Just measured a Browning “Lightning Sporting Clays Edition” with their “backbored” barrel and Invector Plus system.
Top barrel 0.738″, bottom 0.739″ (advertised 0.742″)
Skeet no constriction (measured 0.740″)
I.C. 0.003″ constriction
Mod 0.011″ constriction
I.M. 0.017″ constriction
In my gun these chokes are consistently a full choke designation looser than marked.
Yup, that’s the way Browning does it. It was the same with the early short Invectors too. Those all had much more open constrictions than normal. More open patterns too.
I keep saying this and I can’t emphasize it enough- you have to pattern the gun. You definitely can’t trust the choke designation stamped on the barrel or choke. Just miking the choke often doesn’t tell the whole story either, though it is closer.
Since you say that you have done the work and your choke/shell combination patterns true to the constriction (the usual case, but not always) why not just relabel that -.002″” as Cylinder bore, the .003″ as skeet, the .011″ as IC, the .017″ as Lt Mod or Mod and send off to Briley for something that measures around .703″ to give you about .035″ for a Full. Briley will send you chokes of an exact measurement if you deal with them directly and ask for a specific ID rather than a named choke designation. If you buy them off the shelf at the gun store, you had better bring a barrel mike with you.
There is nothing at all wrong with Invector Plus chokes that a little patterning and relabeling won’t cure. You can’t trust ANY gun/choke combination to pattern as labeled with every shell, so you have to test no matter what brand you own. Browning is just a bit (a lot?) further off then everyone else, but the chokes still pattern well based on their constriction size, if not their label.
I keep my screw chokes in a little compartmentalized plastic fishing lure box. Each compartment is labeled as to the true constriction of the choke that lives in that compartment. The particular choke is always returned to the same compartment. This saves me putting on my reading glasses when I have to change chokes. Works great until I spill the whole box into the dirt- which I do about once a year. If you have one of those Dremel tool vibrating markers, you could buff out the choke designation name stamped on the choke and scribe in the actual dimension.
Shotgun Report’s Technoid
(Often in error, never in doubt.)