Forster Coax Shell holder Adapter

Coax press put a lot of bearings on die collar. Some die manufacturers don't design the collar for such load bearing applications. The collar will come loose and the amount of shoulder bump may become inconsistent.

The best die collar is the Hornady lock-n-load. I bought a bunch of them to swap out sizing die's collar. The worst collar is Lee.

-TL

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You gain the ability to use the oversized Redding competition shell holders but lose some of the self-aligning ability of the press shell holder. A runout gauge will tell you if that has turned out to matter or not.

I generally use Forster's lock rings in the Forster press since they are sized for it. In addition to tightening its cross-bolt, you can use a Sharpie or a pencil to add a registration mark that will tell you if it has slipped at all. However, on occasion, I have used a Lee lock ring upside down to get the rubber to help float the die alignment with the case. You do need a registration mark, though. With the rubber, I've used Whiteout correction fluid in the past, but also a silver-color Sharpie.
 
Lock ring is the proper name. Thank you.

For marking, sharpie fades with use. I just "tatto" it on with electric pencil.

I never understand the necessity of match shell holder, or shimming with feeler gauge. Why not screw down the die a little? I especially don't like shimming with feeler gauge. The pressure, easily thousand pound, will squash the gauge thinner.

-TL

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The shimming and match shell holders do opposite things. The standard shell holder has a deck 1/8 inch above the surface the rim sits on, so it won't let the die mouth get any closer to the bottom of the case than that. The shim slips under the case, effectively raising the surface the case sits on, but not the deck, so the die in contact with the deck is then less than 1/8 inch from the back of its head.

The competition shell holders have taller-than 1/8-inch decks in +0.002" increments. This lets you bring the die mouth into solid contact with a selected deck height without the case entering the die as far as the standard deck would allow. The reason for doing this is many folks have found it difficult to get consistent sizing length if they simply back the sizing die out of contact with the deck. This is because cases don't have super-exact dimensions, so some resist sizing a little more than others within the same lot, and this is worse with mixed load history or mixed lots or headstamps. This causes inconsistent press stretch, so the harder-to-size cases come out a little longer from head to shoulder. The taller deck lets you screw the die in far enough to make full contact with the taller deck which puts additional pressure on the harder-to-size cases to get them into the die just as far as the less resistant cases go, while still not driving the less resistant cases too far into the die. Nothing completely eliminates case-to-case sizing variation because spring back isn't perfectly identical, but the competition holders seem to cut it in half or better.
 
Thanks for the explanation, Unclenick. Interesting points about the competition shell holders. I thought they function like shimming up the brass.

I'm still no fan of shimming. Screwing down the die is my method. Very rarely I did run into the top desk of shell holder and couldn't go far down enough. They were all fanny calibers with custom made 4CH dies. Guess 4CH machined the die body a bit too long. They offered to correct that, but I just did it myself with belt sander.

Very interesting about the competition die idea. So the press always flexes on the shell holder's top deck. It sort of regulates the sizing action. Say the press generates 1000lb force. A hard brass would take 800lb, and the shell holder takes 200lb. A soft brass takes 600lb, and the shell holder takes 400lb. So the harder brass will get its attitude adjusted more than the soft brass. Makes sense.

Perhaps it is because of the type of guns (milsurp) I usually shoot, I almost never have the die bottomed out on the shell holder. I sometimes even purposely raise the die a couple of turns higher to partial length resize.

Brass' resistance to resizing could be due to insufficient lube on the shoulder. We have been programmed not to apply lube in that area to avoid denting. But I think some lubricity is needed to facilitate the "flow" of brass. I apply lube, still sparingly, to the neck and shoulder when bumping is expected.

-TL

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Tang,

I run into this exact issue with my M1 because it is so violent on the brass, when the bolt rotates and extracts the cases it stretches them at inconsistent rates, annealing doesn’t seem to really help.

My next course of action is to shoot some cases withthe gas plug out so I will have eject manually, and measure my shoulders and see if they are more consistent.

But Honestly sometimes I wonder if I can even shoot good enough to even notice the difference .

But I do notice virgin brass seem to produce the smallest groups.
 
That's the reason the military marksmanship units always load new brass. They've tried reloading and just couldn't get their grouping as tight. That said, like people buying once-fired brass, they've got fired brass coming out of a lot of different chambers, and that is hard to overcome with conventional seating dies. I've taken Camp Perry pick-ups and run them all through the same die setup and measured as much as 0.005" difference in the head-to-shoulder length. Part of this is the fact some cases come out of some guns fatter than others, so they extrude out longer in the sizing die. Another, less obvious issue is that a lot of Garands and M14/M1As don't have their bolt faces perfectly square to the chamber because they aren't blueprinted, so cases come out with their heads slightly out of square, or else have a bent rim from hard extraction. Either one makes recoil favor one side of the bolt face during firing. Harold Vaughn was able to measure the resulting off-axis and randomly directed recoil moment which moves the muzzle along its axis, causing dispersion.

If you shoot all your cases out of the same gun, and you square the heads and get them sized to the same length, the issues are theoretically escapable. It may be that roll sizing can get around the problem, too, if the plates are sized and run true. There are other workarounds. If, for example, you have a Wilson case trimmer, the trimming cutter can square a head as well trim a case mouth. It is dreadfully slow, but if all you do is touch the head with the cutter, it will mark an uneven head so you can sort it out or, for single-loading, use it to orient the high sides of the heads all the same way in the chamber, which cuts their group-fattening influence in half.


TL,

Screw a sizing die down into light contact with the shell holder deck. Then lube a case and slip it into the shell holder and run it up into the die and use your set of feeler gauges to see how thick a gauge you can slip between the deck and die mouth. That thickness is how much the press has stretched.
 
Unclenick said:
Screw a sizing die down into light contact with the shell holder deck. Then lube a case and slip it into the shell holder and run it up into the die and use your set of feeler gauges to see how thick a gauge you can slip between the deck and die mouth. That thickness is how much the press has stretched.
Click to expand...

In order to use the competition shell holder, the shell holder slightly above the gap measured as you suggested should be used, so when resizing there will be no gap. Do I understand it correctly? Thanks.

-TL

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Nick,

I wonder if they ran the new cases thru a sizing die, or do they just size the necks only? Every new case no matter what manufacturer has always fit into a case gauge every single one of them without running it thru a sizing die

I have always wondered how they developed there load’s exactly.

I dont know if anyone else does this, but fired cases I would practice with and new cases were for scores in matches etc. was just more economical for me.

Bart B would be a great one to ask but I havent seen him on here in a couple years
 
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Will,

I don't know about pre-resizing. As you say, that's something Bart would be likely to know..


TL,

I was just describing a way to see how much your press is stretching under the force applied during resizing using a standard shell holder. Most die instructions for full length sizing have you turn the die into contact with the deck of the shell holder with the press ram all the way up, then lower the ram and turn the die in another eighth to one third turn, the smaller numbers being for cast iron and the larger for the more easily stretched aluminum presses. That's about 0.009" to 0.024", so that is about how much the manufacturers expect their press frames may be stretched by sizing force with larger cases.
 
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