Variances in chokes?

[Dean Romig]

You really can't measure a choke properly (or at least an older SXS choke) with a caliper. Choke constriction is not a static measurement but the amount of constriction as compared to the i.d. of the bore about 6" back from the muzzle. Even this description is a bit too simplified because an original Parker choke is more complex than a simple cone.

[J.B. Books]

They only way to really find out what any shotgun is choked is to carefully pattern it by shooting it and counting the holes in a 30" circle at 40 yards (many times).

Measurements are not meaningless but they don't tell you the full story. You could have a Parker that shoots full and full and the barrels might have 32 and 38 thousandeths of constriction.

Each barrel reacts diffently, each gun reacts differently. It might shoot extra full with 8's and modified with 6's. There are a lot of factors at play that cause this.

One the great things about Parker's is their chokes and ability of the tight chokes to really reach out and touch them. Parker put a great deal of effort into barrels, regulating them and shooting them to get desired performace. Choke perforamce is one the BIG reasons why I think a well worn Trojan is better than a lot of brand new anything.