[ExSoldier]

What brand of .22 is the most deadly?

No such thing. There are only deadly men.

[Beagle8U]

"What brand of .22 is the most deadly?"

It might be a scary sounding 22 Automatic ?

I own one that my grandfather bought new.

Winchester 1903 22 cal. Automatic. ( yes, they are labeled as automatic)

They were the first commercial 22 semi- auto but the normal 22 LR rimfire of the time were black powder and would foul the action after a few shots.

So Winchester made the 22 automatic chambers and cartriges slightly larger in dia. so they wouldn't fit in the regular 22 cal. and used smokeless powder.

I believe the thinking was the higher chamber pressures of the smokeless powder might damage the older black powder 22's.