I've just updated my web article looking at the pros and cons of bullpups: http://www.quarry.nildram.co.uk/bullpups.htm
I will at some point extend the final paragraph to include an analysis of the benefits of long barrels when designing future ammunition. These thoughts were prompted by some work done by a gun experimenter with a hacksaw, who kept chopping more and more off a barrel of a .300 Win Mag to measure the result in muzzle velocity. Interestingly, he concluded that the MV of the magnum from a 16" barrel would be the same as for the same bullet fired by a .308 Win from a 24" barrel - only at the cost of bigger and heavier ammo developing lots more recoil and muzzle blast.
The significance of the 8" difference in barrel length is of course that this is about the same as the difference in overall length between bull pups and traditional rifles with the same length barrels. Or to put it another way, the performance of a .308 bullpup will match that of a traditional .300WM when the guns are the same overall length.
Now it could be argued that no-one in his right mind would think of firing .300 Win Mag from a 16 inch barrel (though I wouldn't bet against it - you can buy 5.56mm carbines with barrels of around 8") so I did some more digging and discovered that you can more or less match the velocity of 7.62x51 from a 13" barrel (as used in the SCAR H carbine) with the .302 Whisper (7.62 with the case cut short to 38mm) fired from a long rifle barrel.
The conclusion is therefore that deciding to design any new military cartridge (to meet whatever ballistics are required) for a bullpup rather than a traditional rifle allows you something like a 50% increase in barrel length, which means that the cartridge can be smaller and lighter, will develop less recoil, and produce much less muzzle blast, requiring a much smaller suppressor.
Not that I'm expecting the US Army to change it's antipathy towards bullpups, but it does demonstrate that the current fetish for ever-shorter barrels has a significant cost.
I will at some point extend the final paragraph to include an analysis of the benefits of long barrels when designing future ammunition. These thoughts were prompted by some work done by a gun experimenter with a hacksaw, who kept chopping more and more off a barrel of a .300 Win Mag to measure the result in muzzle velocity. Interestingly, he concluded that the MV of the magnum from a 16" barrel would be the same as for the same bullet fired by a .308 Win from a 24" barrel - only at the cost of bigger and heavier ammo developing lots more recoil and muzzle blast.
The significance of the 8" difference in barrel length is of course that this is about the same as the difference in overall length between bull pups and traditional rifles with the same length barrels. Or to put it another way, the performance of a .308 bullpup will match that of a traditional .300WM when the guns are the same overall length.
Now it could be argued that no-one in his right mind would think of firing .300 Win Mag from a 16 inch barrel (though I wouldn't bet against it - you can buy 5.56mm carbines with barrels of around 8") so I did some more digging and discovered that you can more or less match the velocity of 7.62x51 from a 13" barrel (as used in the SCAR H carbine) with the .302 Whisper (7.62 with the case cut short to 38mm) fired from a long rifle barrel.
The conclusion is therefore that deciding to design any new military cartridge (to meet whatever ballistics are required) for a bullpup rather than a traditional rifle allows you something like a 50% increase in barrel length, which means that the cartridge can be smaller and lighter, will develop less recoil, and produce much less muzzle blast, requiring a much smaller suppressor.
Not that I'm expecting the US Army to change it's antipathy towards bullpups, but it does demonstrate that the current fetish for ever-shorter barrels has a significant cost.
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