I think you're right in this case. It appears to be the outline of the GI grip safety and not a case of hammer bite. That second picture posted is more in line with hammer bite. I think it's due to a rough grip safety as well.As an NRA Instructor I would say the mark on the OP's web is the mark of a GI grip safety. Why his hand reacts the way it does is beyond me but that is definitely the outline of a GI grip safety. I've seen it happen to many new shooters. If the grip safety has sharp square corners it will eat your hand. The reason it has sharp corners is because the maker didn't want to spend time or money radiusing those corners. Colt especially LOVES sharp square corners. People have complained for decades but Colt doesn't listen to anyone. Grinding a small radius on those corners will help - it will still be painful but not as bad and it won't leave the mark. This is precisely the reason upswept beavertails were developed back in the day. With one you can shoot a 1911 all day in comfort. Try to shoot a 1911 with a beavertail and see. You can get a "drop in" that will stop the pain but will be kind of ugly - or you can shell out a couple hundred pesos and have a nice one fiitted to your frame.