This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons.
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This was clearly originally designed to be a PDW cartridge And I think it actually fulfills the requirements with long bullets and rather ridiculous amounts of energy. (E0 is 1144J, E100 is 700J). In the spirit of overreach, should one consider this?
It is noteworthy that major armies have shown little interest in the 4.6 mm HK and 5.7 mm FN, but are still persevering with 9 mm as the next step down from 5.56 x 45. That suggests that interest in small-calibre HV PDW rounds is low.
1) .300 BLK, more suited for 10" barrels or shorter
2) crazy idea: a much heavier, longer (30mm?) and slower 5.56 bullet. Less propellant, less energy, less recoil. Maybe 1300J?
this thing creates 1200J out of a 5" barrel. Which is just ridiculous ;o) I have been thinking about a successor to the 30 carbine and I thiink this is it. Now can I please have an MP9 in this cartridge? And what on earth is the pressure? And it is clearly an incredibly progressive powder.
But 7.5mm is not that small a calibre. And the solid copper round (95gr) penetrates IIIA at 20m.
It's a shorter and fatter BLK300. 9.7 mm case head by 35 mm compared to a 10.8 mm case head by 27 mm. With only 8 mm for the projectile it is a terrible round ballistically. Increase the barrel length to 10" and the OAL to 40 mm and it would be similar to the BLK300 in a round that would just barely fit in a pistol grip magazine.
The round is way longer than 8mm - if it was 8mm, it'd not be in the case.
The round actually retains velocity rather well, with:
Muzzle velocity: 610 m/s (2000 fps)
Velocity at 100 m (110 yds): 465 m/s (1525 fps)
Muzzle energy: 1144 J (844 ft/lbs)
Energy at 100 m (110yds): 700 J (520 ft/lbs)
Muzzle velocity: 610 m/s (2000 fps) Velocity at 100 m (110 yds): 465 m/s (1525 fps) Muzzle energy: 1144 J (844 ft/lbs) Energy at 100 m (110yds): 700 J (520 ft/lbs)
Compared to losing 100 mps over 100 metres like the 300 AAC? No it's a terrible round. The 300 AAC has 21 mm for the ogive unlike the 8 mm of the 7.5 FK.
But it is not a handgun or machine pistol round - it is a round for carbines with 10" barrels. Rather a diffrent critter. The comparison for the 7.5 FK is the 9x19. You're comparing apples with crayfish.
"This was clearly originally designed to be a PDW cartridge And I think it actually fulfills the requirements with long bullets and rather ridiculous amounts of energy. In the spirit of overreach, should one consider this?"
No. The 7.5 FK is a bad idea. It is outranged by the calibers most likely to be encountered (5.45x39 and 7.62x39).
Plus, no army seems interested in a PDW, opting to use pistols, submachine guns, and SBRs for personal defense.