choke question

[John McComb]

I have a PH model made in 1891 with twist barrels. It is 12 gauge, but mics at Right barrel = .739 and Left barrel = .730. My mic only drops in the barrel about 3/4 of an inch. Am I reading this wrong? The guy who sold it to me said it was IC and M.

Am I thinking in the wrong direction? Shouldn't the choke be smaller than .729 for 12 gauge?

John

[B. Dudley]

Your gun, like most Parkers of the period, likely has oversized bores. I have measured some 12g barrels to be as high as .750". In order to determine the chokes in your barrels, or any barrel, you NEED an actual bore gauge so that you can measure the bore diameter and also the amount of constriction at the muzzle. The constriction is the amount of choke, regardless of what the bore measures.

A drop in choke gauge or calipers on just the muzzle would only be accurate if the bore was actually .729".

[todd allen]

Ditto to what Brian said. Choke is determined by the difference between the measurement at the muzzle, and the back bore. Measures at least several inches back. Start with a bore guage, end with a pattern board. The gun will tell you what it is.

[John E. Williams]

This is why I've gone to patterning my shotguns the last several years. As a younger man, I was content to announce a gun's choke as whatever was roll marked on the barrel. Then, I began trying the measurement game and found bore and choke diameters varying pretty wildly from industry standard, as indicated by Brian and Todd in their posts. Eventually, patterning came to be my preferred way of actually knowing what I had. It was eye-opening to learn how easily I could manipulate pattern density by changing shell configurations, but the results of these changes are immediately obvious on the pattern board.

The little 16 ga. Parker bird gun I'm so fond of has odd bore and choke dimensions as I recall, but I can't remember the exact numbers sitting here at 3:30am. Regardless, it was averaging 58% (modified) patterns from the left barrel and 52% (*quarter choke) from the right at 40 yards with the load I was shooting. I recently switched to a different brand, dram equivalent, and wad type, so need to start the process all over and see how things have changed.


*Quarter choke, as I understand it and according to the chart I've adopted (from Jack O'Conner, I think), is of British origin and represents a choke having just a bit more constriction than our American improved cylinder. The chart goes something like this, according to notes I have scribbled here, and is calculated at forty yards:

Full Choke: 70% or above
Improved Modified: 65%
Modified: 55-60%
Skeet No. 2: 55-60%
Quarter Choke: 50%
Improved Cylinder: 45%
Skeet No. 1: 35-40%
Cylinder: 35-40%

[William Davis]

I finally broke down and bought a proper bore gauge. It gives a very good indication of how the barrel is choked, however how they pattern proves how they throw shot. Not all my guns that measure the same throw shot the same on paper. Look at point of impact too even more differences. And like John said the load is another factor.

May be if I ran more patterns they would match up or perhaps not. There is a limit to how much testing I am going to do but measuring and patterning is important if you want to know what the gun is going to deliver on targets or game. I know I have changed some of my loading as a result of patterning

William

[John McComb]

Thanks to all three of you guys. You have helped educate me on this issue. I knew if I put it on the forum I would get sound input. I really appreciate it.

John

[William Davis]

I am putting two Parkers in the car now for a round of Clays today. One is 20 G short and open other is 12 G long and tight. Will shoot the first half of the course with one 2nd half with the other. My shooting buddy the same pair of Parkers 20 & 12. Knowing how they throw will make a difference in how I take the shots. Short gun will probably go fast and try to break close to the trap. Long gun let the target develop and look for a break further away ( or the reverse if incoming) Other thing is I have gone to two shot sizes. 7 1/2 for the tight choked gun # 9 for the open gun.

At my age and eyesight need all the help I can get to hit targets. In the end choke is probably not all that important miss is a miss no matter how the gun is choked. Confidence is very important and knowing the gun makes a confident shot.

William

[John McComb]

Thanks William. Have a great day shooting.

John

[William Davis]

John

I should have added 90 % of what I know about Parker guns came from this forum. It's a wonderful resource

William

[GH-16]

Just to add my two cents worth to this discussion.

All of the above posters are spot-on with their explanation of choking. Parker themselves relied heavily on the patterning board for the purposes of determining the choking of a particular set of barrels.

I have several PGCA letters on the various Parkers I have owned. In a majority of these letters Parker in their records recorded choking as percentage of a certain size of pellet patterning in a specific size of circle at a specified yardage. As an example "left barrel patterns 180 pellets of #7 shot in a 30" circle at 40yards distance"

In my small sampling of letters. I have found this to be the normal means the factory used to determine choking. I do have a few letters where the chokes are stated as Full & Full, IC-Mod etc. My conclusion based on the letters I have seen is that Parker spent a lot of time at the patterning board to get their chokes just right for any particular gun.

Bottom line is the only way to really determine how your gun is choked is to spend time at the patterning board.