Yes, it is legal. However, it is illegal to hunt migratory birds with a shotgun that holds more than 3 shells (2 in magazine, 1 in chamber). That is why many "bird guns" come already plugged. All self defense shotguns have the plug removed. I believe in most states you can hunt deer and other game with unplugged shotguns.
Gun is restricted to 3 rounds by design. It has no mag plug, that is where the gas system is.
You can't, not without machining expertise, or gunsmithing
A shotgun typically stores 5 rounds in its magazine. In some countries, when hunting certain types of game, you are only allowed 3 rounds in your magazine. The "plug" therfore goes into the magazine and takes up the space that two rounds would occupy., reducing the shotgun's magazine capacity be 2 and making it legal. Thus removing the plug restores the shotgun's capacity for a full magazine.
Take the cap off and point the gun doun and shake it and it should come out mine did
Best left to a trained gunsmith.
To remove the plug from a Winchester Ranger shotgun, first ensure the shotgun is unloaded and pointed in a safe direction. Then, locate the plug inside the magazine tube, usually accessible by unscrewing the end cap or the magazine cap. Once the cap is removed, you can slide the plug out from the magazine tube. Reassemble the shotgun by securely replacing the cap.
To remove the plug from an Ithaca Model 51 autoloader shotgun, first ensure the firearm is unloaded and pointed in a safe direction. Disassemble the shotgun by removing the barrel and then locate the plug, which is housed in the magazine tube. Use a flathead screwdriver to unscrew the retaining screw if present, then carefully pull the plug out of the magazine tube. Reassemble the shotgun once the plug is removed, ensuring all parts are secure.
Wooden dowel
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.
no
Best left to a gunsmith
While hunting, yes. Otherwise, no.