7.8 x 19mm. Again. Yeah, yeah, I know…

I promise I’ll talk about something else for, uh, a while! But for now here’s the update. I have finally been able to make a decent amount of ammunition thanks to Brena Bock, who sent me 100 or so .30 Carbine cases. I have the conversion process pretty much down to a science at this point.

7 yards, ‘Chasing the Bullet’

I finally managed to get to the range to try the gun out, and there was good news and bad news. The bad news is the 78gr. bullets nose-dive instead of feeding if you load more than five rounds in the magazine. The good news is the 100gr. bullets cycled 100%. Mind you, I fired about fifty rounds total, but it’s looking good.

Since I didn’t know where the gun was hitting I ran a blank target out to seven yards and played ‘Chase the Bullet.’ I fire a shot to a more-or-less random location on the paper, and that becomes my aiming point for the next shot. After that each new bullet hole becomes the aiming point. This pretty quickly tells me where the gun is hitting in relation to the point-of-aim; in this case slightly high and slightly left.

The gun is quite pleasant to shoot. The trigger isn’t special, but it’s OK, and recoil is very light indeed. It shoots like, well, it shoots like a semi-automatic pistol. While I wasn’t focused on accuracy it isn’t conspicuously inaccurate.

100gr. Hard-cast lead flat-points. The gun likes these quite a bit.

Loading with Unique turns out to be very simple. Load 3.5gr of Unique and put a 100gr. bullet over it. Pretty much any 100gr bullet, apparently. I tried the 100gr LFPs, 100gr. Speer HJLRN (Plinkers) and 100gr. XTP JHPs. All of them work fine over 3.5gr. of Unique.

Here’s how they stack up. I’m not listing the Extreme Spread (ES) because I fired relatively few shots, and they were all quite close in velocity. I want to get some more data before posting the ES.

100gr LFP, 3.5gr. Unique, CCI500 primer

914 fps. 185 ft./lbs.

100gr HJLRN (Speer Plinker,) 3.5gr. UniqueCCI500 primer

890 fps. 176 ft./lbs

100gr XTP HP, 3.5gr. Unique, CCI500 Primer

941 fps. 197 ft./lbs

I’m not sure why the Speer Plinkers were so much slower than the other bullets. The XTPs, as predicted, did not expand at all when fired through denim. All three bullets penetrated 13 to 14-1/2″ into the Clear ballistics 10% ordinance gel through four layers of denim.

Three test bullets, from left to right: XTP JHP fired through denim, XTP JHP fired into bare gel and a Speer Plinker fired through denim.

That’s it for Unique, because 3.5gr. is about all that will fit in the case; in fact this is a slightly compressed load. So there we are, unless I can come up with lighter bullets that are long enough to feed reliably. I actually have an idea about that; I’ll have to try it and see if it works out.

That’s not the end of load development of course; Unique is only one kind of powder. I found a pair of videos on Youtube where Duelist1954 was developing loads for 7.5mm French Long, which is pretty similar to 7.8 x 19mm. In it he used Unique, Power Pistol and Blue Dot. I happened to have a tiny bit of Power Pistol on hand, but it was enough to run a few test shots over the Chronograph. The results were gratifying-

100gr LFP, 4.2gr Power Pistol, CCI500 Primer

1028 fps. 235 ft./lbs

This meets my original benchmark of a 100gr Bullet at 1000+ fps. The bullet penetrated 20″ of gel when fired through denim and the cases again showed no signs of excessive pressure. I’d like to test a different HP, a ballistic-tipped round and maybe the 90gr. Lehigh Extreme Defender, but with the current shortages that probably won’t happen soon. For now it’s time for another range trip to try the various loads for accuracy.

OK, Why is This Working?

It’s occurred to me more than once that these are running awfully hot for a straight blowback. It might simply be that this gun has significantly more mass in it’s slide than a typical straight-blowback .32 0r .380 ACP. It’s also possible that since the barrel moves about a 1/4″ to the rear before it stops and the slide continues on it’s own that maybe that slight delay is just enough? Or maybe it’s a combination of these two things, or some third thing I haven’t thought of. I just don’t know. Whatever is going on it works better than it has any right to, and I’m glad of that!

I’ll be taking a break from the 7.8 x 19mm for a while. Get to the range, test some more stuff etc., but that’s for another day. Other projects have languished while I fiddled with this and they are calling out to me.

Michael Tinker Pearce, 11 February 2021

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