RFDS PC12 aircraft practice turn-backs at Adelaide in Australia. So do the RAAF in their PC9's. However, inquiries to the manufacturer of these aircraft (Pilatus) reveal that under no conditions is the turn-back a part of the certification or the endorsement process.
What has killed people in the past is the practicing of turnbacks - not the real thing. So the more you practice a turn back, the higher the chances of one day killing yourself and taking some unfortunate soul with you - either in the air or among the houses on the ground.
There have been six pilots killed in military aircraft in Australia practicing turnbacks. I should add that two were killed in a Vampire turn back following a turbine failure. The fields ahead were clear and the chances of a successful straight ahead forced landing were high. But the crew had been brought up on turn back practice and gave it a go this time. It wasn't their day. They smashed in on close base leg and that was the end of them.
The others were killed when the practice turn backs went horribly wrong. Both aircraft spun in during the turn back manoeuvre. Two were alive after the aircraft hit but were burnt to death because they were too dazed to escape.
Forget "practicing" turn backs. It is simply not worth the risk assumed.