drew458 sent me a copy of the original blueprint/dimensional schematic of the .280 brit cartridge, which i have written extensively about. not so long ago i developed a wildcat "jj's brit," with considerable input, comment and help from brit.
i make and load the wildcat, and have shot it in a rifle composed of my "lumber lower" and a conventional upper receiver, and functioning is very good, once the magazines get a little wear and slickening on them.
the original brit is very close to what i/we cooked up, so close that i am convinced that the brit would function very well in an ar-15, by the simple expedient of loading a relatively light bullet deeply into the case, not to exceed the nominal overall length as established for ar-15 rifles.
i think it a cartridge superior to the various .264"/6.5mm concoctions, for the purposes of close combat and for combat in the 300 to 400 yard range. for some purposes the 6.5's are pretty good, especially long to very long range target shooting. but, for combat, the brit is probably better.
6.5 enthusiasts should temper their enthusiasm a bit for the 6.5's as combat rounds, by a simple application of memory and historical judgment. huh?, you say. well, and the turn of the 19th century into the 20th (from the 1890's into the early 1900's), the 6.5mm cartridge was all the rage as a combat round, having been adopted roughly in that period by italy, austria, japan, portugal, sweden, i think perhaps roumania, and i think a couple others, which escape me. and, the united states navy adopted a far seeing rifle, the 6.5mm lee navy only to take it out of service with the adoption of the 7.62 krag jorgenson.
of those countries all of them switched to larger caliber rifles and/or loadings because the 6.5mm's lacked sure lethality, and the inability to immobilize an enemy with slightly marginal wounds. in simpler terms, the 6.5's lacked the killing power wanted by the armies using it. (and, the u.s. navy, for much the same reason.)
these countries went to larger caliber rounds, mainly the .308, .311 and .323 diameter rounds. and, when some of those countries adopted smaller rounds with lesser ballistic performance than what is now described as the "main battle rifle," even though adopted smaller cases with lesser powder charges, they stuck with the larger diameter & heavier bullets.
well, what difference does it make, you may ask. having never been shot with any of the rounds under discussion, i cannot lend you any reason based upon personal & anecdotal experience, i can only tell you what the military powers of the major combatant nations of the world did. and, that is clearly, that they abandoned the 6.5mm diameter bullet as a combat round, for the reasons stated.
some countries, denmark being a prime example, kept the 6.5mm round in the krag rifle for target shooting, which moving to an 8mm round & rifle intended for combat use, in the same rifle. it is difficult to conceive of any clearer example on the part of military thinkers that they viewed the 6.5mm bullet as insufficient to perform as desired in the fields of combat.
japan attempted the switch to a 7.7mm round during wwii, and italy attempted the same, adopted a 7.35mm round. portugal switched to the 8mm german round before wwii, though not involved in wwii but having considerable experience in her colonial possessions. sweden is the only country that i know of which used the 6.5mm through wwii, but, they never used the round in actual combat.
and, i would note, that the u.s. army though considering the adoption of a new service round, is likely viewed as adopting a 6.8mm round (.277 caliber, the same as used in the .270 winchester civilian round.) well, that's it.
have a nice day, and thanks for the read, if you got this far.
john jay @ 10.10.2019