Shotgun question
12-19-2005, 12:08 AM
#1
Thread Starter
Join Date: Jan 2005
Location: Texas
Posts: 27
Shotgun question
I recently bought a smith&wesson 12 gauge and it's not marked as far as the cylinder whether it is full modified or improved. What I am wanting to know is if there is a way to tell.I know they used to say if you could stick a particular coin in the end of the barrel it meant it was one or the other, but don't remember what coin that was. Can I get a little help here please?
12-19-2005, 07:58 AM
#3
Senior Member
Join Date: Jan 2004
Location:
Posts: 1,813
RE: Shotgun question
No matter how it's marked or what a dime will do, you won't know what you have untill you take it out and shoot at pieces of open news paper to see how it patterns! (at the ranges you will be shooting at while hunting) Use the ammo you want to hunt with, and check it yourself so you know for sure!
Drilling Man
Drilling Man
[/align]
12-19-2005, 11:52 AM
#6
Dominant Buck
Join Date: Feb 2005
Location: WC FL
Posts: 26,323
RE: Shotgun question
Subtract the reading form gauage size!
These are measured at a distance of 25 yards. The following chart can be used as a general guide.
[align=center]
Name
#%
Constriction
Cylinder Bore
40
.000
Skeet 1
50
.005
Improved Cylinder
50
.010
Skeet 2
55
.015
Modified
60
.020
Improved Modified
63
.025
Full
65
.030
Extra Full
68
.040
Super Full
70
.045
Turkey
70+
.045+[/align]
The above chart is based on using premium field loads with #8 shot. Generally the larger size of shot you use the less degree of choke is needed to get an equivalent size pattern. High velocity or magnum loads normally do not pattern as well as lighter loads. The same load by different ammunition manufacturers may not pattern the same. As you can see, there are many things that can cause a shotgun to shoot a different pattern with the same choke constriction. Most chokes will shoot a pattern reasonably close to the marked size, but the only way to be absolutely sure of what your gun is doing is to "pattern" it. Use the loads you plan to shoot and try different chokes to get the pattern you want.
These are measured at a distance of 25 yards. The following chart can be used as a general guide.
[align=center]
Name
#%
Constriction
Cylinder Bore
40
.000
Skeet 1
50
.005
Improved Cylinder
50
.010
Skeet 2
55
.015
Modified
60
.020
Improved Modified
63
.025
Full
65
.030
Extra Full
68
.040
Super Full
70
.045
Turkey
70+
.045+[/align]
The above chart is based on using premium field loads with #8 shot. Generally the larger size of shot you use the less degree of choke is needed to get an equivalent size pattern. High velocity or magnum loads normally do not pattern as well as lighter loads. The same load by different ammunition manufacturers may not pattern the same. As you can see, there are many things that can cause a shotgun to shoot a different pattern with the same choke constriction. Most chokes will shoot a pattern reasonably close to the marked size, but the only way to be absolutely sure of what your gun is doing is to "pattern" it. Use the loads you plan to shoot and try different chokes to get the pattern you want.
12-19-2005, 12:44 PM
#7
Join Date: Sep 2005
Location:
Posts: 510
RE: Shotgun question
One problem, Hog. The barrel diameters vary quite a bit among the manufacturers.
You are correct that the amount of choke constriction in a barrel is the difference between its bore diameter and the constriction at its muzzle. The best way to measure both is with a dial caliper as you showed. In a 12 gauge as an example, while standard bore diameter is supposed to be in the neighborhood of .729 to .730 inch, barrels from various makers can range anywhere from .720 to .735 inch, and those that have been backbored can be even larger. Assuming that the correct amount of constriction for, say, Full choke for the 12 gauge is .040 inch, it is easy to see how actual inside diameter at the muzzle can vary from .680 to .695 inch for that designation.
BNS, since you probably don't want to buy a caliper to measure one time, visit a gunsmith that works on shotguns and he can tell you the amount of constriction.
You are correct that the amount of choke constriction in a barrel is the difference between its bore diameter and the constriction at its muzzle. The best way to measure both is with a dial caliper as you showed. In a 12 gauge as an example, while standard bore diameter is supposed to be in the neighborhood of .729 to .730 inch, barrels from various makers can range anywhere from .720 to .735 inch, and those that have been backbored can be even larger. Assuming that the correct amount of constriction for, say, Full choke for the 12 gauge is .040 inch, it is easy to see how actual inside diameter at the muzzle can vary from .680 to .695 inch for that designation.
BNS, since you probably don't want to buy a caliper to measure one time, visit a gunsmith that works on shotguns and he can tell you the amount of constriction.
