You use the choke tube which is appropriate to the use of the shotgun.
Choke tubes are short sections of tube which screws into the muzzle end of the shotgun barrel. Different tubes hve different amounts of constriction (full, modified, improved, cylinder bore, etc). The tighter the constriction, the more the shot column is kept together and thus the more dense the shot column. This keeps the column together longer as it flies down range and thus will put more pellets into the target. Tighter shot column also means that the pattern doesn't spread out as much and thus it's harder to hit a given target.
They usually use a modified (medium) choke on the 870, unless it has choke tubes.
If it has choke tubes, yes. If it is fixed choke, no. I called Browning about mine and that was the answer they gave me.
Browning made choke tubes.
For the Stoeger side-by-side shotgun, your best bet would be to use any of the standard Winchester choke tubes. They should fit well for you shotgun.
They identify which chokes you have in without having to use a choke tool. different companies have different markings but in general the fewer marks, the more constricted the choke (1 mark=full choke).
Modified describes a choke. Invector is a system of choke tubes.
I am a gun dealer in Asheboro, NC (Franks gun and pawn). Yes, the Baikal choke tubes will fit. This gun is made by Baikal for Remington. It used to be imported under the EAA name. You can also get tubes at Colonial choke tubes.
You can use a wire instead of the starter to test the tubes .. I did it, it works !
Tubes that constrict the column of shotgun pellets as they exit the barrel
Only with cylinder and improved cylinder choke tubes.
Try Mid West Gun Works.
On the choke tubes. It is marked by lines on the front edge of the choke. The more lines the more open the choke. 1 line is a full and goes from there. If it doesn't have tubes, on the inside of the receiver near the bbls.