I don't have any way of testing BBs against deer. That said, BBs can penetrate surprisingly well at 400-500fps because they are small, very hard and have a round nose profile.
There are too many variables to know what it's going to do to a deer at 100ft, but what it does to a steel can up close gives some idea of the potential. At 100ft it will have slowed down a good bit.
The ballistic tables I have aren't really set up to deal with steel BBs, but the best I can tell is that the BB might be going around 300fps at 100ft if they start out around 500fps. Maybe slower, but not much faster than that.
Of course, even if it does turn out to be harmless at that distance if it hits the haunches where the hide is probably pretty thick, a 33 yard shot with a smoothbore BB pistol is kind of a long poke. Normal competition distance for smoothbore BB guns is 5 yards, for comparison. Which means that where it hits is going to be pretty random and that introduces some potential for hitting a "soft" spot and causing injury.
Maybe set up some paper at 33 yards and see what kind of accuracy you are getting. If it looks like you can hold "minute of deer haunch" and you only take shots from the side (so you don't hit soft parts visible from behind) then maybe it's not a big deal.
There are too many variables to know what it's going to do to a deer at 100ft, but what it does to a steel can up close gives some idea of the potential. At 100ft it will have slowed down a good bit.
The ballistic tables I have aren't really set up to deal with steel BBs, but the best I can tell is that the BB might be going around 300fps at 100ft if they start out around 500fps. Maybe slower, but not much faster than that.
Of course, even if it does turn out to be harmless at that distance if it hits the haunches where the hide is probably pretty thick, a 33 yard shot with a smoothbore BB pistol is kind of a long poke. Normal competition distance for smoothbore BB guns is 5 yards, for comparison. Which means that where it hits is going to be pretty random and that introduces some potential for hitting a "soft" spot and causing injury.
Maybe set up some paper at 33 yards and see what kind of accuracy you are getting. If it looks like you can hold "minute of deer haunch" and you only take shots from the side (so you don't hit soft parts visible from behind) then maybe it's not a big deal.