doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Chokes by label--full,mod, etc vs constriction

Looking at 12 gauge constrictions from this Ithaca chart; full (4) = .036", IM (3) = .027", Mod (2) = .018", IC (1) = .009" & Cyl = 0.000 (0) Note the numbers in parenthesis are the old Ithaca numerical choke markings.

Doesn't look that much different to Browning Specs to me & again the IC choke is equal to British & Continental � choke. There, these chokes would be called Full, 3/4, �, � & Cyl. Note that 3/4 of .036 = .027, � of .036 = .018 & � of .036 = .009 which matches exactly with the listed choke diameters. IC other than in the US generally meant from 003" to .006" of constriction. It was meant to improve the performance of a cylinder bore without materially reducing its spread, just help even out the pattern. It was a great improvement with the old card & felt wadding of the day.

I've often referred to the Briley charts.
https://www.briley.com/c-447-choke-charts.aspx

The 12 ga. Briley chart is my go-to reference. I memorized the .005" steps many years ago. It has worked well for me, and since i shoot CompNChoke tubes in most of my screw-choked guns, it matches their designations, too.

If Briley's chart is right for .410, what would they call the "Full" choke tube for my FAIR Iside that has .034" ?

SRH

Stan, .034 in 410 is about what my friend's Perazzi had for the tightest barrel. I have a Beschi NID with similar constriction.

I havent patterned mine enough to know if it shoots tighter than an more common. 020 full choke.

I haven't either, but I will, as I have these that came with the gun.

C - -.006"
IC - +.003"
M - +.012"
IM - +.023"
F - +.034"

I did shoot the +.034", once the other day, with a 3/4 oz. WW load, on the plate just to see how tight it was, and it is truly tight. Next outing with it I will try it against the +.023" for comparison. One thing interesting I did see............. the -.006" (Briley calls it a diffusion choke) threw a beautiful first barrel quail pattern out to 20 yards.

SRH

I've always preferred thinking in terms of the numerical constriction, rather than an arbitrary name whose specific definition is not always the same everywhere.

Properly, choke designations are indicators of pattern performance (percentage of pellet strikes in a 30 inch circle at 40 yards), not a specific constriction. Even using that standard there is considerable variation in how specific loads perform in a given choke designation in any barrel.

I have always spec'ed choke work by supplying ammunition of my choice and specifying pattern percentage to be achieved. This requires care and testing by the 'smith doing the work. Much easier, of course, to specify constriction, which relieves the 'smith of the tedium of cutting, checking, cutting, checking, etc. He need only produce the constriction desired and he's done.

Hard to find a 'smith these days who will bore a gun to the pattern specs provided, rather than just cut to a given constriction.

My friends and I do that too, James. When we shoot sporting clays together and someone asks one of them "what they shot on that bird", they will answer a "5", or a "10", etc.

"Course, I joke with them a lot because I shoot two fixed "20s" in my MX 8. Sometimes we will look at a bird, or a pair, that will be really close and I will mumble "Hope I've got enough choke for that". Other times they will discuss a presentation and one will say "A "0" will kill that". I will reply "Maybe, but I'm sure a "20" will.

SRH