Re: Is this ammo any good?
benny, first, welcome to The Firearms Forum.
If your Colt single shot derringer is chambered for WMR then shoot them. If it is not chambered for WMR then you will have a hard time putting the cartridge into the chamber so don't try to force it. It could be very dangerous. Shoot the .22 shorts or LR (again, if it will chamber).
NRA Endowment Member
Retired US Army
Retired Postal Worker