps to keep swaging to a minimum. Keep the boolits sized to close to groove diameter. Keep the brass necks soft. Use an internal sizer just under boolit diameter. With heavy boolits in single shot arms, consistent neck tension is more important than strong neck tension. Seating boolits out to kiss the lands can compensate for lesser retention too. Keeping the base band as perfect as possible IS important for a gas seal.

prs

[jschluter]

I took the advice from several respondees and pulled a few of my loads. Unfortunately they were Lyman #2 (BHN 15) rather than the 20:1 or 30:1 mix. The boolits started at a swaged diameter of 0.460" and finished at 0.460". No detectable difference, but there was a very distinct swell in the case neck. Thanks for ya'll responses.