When, the 34th Michigan was moved up into position at Santiago, Cuba, they were armed with .45-70 Springfield Rifles.

The Regulars instructed the Michigan Volunteers to "cover our flanks and rear".
They also advised the Michiganders ... "and don't shoot those damn things".

The day before, the 71st New York had fired their Black Powder Trapdoors and brought down a rain of Spanish Artillery and 7mm rifle fire on the American positions, 'marked' by white smoke.

From what I can gather, the State Volunteer Units did not bring their State's arms, but, received Federal weapons in the Federal Camp locations, where they were concentrated.
('Trapdoors' were issued at Camp Alger, in Virginia, to the 33rd & 34th Michigan Vol. Inf. They drilled and did guard duty with wooden 'clubs' until finally issued the .45-70 rifles).
It would have been a very lucky or 'connected' State Volunteer Unit that got Krags for the Santiago Cuba Campaign.

The Black Powder smoke did draw fire and increase U.S. casualties.

IMHO - During the SAW, it probably didn't matter how modern a State's arms were. The guns were probably left back in the home state, when the men sworn into Federal Service were shipped to Federal Camps.