Swiss GP90 mold.

[jordanka16]

Tomorrow I am picking up an 1889 Schmidt Rubin. The original ammo used a unique heeled paper patched bullet of something like .321 diameter. I found references to a group buy from NOE for a replica of this bullet but couldn't find anything on their web site. Is anyone aware of something like this existing? I suppose if I could find measurements one of the custom mold makers could probably make a one off.

Anyone else have one and have another bullet that works well?

 

[Ian]

Wow, you jumped right off into it, didn't you? I barely know anything about the K31/gp 11 ammo but had to look up the gp 90. Apparently it was not only heeled and paper-patched but hollow-based and steel-nosed as well.

If I had to start from scratch on this I'd get some 7.5x55 brass and make an impact impression of the whole chamber and throat to see what I was working with as far as loaded case neck diameter, space to fill with bullet in front of the case mouth, and all the other particulars and see if a conventional gas-checked bullet would work. I'd try that before trimming back the cases to 53mm, having a custom hollow-base, heeled, nose-pour mould made, and trying to paper-patch the odd, heeled things.

 

[jordanka16]

I tend to jump into things maybe too much with new guns, I like to experience everything about them and I tend to like old guns and that often means weird ammo. I will at least dispense with the hollow base and steel nose. The hollow base would probably require a swaged bullet, and the nose is probably just for effect on target.

I plan to make a cerrosafe cast of the chamber as soon as it arrives to see what I'm working with. Most of these rifles have normal .308-.310 groove diameters, but they have very wide tapering throats to handle the large bullet. They do alright with normal cast bullets or .308 jacketed bullets which is what the swiss did themselves in 1923. Some people have even loaded cast 8mm bullets in them with the gas check shank serving as the heel.

I do plan to just load up some regular jacketed bullets and maybe some normal cast bullets, although I would have to buy another mold for that as I don't have a .30 mold.

 

[CZ93X62]

You have caught my Obsolete & Weird Caliber Virus. It is incurable. Don't be like me, and mess around with 7.62 x 38R and 7.65 MAS pistol. Things like that are a sure road to insanity.

 

[Spindrift]

CBE bullet moulds in Australia have moulds for some unusual cartridges, might beworth a look?

 

[RBHarter]

The function of the HB is to fill up slop ....... Just saying .
Seems like based on general description that a paper patched fat 31 might be the ticket .
I patched a 7.62 once that was .305×.316 and would chamber a slip fit .323 in a fired case .

 

[fiver]

IIRC these were actually more like a 53 mm case and not a 55 mm case.
the Swiss incrementally crept forward over a succession of years from 53 to 54 then finally to 55.
they Did send most all of their rifles in and Did re-do the chambers to the slightly longer case.
but I don't know if the actual 98's got the treatment or not the 98/11's did.

anyway one thing your gonna have to watch for is die selection.
some of the older rifles and LEE dies do not work well together.
I have seen the 7.5 and the 7.65 argie both be ones where the LEE would work in one rifle but not the other two rifles sitting next to it.

 

[jordanka16]

CBE doesnt seem to have anything unfortunately, lots of cool British blackpowder rifle molds though.

The hollow base is just to tuck the paper patch into is what I read, it's in the heeled portion so it couldn't do much to take up slop anyway. Seating a bullet much bigger than .311 probably wouldn't chamber. Anyway wont know for sure until I can get some actual chamber dimensions.

Hopefully I have time to make a chamber cast today and see, I'm waiting at the vet right now with a limping dog or I would have picked up the rifle already.

 

[Joshua]

Have fun with your new project. It sounds like lots of fun.

I also have an opinion about:
Foreign military chambers VS American die makers

I’m in agreement with Fiver.
.

anyway one thing your gonna have to watch for is die selection.
some of the older rifles and LEE dies do not work well together.
I have seen the 7.5 and the 7.65 argie both be ones where the LEE would work in one rifle but not the other two rifles sitting next to it.

I load for two Arisakas, both made at the same arsenal, but years apart. The fired brass from these two rifles is very similar, not a perfect match, but very similar. The angle of the shoulders on fire formed cases from both rifles looks nothing like brass converted using a RCBS FL sizing die, or Norma and Hornady factory brass for that matter. A fired case’s shoulder looks much more life the shoulder of an Ackley Impoved case.

Headspace is another issue. with the bolt disassembled (these are cock on close rifles) I can put four layers of blue masking tape on a factory Norma or a freshly converted case (RCBS die). Three layers no smash, four layers light smash, measuring the smashed tape(super precise method) I get .014” headspace. So the dies are making the cases too short at the shoulder.

So my new method of forming and sizing involves a .012” shim when setting up my dies. I have to live with the shoulder angle, and shortened brass life that comes with overworking the brass in the shoulders.

I’m not gonna talk about the “Bulge”, just above the web.

Have fun,
Josh

 

[jordanka16]

I'll have to read and see which dies might work best. I will probably pick up a set of lee collet dies to start, they are cheap and should let me at least get some ammo loaded. Luckily the brass isnt rare or expensive, I load 25 remington for a model 8 and it's really hard on brass, brass that costs $1 per case for new or else I have to form also rare 30 rem brass.

 

[CZ93X62]

25 Remington. Viral. Toldya.

25/20 and 32/20 rifles and revolvers have poetic chambers and shoulder positioning as well. Ah, adventure travel.......

 

[jordanka16]

Finally picked it up and was able to make a chamber cast, rifle is in beautiful shape for being made in 1891, all matching and even has a bunch of stock cartouches. The bore is like a mirror.

Chamber cast:

Neck- .353
Throat- .337
Groove- .308-.309 roughly, I don't have the tool to measure 3 groove rifling properly.
Rifling starts about .83 in front of the case, so that's a long journey.

I think what I will do to start is order some PPU brass, measure the neck thickness and see what I can get away with in terms of bullet diameter and then find an appropriately sized mold with deep lube grooves? I don't know how much a grease groove bullet can be swaged without affecting its accuracy or causing leading.

https://imgur.com/a/wgOkfSS

 

[jordanka16]

25 Remington. Viral. Toldya.

25/20 and 32/20 rifles and revolvers have poetic chambers and shoulder positioning as well. Ah, adventure travel.......

Sometimes I cant help it, people sell these guns cheap because they literally cant shoot them, and i love breathing life back into them.

 

[Bill]

For light and intermediate loadings, a guy at our milsurp matches uses a double shouldered fire formed 30-06 case (a little small at the base) along with std 30 cal bullets, I have some made up but haven't shot them yet. I have shot std bullets loaded very long to bypass that very large throat with so-so accuracy, I have also squirted some paper patched at .323 through that 308 bore with moderate charges of 4759 with OK groups, I have a bunch of milsurps and this one gets shot the least

Bill

 

[Ian]

The hollow base is just to tuck the paper patch into is what I read, it's in the heeled portion so it couldn't do much to take up slop anyway.

These were 2,000 fps 7.5mm cartridges. 35K psi at least. Single-base powder is going to build pressure rapidly, so the bullet base was probably seeing at least half peak pressure while still in the throat. I'm pretty certain that the hollow lead base would be blasted out to the full confines of the chamber throat the instant it passed the case mouth and as a dynamic obturation skirt (think of the obturation cups on the bottom of plastic shotshell wads) to keep the seal all the way through the rifle. IOW much more than a convenient place to tuck the paper.

After seeing the chamber cast, it looks like .328-ish is about as large a bullet as will fit in the case neck if brass is typical thickness at the neck. That leaves an incredible amount of space around the bullet for gas to rush by and cause leading. I'd be looking to duplicate the patched, heeled, hollow base design or possibly powder-coating a heeled 8mm bullet having a .30-caliber gas check shank and check and some really deep/frequent lube grooves like a Loverin design. Squishing a bullet down .020" isn't particularly dangerous if approached cautiously, but isn't the best situation, either.

 

[jordanka16]

These were 2,000 fps 7.5mm cartridges. 35K psi at least. Single-base powder is going to build pressure rapidly, so the bullet base was probably seeing at least half peak pressure while still in the throat. I'm pretty certain that the hollow lead base would be blasted out to the full confines of the chamber throat the instant it passed the case mouth and as a dynamic obturation skirt (think of the obturation cups on the bottom of plastic shotshell wads) to keep the seal all the way through the rifle. IOW much more than a convenient place to tuck the paper.

After seeing the chamber cast, it looks like .328-ish is about as large a bullet as will fit in the case neck if brass is typical thickness at the neck. That leaves an incredible amount of space around the bullet for gas to rush by and cause leading. I'd be looking to duplicate the patched, heeled, hollow base design or possibly powder-coating a heeled 8mm bullet having a .30-caliber gas check shank and check and some really deep/frequent lube grooves like a Loverin design. Squishing a bullet down .020" isn't particularly dangerous if approached cautiously, but isn't the best situation, either.

It certainly could do that too, at any rate it can only help so I might as well have a mold made with that feature. I suspect it will be hard to find someone who can make a mold like that, any ideas?

I did manage to find some dimensions for the projectile, I was wondering if I was going to have to source a cartridge and take it apart and measure myself.

OD of bullet .317
OD of heel .302
length of heel .232
OAL of bullet 1.166

I do think I will omit the steel nose cap, since I doubt that has any effect on how it shoots, probably just to increase penetration.

Paper adds .006 to the diameters, 2 wraps of .0015 each, which is thin paper.

 

[fiver]

you also have the option of using the nose to fill across that gap and ignore it from there.
this is what the ranch dog molds designed for the marlin rifles do.

after working one Marlin over from front to back and then contacting Michael when he was just getting his designs going.
I talked to him about my impressions of the whole thing, and he had come to the same basic conclusions.
I didn't use one of his molds to solve my problem, but I did pretty much use the same solution, and got the same results.

 

[Ian]

Yup, but the Marlin only had about a quarter inch of empty cavern to span (mine did, anyway) but this is like nearly an inch. Maybe a reaalllllllly long, torpedo-shaped bullet, about .315" diameter, to stretch across the gap and make the nose plug the bore against gas escape right from the beginning.

Another solution that may not involve a HB bullet mould could involve compacting shot buffer, but man that shoulder angle....

 

[jordanka16]

I certainly plan to try other solutions, especially for more informal shooting, but I know myself, and I wont be satisfied until I can get as close as possible to the original ammo. I think a nose pour hollow base would work the best, but I'm willing to try a flat base, especially if it would lower the costs.

Any recommendations on a mold maker to use for either of those?

 

[fiver]

I know that Tom has a tapered Loverign design with gas check that makes 314 easy enough and weighs in at about 220grs.
I have one on hand.
I haven't messed with it much cause the 314299 I got jumps the gap and shoots just fine in the Argie's.