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Drilling: G.F. Stormer: Initial Workup
Old 10-20-2010, 12:51 PM
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Default Drilling: G.F. Stormer: Initial Workup

Go here: http://thehunterslife.com/forums/showthread.php?t=15176 for the story on how I came to own this piece.

As I said in the above thread, I thought the chambering was 10.75 x 58 Krag Petersen. It isn't. I cast the chamber and slugged the bore, and it's longer and 'wider'. Now, I think it is one of the following.

In order of likelihood of being correct:

1) 11x60 Gras

2) 11.5x57 Spanish Reformado

3) 45-90 Winchester Center Fire

There are "problems" with each of the above. I think a table containing the dimensions of each of the above cartridges and the chamber casting will facilitate the comparisons best.

As you can see, there's something "wrong" with each of the 'candidates'. For example, the 11x60 Gras is close in head diameter, neck (mouth) diameter, and case length, but the caliber is larger than the 0.445" of the Gras and most importantly, the chamber does NOT have a shoulder AT ALL. And so on.

I measured the chamber casting every 0.125" from head to mouth, and graphed the results which yields a profile of the chamber. I don't find any cartridges in Donnely's book that match the dimensions and the shape of the chamber. Here's what the graph looks like. (I "squashed" the top image to exaggerate the taper just ahead of the head so it's easier to see.)

Basically, the taper is 0.010" per 0.125" of case length for the first ~0.625", then it's ~0.003" per 0.125" of case length to the mouth.

A .348 Win still "works" as a starting point. I 'beat' on on 'til I could get it to chamber, and then loaded it for fire-forming and formed a case. That was actually what got me off the 10.75x58 Krag Petersen immediately.

Here is a picture showing from left to right a fired .45-70 Gov't case, the abused .348 Win case after fire-forming, an 'unabused' .348 Win case, and the chamber casting.

The fire-formed case looks so bad because of the shape of the chamber with that sharper taper near the head and more gradual taper to the mouth. Looking at the chamber cast it's difficult to see those two different slopes. Since the rim and head of the .348 fit the chamber so well, and the .348 is a sharply tapered cartridge, I thought it might just 'drop in'. Au contrare. The width of the .348 Win about half way up the case is larger than the chamber. As I 'squoze' the upper body of the .348 to fit the chamber, the lower body expanded. There was a lot of grunting and groaning and the result was 'ugly', but in the end it fit the chamber and after fire-forming provided useful information.

The rifling of these old Central European combination guns are complex. (It's often similar to "Whitworth" rifling.) There are at least three and sometimes four separate diameters. This piece was advertised as a "10 mm caliber". It isn't. It is at least an 11 mm caliber, and probably an 11.15. However, how do you decide which it is when there are four diameters to choose from?

I measured the bore (in all it's various dimensions) from the chamber cast. The result suggested that it might be some sort of .45 caliber, maybe even a .458" (11.5mm-ish). I dropped a .45-70 bullet into the mouth of the fire-formed case, and it fit just as expected for a fired case - nice slip fit.

I was beginning to believe that it might be a .458" (11.5mm-ish) of some sort. Not assuming that the muzzle end of the bore had to be the same as the breech end, I took a lead bullet that was nominally .458" (.459" actually), and pressed it into the muzzle. It didn't get far. However, the measurements from that bullet engraved at the muzzle, were identical to the measurements just ahead of the throat from the chamber cast. Quality gunsmithing.

Clearly a .458"-ish bullet was not going to work. I knew this bore was larger than the Collath's, but just to make sure, I pushed one of my bullets cast for the Collath - 0.423" (10.75mm) - into the muzzle. Only the highest lands engraved the bullet. So, the 'caliber' is somewhere between .423"-ish (10.75mm) and .458"-ish (11.5mm). I'm thinking it's 11.15mm or something near .452"-ish. I have a mold for casting .45 caliber bullets (nominally .452" bult probably .453" or .454"), for my .45 Colt, but I haven't used it yet. I will get it out today and make a couple to use see how they fit.


I am going to send Hornady some drawings and a chamber cast and have them make some dies for me. Might as well get the pieces that make cases to fit the actual chamber dimensions. I don't really care if it is some "known" cartridge.

I intend to use .348 Win brass. If necessary, I will get a reamer from Dave Kiff at Pacific Tool and Die and make a "forming" die.

I will see how the bullets that the Lee .452" bullet mould throws, fit the bore. Since this is most likely a black-powder-only situation, I'll be using lead bullets anyway.

This cartridge is very similar to the .45-90 Straight. I expect the charges and ballistics to be similar as well. Of course it's also very similar to the .45 Alaskan (a .348 Win blown out to .458), but the "Alaskan" is straighter and a .458" not a .452", so I'll start with loads from the .45-90. My .452" bullet mould (452-255-RF) throws bullets that are supposed to be .452" and 210 grains. I'm going to "make" a cartridge up in QuickLoad and see what external ballistics are like.

More when there's more to report.

Then you will know the truth, and the truth will set you free. John 8:32

"We make men without chests and expect of them virtue and enterprise. We laugh at honor and are shocked to find traitors in our midst. We castrate and bid the geldings be fruitful." ~ C.S. Lewis.

Do not confuse technical skill for wisdom and do not confuse strength for skill. Paul Skvorc

Last edited by gitano; 10-20-2010 at 01:56 PM.. Reason: Typos and readability
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.439 caliber, black powder, bullet sizing, cast bullet, custom brass, custom dies, drilling, lathe, load work-up

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