Regardless of whether or not an anti-beartrap is fitted, it is sound practice to hold the barrel/underlever down with one hand whilst feeding the pellet in with the other. The best technique is to hold the butt into the groin while you're loading it. That makes it stable.
TD once told about an experiment that the magazine guys did with a pigs trotter and a '77 I believe. Gruesome stuff.

It's part of most clubs safety policy that one hand should always be on the barrel/underlever.

Mick

No pigs were harmed during the writing of this....