I'm not 100% sure because I don't currently own one. I had one a long time ago and if memory serves me correct, I believe you do indeed push in the bolt charging handle once pulled back fully. I believe the cut out on the receiver (bolt travel channel)is rounded at the veryrear for this purpose. It will allow the bolt charging handle to be pushed in. Only one way to find out....Pull back the bolt all the way open and see if you can push in the handle (what you call a pin) to lock the bolt. Sorry I can't be more help it's been about 20 years since I held one.