Volunteer Commando Mk 45.
We have a Manchester Arms/Volunteer Arms Commando Mark 45 in the shop that does not fire every time, leaving only a light strike on the primers. Where we can find a new firing pin and spring? Failing that, how best can these be removed for inspection and identification? We checked Numrich and they weren't stocking most parts for the Commandos.
Since nothing turned up in the Standard Catalog of Firearms we entered "Manchester Arms Commando" into a search engine and found information about Commando Arms/Volunteer Enterprises and their firearms at VolunteerCommando.webs.com/ manuals. These guns are "Chicago Typewriter" (Thompson .45 submachine gun) look alikes with a straight magazine instead of the 50-round drum. These are not clones of the original Thompson and are not fully automatic. If it were, this response to your inquiry would end here.
Since that is not the case, these are semi-automatics with a fierce trigger pull. They were initially produced by Commando, previously named Volunteer Arms, as the Mark III. In production from 1969 to 1976, the model was changed to Mark 45 after the Volunteer Arms name ceased to exist. You will very likely have to reach beyond Numrich for replacements. Your best bet is a copy of the Brownells Gun Parts Source List for out-of-production firearms.