There is no minimum caliber for deer hunting in Ontario.
Not all of Southern Ontario(That starts, in the North, at the French River. Think North Bay and South. No calibre restrictions up that way at any time or for any game. The MNR Hunting Season "catalogue" does not say anything of the kind.) has the daft calibre restrictions.
As mentioned, it's mostly Southwestern Ontario(pretty much West of Guelph/Wellington County.) that say .275 or less, but some municipalities around TO specify .270. Both by the cartridge name, not the bullet diameter(your instructor was wrong. The by-laws, which is what the whole thing is, say nothing about bullet diameter.). So a .270 Win is ok, but a .276 Pedersen(A 7mm x 51mm using a .284" bullet that you'll never find anyway.) is not. And some of 'em, but not all, say for small game only. It is rumoured that it started just after W.W. I to stop returning vets from using surplus Lee-Enfields etc. for hunting.
In any case, any .24, .25, .26 or .27 calibre will do as long as its name ends in a '0' or '5'. Your biggest issue will be finding a suitable rifle that'll do for both deer hunting and target shooting. Typical target/varmint rifles in deer suitable chamberings tend to be way too heavy to lug around deer hunting. Unless you hunt from a blind.
6.5mm is .264". Not .255". The .260 Rem uses a .264" bullet too. Math means nothing to cartridge names.
Not all of Southern Ontario(That starts, in the North, at the French River. Think North Bay and South. No calibre restrictions up that way at any time or for any game. The MNR Hunting Season "catalogue" does not say anything of the kind.) has the daft calibre restrictions.
As mentioned, it's mostly Southwestern Ontario(pretty much West of Guelph/Wellington County.) that say .275 or less, but some municipalities around TO specify .270. Both by the cartridge name, not the bullet diameter(your instructor was wrong. The by-laws, which is what the whole thing is, say nothing about bullet diameter.). So a .270 Win is ok, but a .276 Pedersen(A 7mm x 51mm using a .284" bullet that you'll never find anyway.) is not. And some of 'em, but not all, say for small game only. It is rumoured that it started just after W.W. I to stop returning vets from using surplus Lee-Enfields etc. for hunting.
In any case, any .24, .25, .26 or .27 calibre will do as long as its name ends in a '0' or '5'. Your biggest issue will be finding a suitable rifle that'll do for both deer hunting and target shooting. Typical target/varmint rifles in deer suitable chamberings tend to be way too heavy to lug around deer hunting. Unless you hunt from a blind.
6.5mm is .264". Not .255". The .260 Rem uses a .264" bullet too. Math means nothing to cartridge names.