The combat period against the Moros in the Southern Islands lasted from 1899 until 1913, and saw three major combat rifles in use on the side of the Americans. There were of course, also pistols, bayonets and shotguns utilized by American forces during this period, and one of the most famous pistols of all time, the John Browning designed 1911 came about due to a desire for increased stopping power over the issue .38 revolvers then being used against the Moros. Due to the rifle's prominence as the main line infantry arm, however, I will focus on those in this entry.
At the beginning of the period, U.S. Volunteer Forces and State Troops were still armed with Single-Shot 'Trapdoor' Springfield Rifles. To fire this arm, the trooper flipped up the breechblock, inserted a .45-70 cartridge, flipped down the block, took aim, and fired. I have seen many sources give the rate of fire for this arm at 10 rounds a minute. Despite some trying, I have never reached that level of speed with a trapdoor. On the other hand, I have never had a screaming, kris-wielding, Juramentado running at me with murder in his eyes. Perhaps urgency is required for such a level of speed. In any case, the old trapdoors were fine combat arms, posessing a powerful round with excellent stopping capacity, and fine accuracy. Also, it was a solid, reliable, and simple arm, well suited to combat and poor conditions. The strong, rigid weapon also was a good platform for fighting with a mounted bayonet, something later service rifles did with decreasing potency.
U.S. Regulars, at the beginning of the conflict, were largely armed with the elegant Krag-Jorgenson rifle. Slightly obsolescent, even at its introduction into Army service, the Krag was nonetheless a very sophisticated, accurate, powerful, and rapid to fire rifle. Krags in general, and American service rifles in particular, are posessed of such a fine bolt action that it simply has to be experienced to be believed. Loading for this weapon is through the somewhat ungainly side gate, which you open downward like an oven door, then cartridges are placed into it and closed. This was seen as a design improvement at adoption, but the Army seems to have changed its mind about the desireability of this feature midway. After encountering Mausers in the hands of Spanish forces in Cuba, the Army decided that stripper-clip fed rifles were the wave of the future, and began agitating for a new infantry rifle, despite the Krag's short tenure. They even went so far as to blame the Krag for the higher casualty rates Americans suffered at the Battle of San Juan (actually Kettle) Hill, which might likely have been attributed by more level heads to the fact that Americans were attacking uphill against entrenched, experienced Spanish troops with clear avenues of fire. Nevertheless, this agitation for a new arm resulted in the beloved 1903 Springfield Rifle. Krags still saw action in the Moro rebellion in the hands of the Phillipine Constabulary, even after being replaced in frontline service.
The 1903 Springfield might be the most loved of American service rifles by collectors and shooters, as well as being the introductory home of the .30-06 cartridge, probably the most popular sporting round to this day. The rifle itself is essentially a copy of the Mauser rifle the Army so coveted in Cuba, but with the 'improvements' of having a split bolt and a magazine disconnect switch. The disconnect is a feature which allows the rifle to be used as a single shot rifle while still having a full magazine of reserve shells for use in an emergency. In practice, it mostly was a nuisance as troops would forget to move it to the fire position before working the bolt, and face the enemy with a full magazine but empty chamber. Despite these shortcomings, and never being as widespread or ubiquitous as shooters seem to think, it was a good rifle, being accurate, reliable, powerful, and relatively compact.