In January 1860 the Ordnance Office of the War Department reported 850 cases of arms had been shipped to Mount Vernon. Each case included twenty firearms and weighed about 300 pounds. 100 cases came from Watertown Arsenal; 750 came from the Springfield Armory. The total shipment weighed nearly 130 tons.

The 100 cases from Watertown contained 2000 Model 1841 Harpers Ferry rifles, cal .54. These were better known as "Mississippi rifles". There were already 32 of these weapons in inventory at Mount Vernon, so 2,032 were on hand when Alabama left the Union.

The shipment from Springfield included 9,280 Model 1842 percussion muskets, and 5,720 Model 1840 altered percussion muskets, both cal .69. Mount Vernon Arsenal had already converted 2,260 older model flintlocks to percussion (1855-57), the total on hand of this type in 1859 being 2,364. This brought the number of Model 1840 altered percussion muskets to 8,084. The report of both types of arms surrendered at Mount Vernon is actually 17,370.

Finally, there were on hand at Mount Vernon 33 Navy revolvers and 20 newer model U S rifled muskets. Total - 19,455 firearms.