I have a 16 ga SxS with IC and Mod fixed chokes.
Do those chokes have the same amount of constriction as a 16 ga made in countries othet than Germany. Or is the amount of choke restriction standardizes across geographies?

Thanks

Hi, German guns tend to be choked a bit tighter, but that's not cut in stone. The only real way to find out is to get a good bore gauge that you can measure the bore diameter, then what the choke diameter is. For example, if the bore diameter is .729 (12ga) and the diameter at the choke is .709 you have a constriction of .020 which would be Modified. Bore diameter will vary from gun to gun and if a O/U or SxS barrel to barrel. Choke will also vary like the bore diameter. So you really need to measure. I have guns (and choke tubes) that are marked Mod for instance, but really measure out at IC or IM depending. But, then to make sure what choke your throwing, you'll have to pattern the gun, which will take time and even then, the choke may vary from load to load. Just a matter of time and experimenting.

I can suggest a quality gauge, accurate and easy to use, not cheap, but it's a quality product:

http://www.theunloader.com/

Good Luck!

Greg

Many shotgun gunsmiths have special tools to measure bore diameter, and the amount of choke.

If you live near a Cabela's, they also have this tool in the Gun library section of the store.

Most will measure for you at no cost.

It may also be worth your while to pattern each barrel on a large piece of paper.

gold40

About ten years ago I reviewed a Merkel 2116 SxS with 20 and 16 gauge barrels. Both barrels were marked Improved Cylinder and Modified. The 16's bore was .007" overbore (.677 instead of the nominal .670") and the chokes measured .008" and .018" constriction.

That's it for a sample of one.

Bruce

In fact nominal size for a 16 gauge bore is .662" or 16.8mm. At .677 that bore was actually .015" oversize. At one point L C Smith bored their 16's to .650" or .012" under nominal. Later on they changed to the standard .662", with I presume a bit of manufacturing tolerance.

I'm predominately a Fox guy and factory bore for early Foxes were always under .662. They ran more around .658. I've owned several Merkel's over the years including 16 gauge and they ran under .662 also.

Many makers bored their barrels to other than nominal size for the gauge. Some were over while others were under. If you look in the proof house specs though you will see the nominal bore for the 16 is .662". This is based on the volume of a .662" diameter ball of pure lead will weigh 1 ounce or 16 to the pound. Matters not what any individual maker bores their barrels to, this is the nominal gauge size.

German guns, in general, seem more likely to be underbored than overbored, and more likely to be choked tighter than the typical constrictions for the given choke. But the only way to know for sure is to measure with a bore and choke gauge, as indicated above. The "drop-in" type choke gauges only give an accurate reading if the bore in question is standard diameter, or very close to it.

In some cases, the Germans are helpful in telling you how the gun is bored. I had a 20ga Sauer from the 1930's, A&F import, that was significantly overbored. In effect, a 19ga rather than a 20. But that was marked on the barrel flats, so I was not surprised when my bore gauge read close to .630 rather than the 20ga standard .615. And in the case of that gun--and others that are significantly overbored or underbored--the drop in choke gauge will give very misleading readings.

I have 3 Merkel SxS's in 28, 20, and 12 gauge. the bore dimentions are on the bottom of the barrel flats. The bore measurements are very close to standard published dimentions, if not slightly overbored. The chokes on all 3 guns are marked IC/MOD, and all measure .008" and .018". Odd indeed, but the big mystery to me is that all 3 throw beautiful IC/MOD patterns. I had the barrels measured at each purchase and found that the forcing cones in the choke area are somewhere around 6-8 inches long.
I have 2 Browning BSS-sidelocks in 12 & 20 gauge which measure conventionally, go figure.
Karl

df06, FWIIW, choke effect is controlled almost exclusively by constriction. Therefore, you really must be able to measure it reasonably accurately if you want to know what choke a barrel has. "Accurately" means within 0.003". And that basically means a caliper type tool. You must be able to measure bore diameter just before the constriction and the minimum constriction bore. Compare diameter constriction to the standard choke constrictions for a name for the choke.

Patterning. Can't recommend it unless you are really invested in knowing. Even with the very best shells and guns, there is so much variability from pattern to pattern that you must have 10 patterns per load and barrel combination. Further, you must run a statistical analysis on all 10. The first pattern might actually be an average pattern or it might be an outlier - no way to know.

Fortunately, if you are willing to shoot the patterns, digitally photo them, and run them through the Insights program, you can know for sure. It is a lot of work, but it is real.

DDA

There seem to be divergent opinions on the correct diameter of 16 gauge.

Boxall and Edmiston feels that it is .670"
http://www.boxallandedmiston.co.uk/shotg...ghtly-different

Wikipedia has it as .663"
https://en.wikipedia.org/wiki/Gauge_(bore_diameter)

Hallowell at .662"
http://www.hallowellco.com/bore_size_chart.htm

World Almanac and Book of Facts at .660"
https://www.unc.edu/~rowlett/units/scales/shotguns.html

International Hunter Education Association at .670"

forensicmed.co.uk at .665"

And so on.

If you look at the British proof house charts they list 16 gas as .662". "IF" you look up the weight of lead & calculate the diameter you will find that every gauge in the British system is "Just a Wee Bit Off". Calculations based on the weight of lead gives a very slightly larger diam than the charts. My "Assumption" is they took some given weight of pure lead, quite possibly a pound, formed it into a sphere & measured the diameter & calculated the rest. Perhaps in forming the sphere they compressed the lead just a bit & then used this size as the basis for the rest. By mathematical calculations .662" for the 16ga "Fits" in with all other gauge sizes from 1 to 172.28 in both English & German charts. Call it what you will, but if .662" is incorrect then ALL other charted gauge diameters are also incorrect.
One thing is for certain, Gunmakers have not always adhered to the standard. As noted for many years L C Smith bored 16 gauge barrels to "Their" standard of .650", others have also varied. None of this affects the true standard based on that 16 pure lead balls with a diameter which just fits the bore weigh 1 pound. Off size balls do not fit that standard.

Jack O'Connor's "Shotgun Book" (1965) gives 16ga bore diameters from the following manufacturers:
Winchester: .664
Browning: .665
Remington: .673.

I'd note that the same book shows a difference of .008 between standard 20ga bore diameters, and .005 between standard 12ga BD's.

Brophy's L.C. Smith book (with factory drawings) shows both Miller's .650 figure for the 16 as well as .652. Either case, a long ways from Remington's .673!.

Us guns are usually built to SAAMI specifications, and current SAAMI specs call for a bore diameter of 0.665" with a tolerance of 0.020", so a modern gun could have a bore of .665" to o.685" and still be within industry specs. Having said that, I have always heard that the 16 ga bore diameter was 0.662".

Once the diameter of a 1 pound lead ball (1 gauge) is known it is a simple matter to find the diameter of any gauge. You simply cube the 1 gauge size, divide by the gauge desired & then take the cube root of the result. One day some years back at work I was running a CNC milling machine on some airfoils which had cuts running for several hours each. I had to stay with the machine but had virtually nothing to to unless some unexpected event were to occur. I had copied off the chart of British proof gauge sizes. I had a programmable Casio Calculator. After putting in the program using a given size for 1 gauge I only had to enter a different gauge & it would give me the answer.
I very quickly discovered that using 1.669" for the base that all sizes did not fit, some came out too small. Stepping up to 1.6695 some sizes cam out too large. It proved out that to get a perfect match for the charts the 1 gauge ball had to be carried out to 6 decimal places. There was a very narrow range which would fit by rounding the end result to 3 decimal places. The figure I settled on was 1.6699285" for the 1 gauge ball.
As stated using this diameter fits all gauges listed in British, German & I believe Belgian charts from the proof houses from 1 gauge down to 172.28 gauge (.300 caliber).
These sizes have been accepted as standard since well back into the 1800's at least. Using .665" for the 16 would give .732" for the 12. It has always been listed as .729". Sizes for the common gauges are;
10=.775"
12=.729"
16=.662"
20=.615"
28=.550"
These sizes all have a perfect fit to "The Formula".
I also discovered that to obtain the "Tween" gauges as in 13/1 you average 12 & 13 then drop to three decimal places, the tween sizes are not rounded as are the primary gauges. On the larger gauges with two tween sizes as 8/1 & 8/2 you use third & two thirds & drop beyond three decimal places.
I have absolutely No Idea as to why SAAMI opted to change the size of the 16 but the .662" size has been nominal for "Well Over" a century.
As has been noted though individual makers have always bored guns to whatever they desired. The proof houses used the actual bore size to determine the proof charge, not the chambering. Thus if you had a gun chambered 12ga, but bored for brass shells with an enlarged bore which came up to 10 gauge diameter the gun would be proofed as a 10, not a 12.

Miller: the current SAAMI specs vary from the traditional sizes for the 12, 16, and 28 gauges, while the 10, 20, and .410 remain unchanged. The current sizes are 0.725" for the 12, 0.665" for the 16, and 0.545" for the 28, so two are smaller than the traditional sizes, and one is larger. I did not find an explanation for the variations.

If that tolerance works in both directions, then the bore diameter could be anywhere from .645-.685.

Tom;
Quite obviously SAAMI has not followed the traditional formula for gauges. Sort of makes the word Gauge of no effect as it would seem to be based on Nothing. To truly be a Gauge strongly implies a standard.

Larry: The tolerance is a one sided tolerance. There is a 0.020" on the plus side for all bore sizes, but no minus tolerance.

According to my (Rather Old) Machinery's Handbook they give the weight of lead @ 707.7 lbs per cubic foot. Using this figure a one lb ball would have a diameter of 1.670701 to six decimal places. This would make;
12 ga = .730"
16 ga = .663"
20 ga = .615"
28 ga = .550"
Thus two sizes show .001" larger than the charts, two remain unchanged. Some other gauges could grow by from .001"-.002" while many would stay the same, none would "Shrink" as the base for calculating (1 gauge) is larger by 1.416".
This is probably more than anyone wanted to know, but this is the Nitty Gritty in a Nutshell on gauge sizes.

In this video the gunsmith Jack Rowe seems to indicate that gauge tolerance works in both directions. 12 gauge could be anywhere between 0.710 and 0.751.

In part one of the video series he states that 0.008 (0.010 for 1954 requirements) is the most a bore can be enlarged and stay in proof. If it is bored out more than 0.008 above its proof dimension then it is out of proof and must be reproofed.

https://www.youtube.com/watch?v=PtvfSHr5TR4&list=PLB89EB25199C06E73&index=2

.751" is 11 gauge, 12/1 which began to be marked in 1887 in British proof is .740". In British proof when they were still marking by gauge rather than actual diameter a 12 marked barrel could be anything which would accept the .729" plug gage but would not accept a .740" one. From .740" up to .751" it would be marked 12/1. 13 gauge = .710" so 13/1 = .719. Any of these sizes could "& Were" chambered for 12 gauge shells. I even have one pre 1887 gun chambered for 12ga with bore marked as 14 (.693"). Prior to 1887 there were no "Tween" gauges so 14 could have been anywhere from accepting the .693" plug up to just not accepting a .710" one. In so far as I am aware of there were no legal requirements as to what a bore diameter had to be in relation to it's chambering. The gun was proofed according to it's actual bore diameter. My understanding was that when the bores were marked by Gauge, the gun was considered out of proof when it would accept the next larger gage than it was proofed to. fter the actual bore diameters began to be marked the .008" went into effect. Thus under the old system a gun having a .728" bore would have been proofed as a 13/1. As soon as it would accept a .729" gage it would have been Out of Proof. Under the new system it could go up to .736" & remain in proof.
The English gauge system listed all whole numbers from 1 through 50, 50 gauge being .453". Below this gauges were calculated for diameters in .010" steps from .450 down to .300" with the gauge carried to two decimal places. .450" =50.04 gauge with .300" = 172.28 gauge. A .410" bore incidentally is 67.49 gauge.

One of the curiosities of shotguns is how tolerant they are of bore size. Significantly smaller bore limits load "power," but larger bore only slightly limits reduced loads. A very sweet natured thing, this shotgun.

DDA