What does 4 lines mean on a choke tube?

Choke tube markings are a series of lines, notches, letters, or numbers that help identify the size of a choke tube. Choke tubes with 4 lines usually appear on the top of the choke tube and it can be confusing if you haven’t seen it before.

4 lines means IMPROVED CYLINDER. Lines indicate the size or constriction of the choke tube. A Benelli choke tube with 4 lines (IIII) is an Improved Cylinder choke. Beretta shotguns that use Mobil chokes will also show 4 lines to indicate Improved Cylinder.

Browning choke tube markings are slightly different, and 4 lines means Skeet Lead or Light Modified Steel. The line markings on a choke tube can be found etched into the top edge of the choke.

What does 4 lines on a choke tube mean?

4 lines on a choke tube indicate the size or constriction of the choke tube. A Benelli choke tube with 4 lines (IIII) is an improved cylinder choke. Beretta shotguns that use Mobil chokes will also show 4 lines to indicate improved cylinder.

Browning choke tube markings are slightly different, and 4 lines means Skeet Lead or Light Modified Steel. The line markings on a choke tube can be found etched into the top edge of the choke.

Improved Cylinder diameters differ based on shotgun brand and choke system. Below is a chart showing the diameter of improved cylinder chokes by brand.

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 edge of the top of the choke (opposite the threads) and are deep gouges that can’t be easily removed. Choke tube lines appear as I, II, III, IIII, and V.

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.

Browning Choke Tube Markings

Benelli Choke Tube Markings

Beretta Choke Tube Markings

One line on a choke tube is always the tightest constriction for that brand of choke. It denotes a Full choke. 4 lines on a choke tube range between Improved Cylinder and Skeet and are slightly more open than chokes with one line.

2 lines are universally Improved 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: 4 Lines Means Improved Cylinder

4 lines on a choke tube means that the choke is Improved Cylinder in size. An Improved Cylinder choke tube is an open choke just tighter than Skeet or Cylinder.

Improved Cylinder choke tubes with 4 lines work best for close ranges of up to 30 yards for ducks, geese, dove, and upland game. Lines on a choke tube can be found etched into the top of the choke tube.

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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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