doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Choke Measurements

Well said, Stan.

Going back to the initial post: If you have a 12ga marked .729 and you measure the bore at .735, it's still in proof. It does show evidence of having been honed, but that's not necessarily a bad thing. Honing the bore but leaving the choke alone is one way of increasing constriction. Harder to put choke back in than to take it out, but that's one way to do it.

Also good points above about patterns varying from one brand of ammo to another. However . . . before you pattern, you need to count pellets. I've examined 1 oz loads of US 6's--supposed to be 225/oz--that range in count from high 190's to about 250. That's obviously going to have an impact on pattern density/percentage.

My favorites on here is when someone buys a new gun and before they ever lay their hands on it, want to know who can open up the chokes because the readings given were not what they wanted.
All of the "smart" replies were to pattern the gun with the shell you are going to use. The other replies were in my opinion the "dumb" ones that gave a persons name to do the work.

Right now my favorite sporting clays gun is a 1907 L.C. Smith hammer gun. When I bought the barrels they were from a Grade 1 hammerless and were 30" long. I asked the seller what the chokes were and he stated he did not have a way to measure them (yeah sure). I bought the barrels anyway and found out from our records ledgers that the gun was shipped with 32" barrels. There is still .014 constriction 1/2" from the muzzle in both barrels.
These barrels shoot very well and I have shot some incomers at approximately 45+ yards, and are also good at 20 yards.

As Stan stated also, gun fit is most important. I've read that most of the best shooters prefer full choke guns.

And beyond measurements, and beyond patterns on paper, it still comes down to how the gun performs in your hands.
I have an AyA number 2 in 20 gauge, .007 and 021 chokes, which I think produces perfect upland game patterns, I just can't put the pattern where it needs to be.
In contrast, I have an Italian hammer double 12 by Armi San Marco, a very humble gun, choked .015 and. 025, which I think a tad tight, but the gun works for me. I think I am a little slower mounting the gun, and maybe more consistant in the mount.
Ultimately, measurements and patterns are only a hint towards performance in practical terms. Just my 2 cents worth.

Tamid is wanting to generate some meta-data vis-a-vis bore/choke measurements. I can only ask again - why bother?
What Stan says is the wholly practical aspect of the measurements and he says still a guess. Of course. What else can be said?

have another day
Dr.WtS

"IF" one does want to figure the % of the choke dia of the bore dia then choke/bore is not the proper way. As diameters are proportionate to the square of their diameters then it should be choke�/bore� or (choke/bore)�.
Thus a .693" choke is not 95% of a .729" bore but rather only 90%. Thus while it takes .036" to reduce the .729" bore by 10% with a 20ga a .615" bore it would only take .032" constriction to give the same 10% reduction.
While totally agreeing the actual pattern is the final answer knowing the constriction is certainly a good thing to know prior to purchasing a gun.
A gun with this amount of "Full" choke constriction s no more apt to give a desirable pattern for skeet o woodcock than is an IC choke apt to give a desirable pattern or handicap trap or pass shooting waterfowl. It's far better to buy what you want to begin with than start modifying all these old irreplaceable guns.

There are many new guns back bored larger than .729. Many Parker hammerguns came with .740+ bores [ I have one ]. My Parker 10ga has larger bores than todays 10ga guns. The only way to know how much choke you have is to measure the bore and construction at the muzzle. TW had it right for numbers. When buying a used gun I like to know the construction as a starting point even if it doesn't pattern exactly as you think it should. As far as I know 1/4, 1/2, and 3/4 would be IC, Mod, and IM, or .015, .020, and .025.

And that is my point. I have never had the luxury of test firing and patterning a gun prior to purchase so I have to have some type of constriction measurement so I at least have a starting point.

Cheers,
David

The exact amount of constriction has always varied some by maker. Many makers however followed the system of .040" or 1mm being full choke. 1/4, 1/2 & 3/4 were then fractions of that number IE .010", .020" & .030" respectfully. I/C was with these makers around .006". Many american makers though the shooter didn't truly know what they wanted & bored I/C barrels to 1/4 choke but marked them I/C anyway. In true terminology I/C is a lesser choke than is 1/4 & is just what its nae implies, a very slightly choked "Improved" cylinder. This was considered a big improvement over a true cylinder in soft shot & card/felt wad days.

It was so much easier back when; courtesy of Daryl

That's a good point. Belgian Brownings are one example of guns that, generally speaking, have more constriction for a given choke designation than did other contemporary makers. A chart in Jack O'Connor's old classic "The Shotgun Book" shows that Browning's 12ga mod constriction was .024, compared to .018 for Remington and .016 for Winchester. That's a pretty fair spread. And if you put your bore and choke gauge into a Superposed or A-5, you'll find it has more constriction than what you'd expect, given the choke marking.