Don't feel too bad about passing this combo up. To see what I'm talking about, fire a few rounds off with a cap and ball revolver holding the gun in the same position and distance from your face that this gun with the butt stock attached would hold the gun, BUT, BE SURE TO WEAR EYE PROTECTION!!!!!!In fact, don't even try it...There is good reason not many people used these.
Colt, always the entrepreneur, when designing a New Model Army (NMA) revolver starting around 1858, having prototypes of a lightened 1848 Dragoon which did not work sufficiently, settled upon using the 1851 Navy frame for the future 1860 Army .44 revolver. The US Army was also interested in a cavalry carbine in .44, so Colt tried 4 different type designs of his proposed revolver shoulder stock and patented his Type 3 stock. When the ACW was underway about late 1861-early 1862, the US Army found that the shoulder stock on the 1860 Army for mounted cavalry troops was unwieldy compared to having at least a pair of revolvers either on the soldier, or in saddle pommel holsters as was previously used with the Old Model Army (OMA) 1848 Dragoon revolvers.
According to Charles W. Pate
The Colt Model 1860 Army Revolver (2018) pp. 20-21, US Army records show that from June 1858 to June 1860, before the Colt NMA was produced, 546 shoulder stocks were delivered to the US Army, all for the OMA.
If you compare the number of shoulder stocks contracted by the US Army compared to the number of Colt Dragoons in their inventory, it is a miniscule amount.
When Colt introduced the 1860 Army and the shoulder stock (which were considerably dimensionally different insofar as the stock yoke dimensions from the Dragoon), the stock was most probably written off as far as US Army purchases, but there were some indicated by various extant surviving stocks. I have nothing to back up that statement.
To get back to your post, my ASM 1860 Army with shoulder stock, when assembled, has a 15" LOP, which is at least an inch longer than any currently produced long gun. Imagine your cheek on the comb of that stock. I understand your concerns about eye safety, chain fires, et al.
As long as the revolver has nipples that fit the caps one is using, a chain fire is virtually a non-existent possibility. Don't place your off hand forward of the trigger guard, and you are good to go.
Been there and done that.
Regards,
Jim