From Knute's last post:

"A so called rifle without rifling was also tested and gave good results".

FWIW - This is likely a reference to "Cole Rifling".

Dr. W. F. Cole, of Waco, Texas, applied 'Lancaster Oval-Bore Rifling' to small-bore barrels for metal-jacketed bullets.

A test of Cole rifling was conducted at Springfield Armory in July, 1902. Four model 1898 rifles were fitted with Cole barrels with one turn in 10" rate of twist.

They gave slightly better accuracy than service barrels at ranges up to 500 yards. A twist rate of one turn in 8" was also tested.

Apparently, accuracy improvement was not significant enough to merit adoption.