justin22885
member
- Joined
- Nov 9, 2009
- Messages
- 2,102
aah, i think i get it.. but.. what would be the primary benefit of this?
Last edited:
designing a rifle and would like some input
- Thread starter justin22885
- Start date
- Status
justin22885
member
- Joined
- Nov 9, 2009
- Messages
- 2,102
ive never been too impressed with 5.7x28.. it seems to be really underpowered for what it COULD be.. also, the base diameter of the case is a bit odd.. not easy to find brass for.. now what would be really cool is creating a new cartridge based on the .223 case.. basically just shortened .223 down to 40-41mm, youd have more case capacity than the 5.7, same bullets, more power, and you can chop and shape common 223 brass
check out this cartridge.. starts out as .223 brass, then its trimmed and necked down... case length is 28.4mm, overall length of 41mm with a case volume of about .075 cubic inches.. ballistically this would be about the same as the .221 fireball cartridge which produces about 1,000ft/lbs energy in a 14" barrel and would be small enough to chamber in a autoloading pistol.. do the same thing with the same bullet starting with a .308 cartridge (same base diameter as 45acp) and youd have the same case volume as a .223, so balistically your cartridge that would be no larger than a 44 mag would have all the energy of a .223 firing from an autoloading pistol
check out this cartridge.. starts out as .223 brass, then its trimmed and necked down... case length is 28.4mm, overall length of 41mm with a case volume of about .075 cubic inches.. ballistically this would be about the same as the .221 fireball cartridge which produces about 1,000ft/lbs energy in a 14" barrel and would be small enough to chamber in a autoloading pistol.. do the same thing with the same bullet starting with a .308 cartridge (same base diameter as 45acp) and youd have the same case volume as a .223, so balistically your cartridge that would be no larger than a 44 mag would have all the energy of a .223 firing from an autoloading pistol
Last edited:
barnbwt
member
- Joined
- Aug 14, 2011
- Messages
- 7,340
It's called 22TCM, I believe. On paper, it's superior to 5.7, but uses pathetically small expanding bullets as opposed to fragmenting long-ogive projectiles. I think 22TCM with the same actual Vmax bullet characteristics as 5.7, but loaded to 223 pressures (would obviously need to be made of the same actual brass) would be incredibly effective, though perhaps not from a very short and light weapon. 
The primary reason 5.7x28 can't get much hotter is because it's fired exclusively in blowback and semi-delayed blowback guns (P/S90 and five-seven, respectively). Any higher in lighter platforms, and you get case separation as the case extracts under pressure.
The real shortcoming to 5.7 (that comes with a matching benefit) is the primer pocket is HUGE compared to the case head, so it can swell and loosen under high pressures much more readily than a small primered 9mm, for example. Makes reloading a low-reuse proposition (Teflon coating doesn't help, either). The benefit is the case is narrower (I think) than even a 32acp, making it extremely unique in terms of capacity. The five-seven holds 20 rounds, which isn't that impressive, but this is mostly due to the size the gun happens to be. Though the round may be X% smaller, that doesn't translate into X% higher capacity since we have to round down to the nearest whole round. A mag much larger has significantly more capacity (the 50rnd P/S90 mag), and I imagine a mag a bit smaller would be very high capacity for its size (for example, I'll bet about 10 rounds would fit in my currently 7-round R51 mags if they were .05" longer --that's a nearly 50% increase!)
TCB
The primary reason 5.7x28 can't get much hotter is because it's fired exclusively in blowback and semi-delayed blowback guns (P/S90 and five-seven, respectively). Any higher in lighter platforms, and you get case separation as the case extracts under pressure.The real shortcoming to 5.7 (that comes with a matching benefit) is the primer pocket is HUGE compared to the case head, so it can swell and loosen under high pressures much more readily than a small primered 9mm, for example. Makes reloading a low-reuse proposition (Teflon coating doesn't help, either). The benefit is the case is narrower (I think) than even a 32acp, making it extremely unique in terms of capacity. The five-seven holds 20 rounds, which isn't that impressive, but this is mostly due to the size the gun happens to be. Though the round may be X% smaller, that doesn't translate into X% higher capacity since we have to round down to the nearest whole round. A mag much larger has significantly more capacity (the 50rnd P/S90 mag), and I imagine a mag a bit smaller would be very high capacity for its size (for example, I'll bet about 10 rounds would fit in my currently 7-round R51 mags if they were .05" longer --that's a nearly 50% increase!)
TCB
barnbwt
member
- Joined
- Aug 14, 2011
- Messages
- 7,340
"so balistically your cartridge that would be no larger than a 44 mag would have all the energy of a .223 firing from an autoloading pistol"
It would likely be higher, being a stubbier case (read: the WSSM fad a few years back. The portly cases did deliver higher velocities for the same powder/pressures, but the increased case head area rapidly ate up numerous actions' bolt thrust capacity; there's no free lunch, even if you don't care how big your magazines will have to be.)
TCB
It would likely be higher, being a stubbier case (read: the WSSM fad a few years back. The portly cases did deliver higher velocities for the same powder/pressures, but the increased case head area rapidly ate up numerous actions' bolt thrust capacity; there's no free lunch, even if you don't care how big your magazines will have to be.)
TCB
justin22885
member
- Joined
- Nov 9, 2009
- Messages
- 2,102
oops, i forgot to actually post the rendering of the cartridge, i posted it above
ive looked at the .22tcm, i just wish it didnt try so hard to fit within a 1911 size action while providing little more ballistically than the 7.62x25mm which can be incredibly hot, and much cheaper.. when trying to get as much power into a handgun as you can.. to have a cartridge thats quite powerful in a short 10" or so carbine, you have to make as much use of the spaces you can.. so why limit yourself to a 32mm cartridge when the average hand can comfortable fit over a magazine holding 40mm cartridges?
ive looked at the .22tcm, i just wish it didnt try so hard to fit within a 1911 size action while providing little more ballistically than the 7.62x25mm which can be incredibly hot, and much cheaper.. when trying to get as much power into a handgun as you can.. to have a cartridge thats quite powerful in a short 10" or so carbine, you have to make as much use of the spaces you can.. so why limit yourself to a 32mm cartridge when the average hand can comfortable fit over a magazine holding 40mm cartridges?
Last edited:
justin22885
member
- Joined
- Nov 9, 2009
- Messages
- 2,102
you know.. i could use that cartridge above in my revolver.. could even make that a gas seal if i wanted to extent the neck of the case out over the bullet.. imagine that in a revolver
but..after doing a little research it seems this thing will equal the .221 fireball in performance out of similar barrel lengths, which in itself equals the .223 in 14 inch and shorter barrels (where the 223 just blows the excess powder out the barrel anyway).. so this cartridge in a 10-12" carbine would perform about the same as a 10-12" AR-15 and surpass the 5.7x28 in a pistol.. would be great for a PDW and sidearm of greater performance to the 5.7, and much easier to get ammunition since its just made from 223 brass
this may sound odd but i actually had a dream where i was using the cartridge shown above in a carbine like the one shown by jim on the last page that took magazines in the grip
but..after doing a little research it seems this thing will equal the .221 fireball in performance out of similar barrel lengths, which in itself equals the .223 in 14 inch and shorter barrels (where the 223 just blows the excess powder out the barrel anyway).. so this cartridge in a 10-12" carbine would perform about the same as a 10-12" AR-15 and surpass the 5.7x28 in a pistol.. would be great for a PDW and sidearm of greater performance to the 5.7, and much easier to get ammunition since its just made from 223 brass
this may sound odd but i actually had a dream where i was using the cartridge shown above in a carbine like the one shown by jim on the last page that took magazines in the grip
Last edited:
justin22885
member
- Joined
- Nov 9, 2009
- Messages
- 2,102
the second rifle design i was working on.. not the one ive been discussing here but a short-recoil model ive been working on ive decided to stop working on.. its operation would be too similar to this pistol/pdw/carbine idea im working on now since it too will be short-recoil.. but i think ill start a separate topic in the autoloading pistol forum
- Status
