I recently purchased a Rack Grade Plus rifle from the CMP. It looks good overall and I was breaking it down for cleaning on Saturday and the gas tube will not come off. I took off the gas port screw and tried to gently tap it with a rubber mallet, but nothing. My question is how hard do I try and tap this thing to try and get it off, secondly if it will not come off, is it safe to fire, or will firing loosen it? I thought I read that the CMP fires the rifles it rebuilds, but not sure. Any help will be appreciated. Thank you .