Choke tube markings are a series of lines, notches, letters, or numbers that help identify the size of a choke tube. Choke tubes with 6 notches usually appear on the top of the choke tube and it can be confusing if you haven’t seen it before.
6 notches on a choke tube means a CYLINDER CHOKE. Choke tube notches or lines represent the constriction level of the choke. For a choke with 6 notches, the diameter is fully open, providing an even shot pattern with minimal constriction. This is ideal for close-range shooting and can be effective for hunting in tight cover or when birds are flying in close proximity.
What does 6 notches on a choke tube mean?
6 notches, lines, or stars on a choke tube mean the diameter of the choke is Cylinder. For Benelli and Beretta shotguns using the Mobil choke system, 6 lines means Cylinder. For Browning shotguns with Invector series chokes, Cylinder will have no markings.
Cylinder diameters differ based on shotgun brand and choke system. Below is a chart showing the diameter of cylinder chokes by brand.
| Type | Cylinder Diameter (inch) |
| Beretta/Benelli Mobil | 0.726 |
| Benelli Crio | 0.727 |
| Beretta Optima Plus | 0.732 |
| Benelli Super Sport | 0.727 |
| Beretta Optima | 0.732 |
| Browning Invector | 0.727 |
| Invector Plus | 0.740 |
| Remington | 0.727 |
Why are lines used on choke tubes?
Choke tube lines are notches that are gouged into the choke to identify the choke size without needing to remove it from the shotgun. Lines on choke tubes feature 5 standard choke sizes including Full, Improved Modified, Modified, Improved Cylinder, and Cylinder.
The lines on most chokes are marked at the top edge of the choke (furthest away from the barrel) and are deep gouges that can’t be easily removed. Choke tube lines appear as I, II, III, IIII, and V.
Chokes with notches or lines on them are most common with flush factory chokes. Because these chokes sit even with the barrel when installed, it would be impossible to identify choke size without lines or markings other than having to remove the choke entirely.
Additionally, writing on a choke tube can wear off with time, especially with heavy use. The choke diameter may not be clearly legible or even visible on some older chokes. Markings such as lines and notches cannot be easily removed, and will remain for the life of the choke.
What if a choke tube doesn’t have any lines?
Some aftermarket choke tubes with customized choke sizes do not have choke lines. The diameter of the choke is typically etched onto the side of the choke instead.
Subsequently, most factory choke tubes do have choke tube lines which adhere to the manufacturers marking guidelines. Popular Browning, Benelli, and Beretta choke tube markings are listed below. Consult the manufacturers website if you are unsure of what choke markings mean.
In some cases, a choke tube will have no identifiable features. Please consult a reputable gunsmith to determine sizing and choke system compatibility before using.
Browning Choke Tube Markings and Lines
I – Full Lead or Steel
II – Modified Lead, Improved Modified Steel
III – Improved Cylinder Lead, Modified Steel
IIII – Skeet Lead, Light Modified Steel
None – Cylinder Lead, ImprovedCylinder Steel
Benelli Choke Tube Markings and Lines
I – Full
II – Improved Modified
III – Modified
IIII – Improved Cylinder
V or VI– Cylinder
Beretta Choke Tube Markings and Lines
I – Full
II – Improved Modified
III – Modified
IIII – Improved Cylinder
V or VI – Cylinder
One line on a choke tube is always the tightest constriction for that brand of choke. It denotes a full choke. 2 lines on a choke tube range between Light Full and Improved Modified and are slightly more open than chokes with one line.
3 lines are universally modified chokes with steel shot and four lines are improved cylinder or skeet. Some manufacturers use dots instead on lines, but the premise remains the same.
Bottom Line: 6 Notches is Cylinder Choke
6 notches on a choke tube means that the choke is Cylinder in size for some brands. A cylinder choke tube is the most open diameter of choke and similar in size to the bore diameter of the shotgun itself.
Cylinder choke tubes with 6 notches work best at close ranges up to 20 yards for sporting clays and upland game hunting. Lines on a choke tube can be found etched into the top of the choke tube.
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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