Remove the barrel and then unscrew the magazine tube from the receiver.
If the mag tube is too tight to remove easily, use pliers or visegrips ONLY on the very last inch of the tube where the barrel screwed in. It's the only solid part on the tube and it won't bend or crush.
Follow instructions in owner's manual. If you don't have one, go to Mossberg's web site for information on how to get one.
If you are talking about the 50 caliber muzzle loader barrel for the Mossberg 12 gauge Shotgun model 500 or the Maverick 88 - you can't remove the breech plug. You have to clean the barrel like a flintlock. I just bought one from Mossberg's web page (arrived yesterday 12/21/08). It didn't come with any instructions. Fortunately, I found the manuals online at the following addresses: Muzzle Loader Barrel http://www.mossbergs.com/manuals/Muzzleloader.pdf 12 Gauge Shotgun Model 500 http://pdf.textfiles.com/manuals/FIREARMS/mossberg_500.pdf Good Luck
Best left to a gunsmith.
3 Shot only. No removable plug.
Take the cap off and point the gun doun and shake it and it should come out mine did
The average price of a Remington 870 Express Magnum pump 12 gauge shotgun "brand new" is about 300-450 dollars. I got mine used for $250
Yes, they did. My Dad owned one and it was an automatic 12 gauge capable of 5 shotgun if the plug was removed.
That depends on the shotgun and whether it as a "sporting plug" installed. A plug will limit the gun to three in the magazine. Without the plug, the gun may hold a few more. General, no more than five or so however magazne extensions can push that to eight or more.
My Mossberg maverick holds seven without the tube plug
The Westerm Field 550 looks like a Mossberg 500, so I would start there looking for a plug. A good gun shop might have one, a gunsmith could make you one, or gunpartscorp.com may have one on the shelf.
most pump shot guns have a cap on the tube below the barrel, this must be screwed off to remove the plug, be careful game laws limit the number of shells allowed
Wooden dowel