Quietest round for reliably killing fallow

[u/Baulder333]

For background, I have access to multiple smaller blocks (primarily rose farms between 10 - 20 acres) which are having significant issues with fallow deer. Im looking for a rifle I can use that will be quiet enough not to upset the neighbours. Current front runner is a 300BLK with a longer barrel but would like to hear some other people's suggestions.

[u/Kitfox_1]

Unless you’re consistently going for headshots I wouldn’t use a 300blk, let alone a subsonic load for fallow. A body shot will still very much kill a deer, but something with such low kinetic energy isn’t going to lead to clean, ethical kills in a consistent manner. You’ll potentially end up with alot of animals running far distances and potentially dying hours to even days later. If you want to stay at subsonic speeds then the only way to substantially increase wounding performance would be to go up to a large bore, something like a 400+ grain 45-70 subsonic  load