Monthly Archives: January 2021

7.8x19mm- Closer, But No Cigar

So the finishing chamber reamer I ordered was supposed to arrive today, and with minor modification I would have been able to ream the chamber. Sadly it did not arrive, and tracking now says it will arrive Monday. I’m not a patient man, so we’ll get back to that shortly…

One thing that was needed was for the gun to be .30 caliber, which meant lining the bore. I had a short section of .308 Winchester barrel rifled 1:10. A little research showed that .30 Luger also used a 1:10 rifling pitch and shoots bullets in the same weight range as the 7.8, so I figured this would work fine. I turned the section down on the lathe, then drilled the barrel through from both the chamber and muzzle ends. the liner was a gentle press fit. I slathered it in Loctite Red and pressed it in. Voila! .30-caliber Helwan.

Of course I’d still need to cut the chamber, and ordered a .32 H&R Magnum chamber reamer, which ought to be easy to modify for my purposes. Thank you, Patreon supporters! This is of course the very reamer that did not arrive on schedule today.

Earlier in the week I was dialing in my process for making cartridges. It all starts with the .30 carbine brass.

Sizing the brass using a .32 H&R Magnum resizing die. The case is not straight-walled, and it needs to be.
After running the brass into the die it’s mostly straight-walled, except for a bit at the base. Got to do something about that…
The lathe solves the problem. Of course it wasn’t that simple…

Brass needed to be removed at the base of the cartridge using the lathe, and there was definitely a learning-curve there. It also required making a special mandrel to fit the brass. First batch of five saw three fail, but by the end I was five for five. I wound up with a total of 25 cartridges. Good enough to start.

For test purposes I loaded 78gr LFP bullets over 3.0gr. and, after some consideration and calculation, 3.5gr. of Unique, so I had some loads to test. The goal was to drive a 75gr. bullet at 1150 fps. The math suggested I could drive it as fast as 1200 fps. without creating mechanical issues with the gun, but I saw no reason to push it that hard.

Finished ammo, 78gr LFPs over 3.0 gr. of Unique.

When I discovered that the reamer would not arrive today, and seeing as I had all of this ammo on-hand I sacrificed a .375″ chucking reamer to make my own chamber reamer.

My improvised chamber reamer. It’s ugly, but it works. Mostly. Sort of.

So I used my improvised chamber-reamer until the loaded cartridges fit easily. I used a carbide burr to cut the feed ramp, then cleaned it up with a 400grit sanding drum and a cratex polishing cone.

After tweaking the feed lips slightly the magazine presents the cartridge nicely and they chamber properly.

OK, all ready then. The rounds fit the chamber, they feed from the magazine, they extract and eject manually. Time to shoot. I set up the Caldwell Chronograph. The 78gr LFPs over 3.0 gr. of unique produced 1021 fps. for 181 ft./lbs of energy. Not bad, but far below potential. Now it gets sub-optimal- the gun cycled, but did not extract the fired cartridge. It also didn’t push the slide far enough to engaged the magazine hold-open.

Maybe the 78gr. loaded with 3.5gr. of Unique will have what it takes? Nope. It made 1147 fps. and 228 ft./lbs but again, the cartridge did not extract. On the other hand it showed no signs of excessive pressure, and the gun seemed to be handling it just fine. I decided it was time to be stupid. I loaded some 100gr LFPs over 3.5gr of Unique. This yielded 1086 fps. and 261 ft.lbs. Outstanding… but it still didn’t extract.

After looking over the gun carefully, I think the culprit is a sticky chamber. It is snug, and is not the smoothest so I am going to wait for the proper reamer, which is a few thousandths larger than my home-made reamer.

The 100gr. bullets certainly didn’t lack penetration. They passed through 16″ of Clear ballistics 10% ordinance gel, then through a 4×4 and retained enough energy to do this to a .50-cal ammo can.

When the cartridges extract properly that will change a number of things; the slide will get more momentum transferred to it for one thing. If the pressure is too high when the slide opens it could blow the case-head. I don’t think it will, but it could. Once the chamber is properly finished we’ll see what’s what.

In the meantime if anyone has any .30 Carbine brass laying around that they’d care to contribute…

Michael Tinker Pearce, 29 January 2021

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Baby Dragoon Cartridge Conversion

The Colt Walker allowed Colt to rise from the ashes of his Patent Revolver Company, and in 1848 the new Colt’s first purely civilian revolver was the 1848 Pocket Model, known as the Baby Dragoon.

Colt’s 1848 Pocket Model, known as the Baby Dragoon.

This was a (nominally) .31 caliber percussion revolver built on a small frame. These were provided in a variety of barrel-lengths and could be had with or without the loading-lever mounted under the barrel. They were instantly popular, and these new revolvers and their successors in 1850 (called the 1849 Model) included mechanical improvements that formed the basis for the famous 1851 Navy and 1860 Army models.

Some of these guns were later converted to fire metallic cartridges by gunsmiths, which were typically chambered in .32 Rimfire, but to the best of my knowledge Colt never did factory conversions of these guns.

A Model 1949 Pocket Model reworked to fire .32 Rimfire by an unknown gunsmith.
Colt 1862 Pocket Navy converted to fire .38 Short Colt

Colt did produce cartridge versions of their Pocket Navy chambered in .38 Colt Short, and in modern times conversion kits for the .31-caliber reproductions were made that used the .32 S&W cartridge.

A modern reproduction of a Model 1848 Pocket Model with a .32 S&W Conversion made by Kirst.

These were not exceptionally successful because (many?) .31-caliber percussion revolvers are actually .32 caliber (.320″) and .32 S&W are actually .31-caliber (.312″) Because of course they are. This meant that .32 S&W cartridges fired through the .320 bore often didn’t stabilize well, tended to be inaccurate and produced ‘keyhole’ hits.

When I decided to do my own conversion on an anonymous Italian reproduction I modelled it on the later Colt conversions and chambered it for .32 S&W. To measure the bore I forced an oversized soft-lead slug through the bore and measured it afterwards. The bore came out, as expected, at .320″. I planned on using hollow-base wadcutters to compensate for this; the skirt of the bullet would expand to fill the bore and engage the rifling.

From here I’ll tell the story with pictures-

Here a picture of the gun prior to modification. The .45 ACP cartridge is shown for size comparison.
Here’s the finished gun. The loading lever has been removed and the barrel-lug has been re-sculpted to resemble 19thC. ‘Avenging Angel’ conversions of the 1851 Navy. The ammo shown is factory Remington ammunition.
I elected to leave the barrel full-length (5-7/8″) and left the grip alone, aside from refinishing it.
Here’s the gun broken down. The breech-ring carries a rebounding firing-pin. There is a port cut in the breech-ring for loading; there is no actual gate like there is on the larger-caliber conversions.
With the hammer at half-cock the cylinder can be rotated to load the chambers one at a time. The empties need to be extracted using a separate rod.
Here’s a close-up of the loading port. The gun can be carried with all five chambers loaded by resting the firing-pin between the case-heads.
Normally the rear sight would be located on the hammer-nose, but since I used a breech-ring with a rebounding firing-pin I had to cut that away. Instead I mounted the rear sight on the barrel just ahead of the forcing-cone. This gives a good 5-1/2″ of sight radius, and since the sights can’t move in relation to the barrel accuracy should be pretty good.
The casing is so short the semi-wadcutter cannot be seated to full depth. These bullets are Hornady 90gr. HBWCs. These are loaded over 1.2gr. of Unique.
Unexpectedly all the bullets showed some expansion when fired into Clear Ballistics 10% ordinance gel. The bullets expanded to .320, with expansion at the tip was to an average of .360. That’s not much, but it’s more than I expected.
As you can see the bullet expanded enough to fully engage the rifling.

I fired five shots over the chronograph and into the ballistic gel. They averaged 769 fps. and 118 ft./lbs at the muzzle, with an extreme spread of 36 fps. The bullets all penetrated very close to 13-1/2″ into the gel. I didn’t fire them through denim because, uh… I forgot to.

I’ll need to take it to the range for a good workout, but I’m pretty pleased with how it’s working out. I am going to mount the breech-ring on the breech with screws; very occasionally the breech-ring will move enough to momentarily bind the action.

The gun needed holster, of course. I modelled mine on the simple ‘gun-bucket’ style popular in the 1870s.

The holster is made from 7-8 oz. top-grain vegetable-tanned tooling leather. It’s double-needle stitched with #7 linen cord.
The belt-loop on the back is located to to hold the butt away from the hip for an easy draw.
Here’s the gun shown with an 1860 Army for size comparison.

Addenda

This morning I fired the Remington Factory ammo into the gel. The bullet penetrated 10-1/2″ and wound up nose-forward. As you can see the rifling grooves are quite deep and plain. When measured the bullet had ‘bumped up’ to .320″. Apparently the very soft lead bullet works just fine, at least in the modified forcing cone of this gun. I’ll take it to the range and run some more rounds through it.

Michael Tinker Pearce, 28 January 2021

7.8x19mm. Because, uh, Reasons.

What the world really needs is a .30-caliber pistol cartridge that, while more powerful that .32 ACP, is not so powerful that it requires a locked breech…” said no one ever. Not even me, and it’s my idea. It’s not even a new idea; the French had a .32 service cartridge that was rather similar. Hmm… better run it through the Wildcatter’s Checklist:

*Does it duplicate the performance of an existing cartridge? Check!

*Does it answer a question no one is asking? Check!

*Is it a pain in the butt to make? Check!

*Is it of dubious utility? Check!

*Will it be fun? Check!

Oh look, a perfect score! I guess we’d better get on with it then. Ladies and Gentlemen, I give you… drumroll please… the 7.8x19mm Auto!

75gr LFP and 65gr JHP versions, though I’m contemplating a 100gr bullet as standard. Have to see what I can come up with…

A couple years back someone gave me some .30 carbine brass, and it was inevitable that I’d find something to do with it sooner or later. Shortened and resized is turned out to be a pretty perfect donor-cartridge for the 7.8x19mm.

Umm… why 7.8mm? Well, because it turns out the .308 bullets are actually 7.82mm in diameter, not 7.62mm. No, I don’t get it either, but that’s the way it is. OK, why 19mm long? Because for the methods I had on-hand it was easy for me to shorten them to that length. I was shooting for 20mm and got 19 and said, “good enough.”

Of course I’ll need some way to test it, and as it happens I have a Maadi Helwan pistol converted to a .380 ACP straight-blowback already, and guess what new cartridge fits in a 9mm Helwan magazine?

Yep, the 7.8 fits in a 9mm Helwan/ Beretta M1951 magazine. It also cycles from the magazine, chambers and extracts from the .380 barrel.

OK, the 7.8 fits in the magazine, and it feeds, extracts and ejects from the .380-chambered barrel. So if I bore out the barrel, line it with a .308 barrel liner and cut the chamber for the new cartridge it just might work…

The goal here is to see if I can drive a 100gr. bullet to 1000fps. and still operate safely as a straight-blowback. This will yield 222 ft./lbs of energy at the muzzle, and the bullet’s high sectional density ought to give it excellent penetration, hopefully even with an expanding bullet.

The stock 9mm magazine positions the bullet well for feeding into the chamber, the extractor holds the case well and the ejector kicks it out. Now all I need is the right caliber barrel…

As it happens I have a short section of .308 barrel and some Speer 100gr. .308 Plinkers. I also have a .308 resizing die I use to resize .312-caliber bullets to .308 for use in my Mauser C96 broomhandle. This is a totally doable thing…

Of course the question of whether one should do a thing just because one can comes up… to which I say, ‘Why the hell not?’ It’ll be fun, and if it doesn’t work out I can always get another barrel for the Helwan and turn it back into a .380, or even get one of the new locking blocks from that fellow in Europe and restore it to 9mm.

So is this new cartridge going to set the world on fire? Uh, no. The world manifestly does not need this cartridge. I expect I will go to my grave as the only person to own a firearm chambered for it, in fact. But it will be fun, and that’s really the whole point.

Naturally whatever happens I’ll keep you posted.

Michael Tinker Pearce, 23 January 2021