I would think this is a key point of the original poster.

HeymSR20, mentions a .22 Hornet. I remember a Kiwi writing an article on buying a .22 Hornet Savage as his new deer rifle in NZ. Probably NZ does not have the same laws as Scotland though. I have shot dozens and dozens of deer with a .22 Magnum and since one or two failures, the .222 Remington. Most of these were farmed deer though. In the wild I would be reluctant to use the .222 unless I only had it in hand. Brain shots are what I use. Broadside heart shots are also said to work well as well, only done one, above the heart for a "halal" shooting with a .22 Magnum. Decided after that fisaco, to use the .222 Rem next time for a "not instant" kill. If I bothered ever again. Was not impressed ie this attempting shots to "not kill instantly" so the heart is still beating for prayer time ...

A broadside shot to hit the heart should work well. Or a bullet designed to blow up inside the lungs. But the problem is if bone, dense muscle is hit and a fragile bullet blows up with only surface wounds. Then a long chase might be needed.

Back to the .22 Hornet. Would make a dandy roof rifle choice IMO even if it isn't legal for deer.

I have a Martini Henry cut back 'sporting rifle' in .222 Rimmed. Haven't used it much. Still need to get it scoped. BTW any tips on mounts being sold, still looking.

From another thread: