I agree with Two Flints... more info is needed to help properly identify this carbine.
I have trouble understanding the force that would be required to brake off part of the hammer spur, and not cause some other kind of damage to the gun. Especially to the internal parts of the lock. (Hammer spur could have been cut off, but that wont help operate a firearm that has to be manually cocked every time to fire it.)
VMI Cadet,
My original thought was the inside parts of the lock needed a good cleaning. Old grease and oil can dry out, becoming like varnish, causing parts not to work well together. Peened, and dented parts may also cause parts not to work well together, along with "not so correct" replacement parts.
This kind of cleaning can be done without disassembling the lock, however, the lock should be removed from the firearm to do this well.
This info may not help much at this time. More info and photos will, perhaps help.
My best,
Blair