Choke tube markings are a series of lines, notches, letters, or numbers that help identify the size of a choke tube. The letters IM are usually written on the outside walls of the choke tube, and it can be confusing if you haven’t seen it before.
IM stands for IMPROVED MODIFIED. It designates the choke tube constriction size and in this case IM is between Modified and Light Full with regards to tightness. It measures 0.695” in diameter on fixed choke 12 gauges.
Improved Modified chokes are used for waterfowl hunting and upland game. They help provide tight patterns at medium to long ranges between 30 and 50 yards. If you see “IM” or “I. MOD” written on a choke tube, you can be sure it’s an Improved Modified choke.
What does IM mean on a choke tube?
Choke tube letters designate the diameter of a choke tube and IM is included in these designations. IM stands for Improved Modified Choke and is near the middle ground of all choke diameters.
Some chokes can be labeled as “IMP MOD” and this means Improved Modified as well. This designation is brand specific and isn’t related to the standard naming scheme. Improved Modified will be listed as IM, IMP MOD, or Improved Modified. IM chokes should not be confused with light modified or modified choke tubes.
What is the diameter of Improved Modified chokes?
Improved Modified diameters differ based on shotgun brand and choke system. Below is a chart showing the diameter of IM chokes by brand.
| Type | IM Diameter (inch) |
| Beretta/Benelli Mobil | 0.696 |
| Benelli Crio | 0.697 |
| Beretta Optima Plus | 0.702 |
| Benelli Super Sport | 0.697 |
| Beretta Optima | 0.702 |
| Browning Invector | 0.697 |
| Invector Plus | 0.710 |
| Remington | 0.697 |
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 are IM choke tubes used for?
IM choke tubes pattern tighter at medium to long ranges. They are ideal for shots on waterfowl, dove, and upland game out to 50 yards. They work best with medium sized steel and lead shot. They can also be used safely with most turkey loads.
Improved Modified chokes are one of the most popular choke sizes for hunting, and are usually included when you purchase a new shotgun. The all-around performance of improved modified chokes between 30 and 50 yards is worth the investment.
Are IM choke tubes open chokes?
Improved Modified choke tubes are not open chokes and are near the middle ground of all choke sizes available. IM chokes are tighter than modified, but more open than light full. They are considered a medium range choke tube and they are designed for hunting ducks and geese over decoys. 50 yards is usually the max distance for steel shot with these chokes.
Improved Modified chokes excel with most ammo and shot types due to its forgiving diameter that doesn’t constrict the shot column too much, which can result in blown out patterns. It can also be used with TSS shot which delivers devastating downrange patterns for waterfowl and turkeys.
Bottom Line: IM Means Improved Modified
IM stands for Improved Modified Choke. It will be written on the side of the choke tube. Improved Modified chokes perform in between that of Modified and Light Full chokes.
Improved Modified chokes are great for providing dense patterns for waterfowl and upland game at medium to long ranges. It’s also one of the preferred chokes for turkey hunting.
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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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