pretty sure 20 or 21 inches
Have a Model M-846 (Montgomery Ward) semi auto with 18 inch barrel.
AFAIK, there is no Winchester Model 90A. Is it a lever action, slide action, bot action, semi-auto or single shot? What caliber? What type and length of barrel?
No, it is a bolt action.
30 inches. A longer barrel gives you better accuracy.
Clean it. Try different ammunition. If neither works, find a gunsmith
Need serial number please.
Need more information - is this model a 9mm semi-auto carbine or pistol? Length of barrel and description of firearm is needed.
if you want it to be it is semi auto
Model 24 is a semi-auto 22.
16 inches, as required by the NFA.
Best left to a gunsmith.
Should be marked on the barrel