You may have noticed SP marked on your choke tube and are wondering what it means. SP is a marking on some Benelli and Beretta Mobil chokes that means it’s compatible with steel shot.
SP stands for “Steel Proof” and designates that the choke tube is safe for steel shot. Some chokes are only designed for lead shot, so it’s important to examine the choke tube closely to make sure SP is written on it if you intend to use steel ammo.
Related – Looking for a new choke tube? Check out the top picks here.
SP Choke Tubes
Choke tubes with SP written on them are designed to handle the higher pressures of hard steel shot. Steel shot compresses less than lead shot, and a choke tube needs to be able to withstand these tolerances.
SP choke tubes will have the letters “SP” written on the side of the choke tube. It’s important to identify if a choke tube is compatible with steel shot before using it. Some lead choke tubes are not compatible with steel shot.
What if a choke tube has no markings?
If you don’t see SP written on the choke tube it may not be compatible with steel shot. Most factory Benelli and Beretta Mobil chokes will have either SP written on them or “lead shot only”.
Aftermarket choke tubes such as Patternmaster and Carlson’s are designed to be used with many different shot types, so they won’t have SP written on them, but instead with have the pellet type (i.e. steel, lead, hevishot, etc).
Mobil Choke Tube Markings
I – Full
II – Improved Modified
III – Modified
IIII – Improved Cylinder
V – Cylinder
Beretta/Benelli Mobil Choke Sizes (12 gauge)
Below are the common diameters of Mobil chokes for each choke type.
Improved Skeet (0.716)
Improved Cylinder (0.711)
Light Modified (0.706)
Improved Modified (0.696)
Light Full (0.691)
Xtra Full (0.681)
SP on a choke tube means that it can be used with steel shot. Beretta and Benelli Mobil choke tubes commonly are marked with SP which stands for “steel proof”.
SP choke tubes are constructed to withstand higher tolerances due to increased pressure of hard steel shot over softer lead pellets.