Choke Tube Conversions Tables

Dear Technoid,

I have a Spanish shotgun (Lanber) and the chokes come marked with two, three and four dashes (++, +++, ++++). All the books and magazines I can get, talk about full, modified, and so on. What is the conversion from dots to the “American” measurements?

I’ve spent a lot of money on books looking for the solution but none has it.

Thanks a lot for your help.


Dear Carlos,

I really don’t know what Lanber uses for its choke markings. Everyone seems to do it differently. Beretta seems to come the closest in that they use a ++++ rating. + is Full, ++ is Improved Modified, +++ is Modified, ++++ is Improved Cylinder and no marks is true Cylinder, though I have also seen +++++ used for Cylinder.

Your normal chokes will run “approximately” as follows:

Full .035″ 70-75% pattern (in 30″ circle at 40 yards)
Modified .020″ 60% pattern
Improved Cylinder .010″ 50% pattern
Cylinder .000″ 40% pattern.
Improved Modified is somewhere in between Full and Modified.

Put another way, you “theoretically” should be able to produce pattern with the “bulk” of the charge in a 30″ circle with the following chokes at the following distances. If you don’t agree, blame it on Black’s “Wing and Clay”. That’s where I stole it from.

Bulk (whatever that means) of charge in 30″ circle at a distance

Full at approx 32 yards
Improved Modified at approx 30 yards
Modified at approx 28 yards
Improved Cylinder at 26 yards
Skeet 1 at approx 24 yards
Cylinder at approx 19 yards

I’m not sure that I agree with these numbers, especially the tight chokes ones, but it’s in print so it has to be true. Right?

I feel a bit more comfortable with Black’s “Pattern Density” table which shows 80% patterns for the following chokes at the following distances:

Full at approx 36 yrds
Improved Modified at approx 34 yards
Modified at approx 31 yards
Improved Cylinder at about 29 yards
Skeet 1 at about 24 yards
Cylinder bore at 20 yards.

Regardless of what your choke is marked, named or measured to be, you cannot be sure that it will throw a specific pattern. It will probably sort of throw that pattern, but it can vary a surprising amount with the particular shell and also with the particular barrel.

The only way to know exactly what your pattern is with a certain shell is to go out and pattern it. I keep saying this until I am blue in the face (well,I actually go from white to pink to green to blue), but it’s the truth. If you want t know for sure, you have to test. Otherwise, it’s just an act of faith. Like reading my stuff.

Best regards,

Bruce Buck
The Technoid writing for Shotgun Report, LLC
(Often in error, never in doubt.)

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