Choke tube markings are a series of lines, notches, letters, or numbers that help identify the size of a choke tube. The letters SP are usually written on the outside walls of the choke tube, and it can be confusing if you haven’t seen it before.
SP stands for Steel Proof. It 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.
What does SP mean on a choke tube?
SP means Steel Proof and these chokes are safe to use with steel pellets. 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.
More Choke Tube Markings
There are over 30 different choke tube markings used for choke identification. Below are the most common markings. Please click the links below to see what each choke tube marking means.
What chokes are safe to use with steel shot?
Choke tubes that are safe to use with steel shot meet the pressure requirements and hardness required for use with steel payloads. These chokes also have moderate diameters. Chokes designed for steel shot are marked with text stating it’s safe for use with steel.
Steel shot does not compact like lead or other malleable metals when it’s choked. This requires a steel choke tube to absorb forces that lead chokes aren’t capable of handling. Steel ammo should never be used in choke tubes designed for lead or any other shot not compatible with the steel shot tolerances.
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 will have the pellet type (i.e. steel, lead, hevishot, etc). Always follow the manufacturer’s guidelines to determine what shot types are safe to use with a choke.
Bottom Line: SP stands for Steel Proof
SP on a choke tube means that it can be used safely 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. Shotgun barrels and chokes not marked for steel shot should not be used with steel ammo. Start here if you need to find a choke tube that is compatible with steel shot.
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Related
- Complete Guide to Identifying Choke Tube Sizes
- Choke Tube Diameter and Constriction Table
- What do the numbers mean on a choke tube?
- Ultimate Guide to Shotgun Pellet Sizes
- What does 3 lines on a choke tube mean?
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