take the barrel off the gun and look for the threads if you have no threads you will need to have it threaded at a gun smith, if there are threads it may take a little work to find out what choke brand will fit.
the gun you showed a pic of HAS removable chokes. if there is a choke already in there you won't be able to feel the threads cuz the choke is using them. you will only be able to feel the threads after the choke is removed. MAKE SURE THE GUN IS UNLOADED, remove bbl and find someone with a choke tube wrench (shouldn't be to hard). if that tube is realy rusted in there (last person never lubed it) they could be real tough to get out and you could do some damage with a quarter, (as you have no leverage). try soaking it a bit in some liquid wrench or some type of penetrating oil before trying to remove again. with the standard M.B. chokes a dime will fit inside a modified 12 gauge choke but not a full or extra full. look at the inside of the muzzle end of the bbl, if you see 2 notches opposite each other, that a quarter will fit into, then you have a choke already in there. you really need to contact mossberg and get a owners manual (free) and a choke wrench app 10$ and learn how to assemble/dissaemble and care for your gun. these newer chokes sit flush with the end of the bbl's, the older ones had a knurled ring that sat app 1/8" external to the bbl and you could remove/install by hand. worst case scenario is that choke may never come out and you will learn to live with it by patterning your loads, which you should do anyway or getting a new bbl.
Here's your owner's manual in PDF:
http://pdf.textfiles.com/manuals/FIREARMS/mossberg_500.pdf
Lots of good stuff to know!
You can get a wrench for under $5 and other choke tubes here:
http://www.cheaperthandirt.com/46110-1.html
the gun you showed a pic of HAS removable chokes. if there is a choke already in there you won't be able to feel the threads cuz the choke is using them. you will only be able to feel the threads after the choke is removed. MAKE SURE THE GUN IS UNLOADED, remove bbl and find someone with a choke tube wrench (shouldn't be to hard). if that tube is realy rusted in there (last person never lubed it) they could be real tough to get out and you could do some damage with a quarter, (as you have no leverage). try soaking it a bit in some liquid wrench or some type of penetrating oil before trying to remove again. with the standard M.B. chokes a dime will fit inside a modified 12 gauge choke but not a full or extra full. look at the inside of the muzzle end of the bbl, if you see 2 notches opposite each other, that a quarter will fit into, then you have a choke already in there. you really need to contact mossberg and get a owners manual (free) and a choke wrench app 10$ and learn how to assemble/dissaemble and care for your gun. these newer chokes sit flush with the end of the bbl's, the older ones had a knurled ring that sat app 1/8" external to the bbl and you could remove/install by hand. worst case scenario is that choke may never come out and you will learn to live with it by patterning your loads, which you should do anyway or getting a new bbl.
Thank you for your infos and in one word, I'm an idiot... lol I try to fit new choke tube that I bought from Dicks yesterday and It wasn't fitting. So Im like Why is not fitting....And I woke up next morning, realized "Ah there was a choke tube already inside!" lol hahaha
