When asking about ammo,it helps to include the headstamp.
My guess would be that it is a .45 Colt shotshell,they were loaded in wooden capsules at least into the 1920s.
Military training rounds in rifle calibers were loaded with wooden bullets
a least untill WW2,I have never encountered any headstamped later than
WW2.
I can never recall seeing any pistol caliber ammo with wooden bullets other than the above mentioned shotshells.
WC