Forster is who Mr. Guffey called to get the operating details from, so he is aware of Forster's name.
My own experience with the bump concept is very limited. I read about it in Precision Shooting in the '90s where there were a couple of advertisers selling die blanks. IIRC, the rifle builder was to drill and ream the blank to create a body die using the same reamer he chambered the rifle with, and then send it back to the vendor to be put through gas nitriding to harden the surface. I don't recall if that service included polishing. The die reaming would be done to a length that would bring shoulders back about -0.001". The neck would, of course, have to be sized separately. This way the die would support the case while the shoulder was extruded back, but not narrow it any further.
That kind of die would be married to the barrel and any others chambered with that same reamer to the exact same chamber length until the reamer dulled enough to be making the chambers smaller. If I am correct that I have described a bump die true to the original concept, then no mass-produced die can get there accurately. I'd have to speak to Forster myself, but I suspect their version, from Mr. Guffey's description, just adds a neck sizing bushing to a body sizing die that just doesn't resize as much as a standard FL die does. Maybe it's made to match SAAMI minimum chamber diameters. But I am just speculating here, as I haven't spoken with them about it myself.
The headspace terminology debate got twisted to motive and character assertions that are unfounded and violate Rule 3. of the forum rules. I will go ahead with the headspace post because not all is as it appears. Despite claims I am one of only two terminology-Nazi's on the board (and if you think there are only two candidates for that title, watch how quickly any number of members jump to correct a newbie who refers to a detachable magazine as a "clip"), examination of my past posts will reveal that I did, myself, use Case Headspace and Cartridge Headspace at one time, defending their legitimacy based on the same assertion by others that everyone knew what I meant by it. But I gradually ceased to be sanguine about that. Here's
a recent article illustrating why. It defines Cartridge Headspace as a synonym for Chamber Headspace, as in, the headspace the cartridge fits into. I don't know that we'll actually see a newbie mistakenly buy a headspace gauge instead of a case gauge because of term confusion, as I suggested earlier, but stranger things have happened. Anyway, I am as tired of this boorish thread hijack as everyone else, and want to move the contributions on the matter elsewhere, so I'll get the thread up.
Maybe instead of a headspace sticky I should just put something up called Terminology Rumble and everyone can get it all out of their systems there.
Rox,
You are correct that it takes very little turning to get a die adjustment in thousandths. The reason press instructions recommend an added fraction of a turn is to compress the shell holder against the die harder than is strictly necessary. It makes the instructions simple and it ensures a person sizing mixed cases won't have a reluctant one open a gap between the die and shell holder. Redding's Competition Shell Holder sets are made to allow that extra force to be employed even when you are not seating to true full length. But if you keep your cases segregated by lot and load history, you don't have to use it. Just setting the die to the right height works reasonably well, though a little variation still occurs.
I once suggested to Redding that they change the knurl on their lock rings from a diamond pattern to 71 or 72 straight grooves around the perimeter so the grooves could be used to count thousandths of change in die position using a reference mark. I even found the right metric knurl to make the circumference come out right at the current diameter, but, alas, no love.
Dufus,
You are correct. Mr. Guffey points to resizing being an extrusion operation the same as case forming is, but smaller in resulting change. Maybe I should add registration spots to my exaggerated resizing illustration to show the movement of brass. Resizing cannot push brass that has thinned at the expansion ring back into place because it is thicker there than it is higher up on the case wall. So the resizing die comes down and moves the top end of the case wall into the bottom end of the shoulder and the top end of the shoulder into the neck. That's how necks grow to require re-trimming. The shoulder then has lost a little of its original brass to the neck and gained some from the case walls and is no longer the exact same piece of metal.
He is also correct that firing a cartridge in too much headspace presents little or no hazard. If it did, the Ackley Improved chambers could not fireform their parent cartridges directly. I was at the range once when a fellow came up to me with a .308 case that had just a slight rounding where the shoulder and neck had been, terminating in a hole where the mouth was. He had fired it in a 30-06 chamber. The bullet hit low, but otherwise, all was well. A .308's wider shoulder would not fit in a minimum 30-06 chamber if that shoulder was at SAAMI maximum dimension, but you seldom see either chambers or cases made at the minimum and maximum, so it fit. What about headspace during this event? The extractor hook kept the case from running away from the firing pin. It's not easy on the extractor hook, but they will usually do that without breaking.
As to the firing pin pushing the cases forward, it depends on the cartridge. We know cases in chambers with excess headspace do go forward before the pressure gets too high because firing thins them at the pressure ring. If the case stayed to the rear, instead of thinning at the pressure ring, the shoulder would blow forward just like fireforming an Ackley improved parent case does. There is more than enough energy in the primer to back it out to act like a little piston helping push the cartridge forward, as well as there being enough momentum in the firing pin to do that. But with military ammo, the primers are crimped and can't back out, so that mechanism is eliminated from consideration for them. Military ammo still thins at the pressure ring, even when fired in an '03, which doesn't push the case against the headspace stop with the nose of an extractor claw. Again, we know the case goes forward because military brass also stretches at the pressure ring. I don't have any sense of how much the cartridge might bounce off the end of a chamber when a semi-auto extractor claw shoves it in and then snaps over the rim. Always something new to explore, I find.
Anyway, I've said more than enough and I think others have, too, and with all the violations of rule three regarding assertions and attributions about members characters and motives, I think it's time to shut it down and let people wait for the sticky.
