Adjustable choke inner diameters

[mr.ridout]

I bought a Higgins Choke Master. It is a perforated noisemaker tube with an adjustable choke (like a Poly Choke) on the end. I've never seen one like it.

It has six detent settings. They are listed below with each measured inner diameter.

Cylinder and Slug- .751"
Improved Cylinder- .748"
Modified- .744"
Improved Modified- .740"
Full- .737"
Extra Full- .733"

If 12 gauge barrels are nominally .730" then how could this choke be doing anything. It doesn't look extremely worn.

Could the inside of the collar be worn away enough to make this much difference

Does the shot spread out in the compensator tube and the diameters of the chokes are adjusted for that?

Is it likely that the diameters are correct?

 

[Virginian]

It is highly likely the chokes perform as per the label with lead shot, and possibly even tighter with plastic shot collars. The enlarged section functions similar to a jug choke requiring less constriction after it.

 

[PapaG]

There is an expansion diameter before you get to the choke fingers. Shot expands as it leaves the bore and is snugged back down in the choke. Cutts open ends are over an inch where they accept the shot after it leaves the barrel. My Poly choke is the same but not quite as big.

 

[mr.ridout]

Thanks, that makes sense. Just wanted to be sure. I did read where chokes are made based on measurement of the pattern at a given distance, and not really by any mathematical formula.

 

[PapaG]

Thanks, that makes sense. Just wanted to be sure. I did read where chokes are made based on measurement of the pattern at a given distance, and not really by any mathematical formula.

That is the only true way, patterning.