Round
Not very familiar with the .270 as a round but here's my $.02...
Try a lighter skinned round such as a fail safe or maybe a frangible.
Try a lighter round (weight). Small caliber + heavier round means smaller wound channel but deeper penetration. You need to create a larger wound channel.
Lighter skinned + .270 caliber should be enough power for proper penetration yet provide a wider WC to allow blood to exit. Maybe double penetration (entry & exit channel) + smaller caliber is insufficient to allow blood to exit to make trailing easier.
Or just keep your tracking dog healthy!
Your mileage may vary.