Gentlemen,
I hope that you may find the following interesting, and informative.
Although this manual pertains primarily to the M1903, The following is  contained in the appendix:
The following modifications of the Revised Infantry Drill Regulations are prescribed for troops armed with the U.S. Magazine rifle, M1898.
54. 1st. to prevent accidents the magazine and chamber are to be opened and examined, when details, detachments, and other bodies of troops are first formed, and again just before they are dismissed.  In the commands the word CHAMBER refers to both magazine and chamber.
3rd.  the cut off is to be kept turned down except when using the magazine.
Lastly, and I found this to be very interesting to me as a new comer to the ranks of the M1898 rifle shooters.
146.  The rifle can be used as a magazine rifle by turning the CUT OFF up.  the use of the rifle as a magazine rifle is, however to be regarded as exceptional.

1stazmilitia

It's important to remember that the Krag was replacing the single-shot Trapdoor.  One of the things that put the nail in the coffin is the Spaniards rate of fire, while US troops were firing single shot!  The Mausers were fired quicker, AND reloaded quicker than the Krag... and significantly quick than the Trapdoors that MOST of the troops in Cuba were using!