Wow. I went over to Pomona Airgun's site and apparently they're "working on Marauder Magazine conversions". So they'll be charging people for MY idea. Cool...
Can't help on thread gauge other than it should be 18 threads per inch and OD = 15.8750 mm.What happened with reg.? did it dump tank or did you have a slow leak? or blow burst disc? I was getting an occasional leak at valve(air coming out barrel and found if I cocked it, it went away.
Tony - Mine looks like yours and says 16unf. Still on the gun tho.