Reversed Bullets

I heard tales of these from WWI stories as an attempt at better penetration of thin armor plating by anti-tank riflemen. The bullet (I'm unsure what the construction was of anti-tank bullets in those days. FMJ? ) was seated pointed side in and fired with an increased charge. The theory was that a wider meplat transfers its energy to the target (in the form of shearing a hole) more efficiently than a pointed bullet which delivers a softer impulse to the target as it deforms from the initial point contact.

Rather than ask whether it really works (it's been done to death) I wanted to ask if anyone's tried it. I've become interested in 223 case-head sub-caliber wildcats of late, and my idea was seating a reversed 30 Tokarev FMJ round nose bullet backward.

The case would be an elongated 7.62x25 case with the flat bullet seated flush with the (short) neck. The OAL would match the current x25 OAL. My thinking is the shoulder could be pushed forward by the amount the bullet currently protrudes (quite a large portion of the length of the 7.62x25, btw) and that having the taper, rather than the flat base, inside the case, would not displace as much powder volume.

You'd get another 10-20% of powder volume with no change in envelope (I think). So long as the round remains well above sonic velocities, the stability of the round should not be an issue (the weight is up front so it's actually more stable), and if that speed can be held for a couple hundred yards (which the extra powder should help ensure) the poorer ballistic shape shouldn't drastically effect accuracy either.

Because of the neck-taper of the round, it might still feed as easily as a hollowpoint if the mouth were crimped onto the round even slightly. I suppose that necking the round down further to .25 or even .224 would feed even better, so long as the neck can be kept short. True wad cutters or simple bullets made from brass rod (in rifles only ;D) could be used as well.

We're all aware of the benefits of heavy wad cutter loads from revolvers; why not obtain them for auto loaders?

TCB

Here's a diagram of what I attempted to describe initially. Hopefully this better demonstrates the supposed "advantage" I thought a setup like this could possibly achieve. Any impact on penetration or energy transfer would be purely ancillary. The goal is to bump up the capacity in a 7.62x25 envelope (for fitting in existing magazines and bolt faces) in an attempt to get the 30cal bullet up into "light carbine" power levels, as opposed to pistol levels. The lower end of what we consider 30 carbine type rounds (kinda halfway between handgun and rifle rounds).



As you can see, the bullet is seated flush, or nearly so, so the forcing cone issue would be a non-issue (they'd contact the leades at the same position). Since the flat point is close to the pronounced shoulder, the shape should still be able to feed about as well as a hollow-point straight-wall case (I think). According to the laws of physics, the pressure in the case would still act on the same net area of the bullet before, so it's not like the energy transfer there would be different. I'm more concerned about what impact the full length of the bullet's contact surface scraping over the case neck will have on it. I'm also curious an FMJ loaded upside down in a high-pressure cartridge is even safe, or if the "guts" would get squeezed out the front. More an issue for lead core than Tok steel core stuff.

For distances where the round remains well above sonic, the shape of the nose actually has very little impact on aerodynamic stability, compared to the benefit of having the center of mass shifted forward. Transonic performance would suck, but that's why the extra powder is used to keep it above water a bit longer. My hope would be good performance out to 200yds (should be easily attainable) since this would be a light carbine round. The Tokarev Long, or Tokarev Magnum, or 300 Zephyr, 300 Brown-Out... whatever

TCB

Yup, the broader contact area imparts greater shear force to the steel plate before the bullet splatters. Apparently British tanks could be penetrated on occasion by German riflemen this way. Like I said, though, merely a nice side benefit of what I wonder is a way to increase powder capacity a bit within the same overall length

TCB

Okay, maybe I didn't explain my motivations clearly; penetration is not the goal of this exercise, but increased powder capacity. Does anyone know if reversing an FMJ or HP in full power loads is dangerous? The WWI rounds were, but they were also much higher pressure loads--I would obviously be saner in my formulas.

TCB

The case holds 16gr at present. With the bullet turned backwards, or simply replaced with a cylindrical so it can be gripped by the neck at the front, the case neck can be moved forward the amount the bullet used to protrude (to get the same crimp engagement). So the case volume would increase a good bit, and the tail of the equal weight bullet sticking further inside would displace a portion of the increase in volume.

"The problem before you is how to maximize velocity while keeping pressure within acceptable limits."
A net increase in the amount of powder that could fill the case, for a round that still has the same overall length. Because volume increases, peak pressure will last longer, and accomplish more energy transfer without additional load on the bolt. x25 maxes around 35ksi, IIRC, and if made from 223 brass, should be capable of comfortably operating up to 223 pressures, if so desired (obviously a locking breech would be required)

If tok is 16gr, and 30 Carbine is 21gr, I imagine my weird little round would be something like 18gr. Just a bump, sort of like an Ackley Improved wildcat, only one where the factory chamber reamer is simply run deeper into the barrel. The x25 has a very large length of bullet protrusion for it's size. I'll have to model it in CAD to see how much actual volume is gained, but it will be a narrow ring of powder around the base of the bullet inside the case. It might have strange burn characteristics that result in soot or a long pressure peak, but it would deliver more power to the bullet.

My main question was whether anyone has heard of any inherent safety issue in trying to seat a bullet past the neck (without increasing powder density, of course). The "reverse bullet" thing was merely the inspiration, and its performance implications obviously a distraction from my inquiry . Every wildcat of "typical" layout based on the 223 case head has been done to death already; I kind of figured someone had tried this by now

PPSH 41 mags and a locking breech tube gun

A huge number of rounds fit and feed from the PPSH mags and drums (7.62, 9mm, 40, 45 with mods, and their wildcats like 9x21, 10mm, 45 Win Mag). As with the others, my hope is that merely stretching the tok case will make for a stouter wildcat like the others, but still use the same case head. 30 carbine is about 1/8" too long, and is so narrow the reverse trick would severely limit powder capacity.

TCB