you really should be using a good quenching oil such as brownells tough quench, since it has a much higher flash point than regular oils, i.e. motor oil. there is also less chance of the work piece warping after dipping it into tough quench.the reciever should be completely disassembled. the reciever should have a light coat of oil on it and then heat applied, with the flame in continous motion until the steel starts to colour. it should then be dipped in the quenching oil or have oil wiped on with a shop swab. allow to sit for about 24 hours, then carefully degrease and apply a good gun oil.this is how i've done it a fair few times and the finnish is very nice. i don't know that it's as good as hot blue or colour case hardening,but it's btter than cold blue. if you mess up , just remove the gun oil and buff off the finnish with a felt buffing wheel or a fine grit oxide paper and start again. good luck