Absolutely not. The Spencer required 4 drill movements to load the next round and recock the hammer. The rate of fire was similar to that achieved with Trapdoor Springfields whilst the magazine lasted, and when the magazine was empty it was outperformed by trapdoor conversions. Hence the flaw in the argument that Custer would have survived with Spencers; Spencers had less firepower than his BL carbines.
The M1 OTOH is a true self-loading rifle.
As we've discussed, Wilder's men were infantry, and deployed in the standard 2 rank, close order line. Their 4 regiments outnumbered Bate's 2 regiments by about 2:1, and yet the 37th Georgia actually broke the 17th Indiana with a bayonet charge (as we discussed
six months back).