It's been done:
25 Remington...factory chambering in 1906---equivalent and ballisticall identical to the 25-35
Factory ammo was discontinued in 1950
And then it was re-done:
http://www.68spc.com/history.php
".....After a lot of work on the 7.62, they started with the 30 Rem cartridge as a basis for a totally new cartridge and tried the basic combination with a variety of bullets including: 25 cal, 6mm, 6.5mm, 6.8mm(270) and 30 cal."
This is an exerpt of the origins of the 6.8SPC
If you want a harder hit with just a barrel swap..look into 6x45
No differrent mags or anything from a standard AR...just a different barrel.
This was the cartridge that the M249 SAW was designed to shoot.
60 grain bullets at 22-250 velocity and 100 grain bullets at 3000ft/sec
EDIT: Woops 100 grain bullet at 2700ft/sec...should have checked...sorry
The largest I shoot is 80's at 2900ft/sec
Not quite a quarter bore....but the 25TCU is the same thing just in 25 cal.
Threaded Mode