It is a shame about the southern Ontario .275 rule. I have found through experimentation with subsonic lightweight(115 gr) cast loads for my .308, how effective and clean killing a flat nosed 30 cal is at 1000 or so fps. Damage akin to a HP .22LR, and certainly no more than even a rn fmj 9mm(35 cal).
Then I got to thinking about how quiet and effective they were. But 308 is too large a case for this for anything other than a few grouse loads per year. A bolt action 7.62x39 takes care of all that. A small enough case that low volume of fast burning flake powder(I like Red Dot) burns fairly clean and consistent. The available bullet moulds, especially from places like N.O.E., really have an amazing variety of bullet styles.
Not much but change loads and re-sight to have an effective deer or coyote rifle either...