91 Mauser chambering problem

You're sure that you don't have Belgian (vice Argentine) Mauser dies? I can't think of any reason that different headstamp brass should put you that far out of spec so as to be completely out of headspace-forming range.

I don't know the answer to that. My Arg dies are Lyman. I always assumed that all the 7.65s would be the same. What reason would Mauser have to alter things
and make their supplying of ammo problematic ? They supplied Belgium, Turkey Spain and many South American countries with at least their initial ammo supply.
As for Remington brass, I do know that many people don't like it too much, for various reasons. I choose Winchester when there's a choice.

You can correct similar sizing problems by running the brass though the zier then rectracting enough to spin it 180° and resize again very slowly.
This type of problem is influenced by the amount of lube on the brass, how fast you size it, the temper of the brass and the size of the previous chamber the brass was fired in.

There's one more indication that the problem is press flex and a need to screw the sizer down a bit more to compensate. Different makes (and lots) of brass have different mass and temper. It appears your Remington cases are somewhat more resistant to sizing than your LC. As a result, the press and sizer are probably flexing more with the stiffer cases and not receiving the same degree of reduction in head/shoulder length.

Before you decide to scrap those cases, try sizing them again after screwing the die down about 1/8 turn (.009") beyond where you had it set before. Then see how they chamber. You might be pleasantly surprised.

There is no sense in tossing any brass. Just size it until it works.

I will comments that the 7.65 Mauser has the most messed up set of sizing die standards on the market.
I have 4 brands of dies for the caliber and only one sizer the RCBS is correct.
I ran into a rusty orphan RCBS sizer at a guns show and it too is correct.
Most of the other dies give grossly excessive headspace in the rifles that I own.

I checked my handloaded ammo, Norma factory and Prvi Partizan against a L E Wilson case gauge and they all agree with the case gauge.
None of the cases sized in the non-RCBS sizer dies matched up to the Wilson gauge.

Maybe I should start a collection of case defects.
I have some cases of almost every brand that have horrible birth defects.
I have one case that has a big fault line running down the inside that is not visible on the outside. It is only noticeable because it is a straight wall rifle case that you can see into.

Well, tomorrow is my shooting day {Wed] so when I'm done I'll have 50 or so cases to experiment with. I'll try a little more cam on the die, turning 180 etc.
However, if ireload is correct about the dies all being out of whack except the RCBS - well, we'll see. I'll probably end up just neck sizing + my 311 M die.
I've noticed one thing - extra hard bolt closing does not help accuracy.
I'll be back

Turning the die 180 degrees (1/2 turn) would probably be way too much. With the 14 TPI thread, that much rotation would lower the die 1"/14/2=.036" - far more than typical press flex. Somewhere around 1/8 to 1/4 (.009"-.017") turn beyond no-load contact is usually enough.

Forget about the "cam over" advice. It's much too subjective and doesn't apply to all press designs (some stop at TDC with no "camming" action). Just be sure to look where the die meets the shellholder. If there's a gap, you aren't using the sizer fully. Holding white paper on the far side can help visibility.

https://www.milsurps.com/images/impo...espring2-1.jpg

I think Ireland2 meant turn the case (not the die) a 1/2-turn and run it up again for a repeat sizing step. That might help just from the double-tap invoked.

I would, however, use the calipers/.38 case measurement technique shown by Matt in an earlier post, to check the *relative* headspace of your resized cases. I just tried it out tonight w/ a half-dozen fired 30-06 cases as compared to an RCBS Precision Mic and the (relative) results were dead-on within a thousandth.

As I said before, "neat idea."

>>>use the calipers/.38 case measurement technique shown by Matt in an earlier post,<<<
It is an excellent idea especially since it can be a free tool.
I use the Stoney point tool that works the same way but I had to pay for mine.
The 9mm case should be excellent especially when comparing a sized case to a well fomed case fired in the same rifle.