General Ripley ordered Major John McNutt at the Leavenworth Arsenal to look into this matter of the Starr and Sharps carbines and cartridge interchangeability. On 1 September 1863 Ripley received McNutt's report: '...I have made some experiments with the (Starr) for the purpose of determining the suitableness of the Sharps Carbine Cartridge for it, and find that this cartridge is too short; the chamber of the Starr's Carbine being longer than that of the Sharps, and the consequence is the explosion of the cap does not always ignite the cartridge....I am satisfied from these experiments, that the Sharps Carbine Cartridge is not suitable for the Starr's Carbine....'
There were other problems with ammunition for the Starr as well. A report from 22 March, 1864 noted that some of the cartridges were 'too small (in diameter) for the piece, and this has been the great difficulty, when the carbine is slung, the cartridge, being much too small, slips so far down the Barrel, that the fire occasioned by the bursting of the cap, is not communicated thereto, and hence the failure to discharge.'
Interestingly even after these reports were issued it appears that improper ammunition continued to be used in the Starr. - John Gross, THE GUN REPORT, August, 2003.