Pittsburghunter

Instead of leaving the breech plug loose in your son's MDM just take a wrench and every ten shots or so twist is forward and back to make sure it is staying free and not seizing. If you feel it not wanting to move, that is the time to pull it and clean it, then re-apply anti sieze and put it back in.

That's not all that bad an idea with any inline. It gives you a chance after say 20-25 shots to field break the gun down, and give the barrel a better then swabbing cleaning. (and to cool down in many cases) I do this even when changing projectiles for shooting if I have fired a lot of shots through the rifle. That way I know I am starting very clean again.

The trouble with leaving the breech plug real loose is you're just asking for blow back through the breech which will only produce more fowling. I never really tighten the plug down, but I don't leave it loose. I don't know how else to explain it....