View Full Version : Theoretical cartridge question.

March 17, 2005, 06:22 PM
I have seen a move towards armor piercing rounds in SMG's recently(H&K MP7 PDW (http://world.guns.ru/smg/smg49-e.htm) and FN P90 (http://world.guns.ru/smg/smg13-e.htm) f.eks., as well as the recent sweedish PDW), but I have also read a lot of articles by gunwriters questioning the stoppingpower of the 4.6mm HK round, and the 5.7mm FN round, because of low energy/low diameter(The FN p90-round has about as energy from the P90 as a 9mm+p from a pistol. The H&K round even less).

The problem with the .223 compact carbines(I'm not thinking of the M4, but the even shorter barreled supercompact XM-8, or HK G36C) is lack of velocity, and as a result the bullets don't fragment, and this hurts stoppingpower(ice-pick like performance). The problem with the 9mm, .40s&W and .45acp guns, is the lack of armor piercing abillity, and lack of effective range due to more rainbow-like trajectory.

This got me thinking. What if you put a somewhat longer .355 diameter spitzer-bullet in .357 SIG brass, with a steel or tungsten tip, and a small circular cavity around the steel/tungsten tip, like a conventional hollowpoint, so that it would both penetrate soft body-armor, and expand if hitting an un-armored enemy. Also, in the longer barrel of an SMG, the high pressure of the .357 sig would result in a larger gain in velocity(Just as f.eks. the .357 magnum, which practically doubles it's energy from revolver to carbine because of the longer barrel), and thereby more energy than any conventional SMG, or even the fine-caliber HK and FN guns. Also, a longer spitzer-bullet will maybe result in better ballistics, and better sectional density. At least, that's the theory. :)

So, what I'm wondering about is if this, in theory, would be plausible for use in either a slightly modified(rechambered and new magazine) conventional SMG like the H&K UMP (http://www.amazon.com/exec/obidos/tg/detail/-/0060586109/qid=1110901703/sr=8-4/ref=pd_csp_4/103-0523630-5272630?v=glance&s=books&n=507846 ) or in a theoretical SMG designet around this round, and with a Calico (http://world.guns.ru/smg/smg57-e.htm) or PP-90M1 (http://world.guns.ru/smg/smg59-e.htm)-like helical magazine. A helical magazine would give the gun even more ammo per magazine than the FN P90. I am not thinking of this round for use in pistols, only in SMG's and PDW's.

So, give me input people. Inform me of anything I have overseen, anything that speaks against this solution, or anything you think could improve upon this. Also, if you think this is a good solution, I want to hear it too.


Jim Watson
March 17, 2005, 07:44 PM
I think the Soviets did some work along that line. You would have to be using a lot of subguns and pdws for it to be worth the expense of development and deployment.

March 17, 2005, 08:09 PM
A .357 Magnum through a rifle has more muzzle-energy than a .223 through a M4-lenght barrel. A .357 sig isn't a .357 magnum, but with the right load it could easily equal a .223 from a M4 energy-wise. While it wouldn't match the .223's ballistics, a spitzer-bullet would make it far better than the other pistol-calibers, and with either a fragmenting bullet or hollow tip(hollow, but covered with copper) around the steel/tungstein core, I think it would have far better stoppingpower than the .223 with M4-barrel lenght velocities. And it would have far less muzzle-blast.

I don't think it would be too hard to make this work in existing SMG's, but I'm not thinking about this as something someone would really do. It's just a thought experiment about better filling the gap between assault rifles and SMG's, and how to accomplish this. :)

March 27, 2005, 11:26 PM
There is a special sabot round for the 7.62x25 tokarev called the .223 Timbs. Obviously it uses a .223, but it will also produce simmilar velocities from a CZ 52 as a m-16 with a 7 inch barrel. The only configuration is with a 55 gr. hollow point, but i suppose you could have some remade for an AP round like you are suggesting. And while it's still the .223 bullet, you're not wasting a whole cartrige to get the same effect. As an added bonus, you could just make a pistol that accepts a detachable stock like they used to use so that you don't have a whole rifle to lug around.

March 28, 2005, 12:10 AM
I saw one of those sabot rounds. Guy was in the shop looking for the sabots so he could reload, rather than paying a dollar a round. Can't remember if it was hollow point or not, but if you have the tools, putting a FMJ in there instead wouldn't be a problem.

Talking there, made me think of what a .500 would do with a .30 sabot round.

March 28, 2005, 12:31 AM
Well, the PP-90M1 or Bizon both only have 45-round helical magazines for the large/punchier 7.62x25 (TT, not Mauser) rounds. So it's not some panacea for mag capacity.