Thoughts for a new bullet maker...
Remy............. There IS a reason 99% if not 100% of all custom Benchrest bullet makers use J4 jackets...!
Never messed with Corbin swaged jackets... Don't know anyone whom has.
Played with some lotts of Sierra jackets but DAMN...! The jacket wall thickness varied within the same lot.....! Not to mention from lot to lot.
Talk about core seat punch madness!!!
The J4 jackets will still vary a touch from lot to lot for a given cal/jacket length. BUT just a few .000X ... Mr Stecker and Berger work HARD to keep the tolerance CLOSE as possiable.
Remy... Hope you have a good mentor within reach or at least within telephone reach...
Just keeping up with core seat punches (>>correct core seat punches to jacket length/bullet weight/jacket lot<<) just about damn near requires an in house tool lathe... Or at least a full set of core seat punches with half thousand steps made for you. Expect $50 -70 per punch due to difficuties of machine this steel to .0003 - .0005 ... Lotta work there.
Say about 8 -10 punches for .790 6mm jackets (60-65gr bullets) and 8-10 punches for .825 6mm jackets (65-70gr)... At least this many punches!
Now one can do one thing..... If only a limited # of punches for one jacket length/bullet weight... One can taylor the lead line (weight of bullet) so that the core seat punch / core seat die / jacket "meet up".
While making up lead cores (core swage/squirt). Make up three to five diff weights 1/2 to 1 gr increments and use these to "find" the "meet up" of existing core seat punch to particular jacket lott jacket thickness.
FYI.. There is a slight taper in the jacket from heal to mouth.
By "meet up", I mean that the lead once swaged in the jacket is fully formed to the jacket and the jacket is fully formed to the core seat die. An absolute min lead bleed by and NO core seat punch scrape on the interior of the jacket. Too small of core seat punch (just a few .0001) results too much lead bleed-by and a not so stable bullet, not to mention the jacket will want to stick on the punch...! Conversly, too big of core seat punch at the desired weight/lead line point and scrape the jacket and stick the jacket to the punch.... Resulting in poor quality bullets for sure.. If ya can get them off the core seat punch....
You may want to make a 66gr bullet.... But with limited core seat punches, you'll have to settle for a weight of bullet "63.5gr through 67.5gr weight range"... A final bullet weight somewhere in between.
Getting the lube right is a hole nother part of the equation...
Stick with J4 and good luck,
cale
