AR15 pistol in 300 black out

[Markhpb01]

Has anyone used a 300 blackout pistol for deer hunting? We are getting My son ready for the TX deer season and my pistols fit my 6 yr old son really well. Farthest shot he would take would be around 75 yds. I’m really more curious about the lethality of the blackout round on whitetail in the neighborhood of 175 lbs. seated in the stand he is more than capable of making a good shot so I’m looking for answers regarding placement. Thanks.