Choke / barrel's inner dimensions

fcompton · January 19, 2001, 11:53 PM

Maybe someone can explain this…. I have been using a Ruger Red-label over and under 12 gauge for trap for over one year and have traded it in for a 1992 (like new) browning Citori trap with a double and single barrel. (got tired of taking it on the cheek)

What confuse’s me is the chokes. On the Ruger the id of the choke tubes are as follows: Imp=.735, Mod=.730 and Full=.720. Of the new Browning which has a fixed bore (no choke tubes) the over / under has the top barrel as .680 and the bottom as .695.

How can a trap gun have both barrels choked smaller than a full choke as on the Ruger? And why would the single barrel on the Browning have the smaller of the two chokes which is .680
Are the id’s of chokes supposed to be the same size or are they different for each type of gun and different yet for guns without tubes?
Thanks for your help
Fred

Dave McC · January 20, 2001, 06:04 AM

Each maker has its own idea of proper bbl and choke dimensions. The important part of how tight each choke is is the difference between the bore diameter and the choke diameter. Some folks call .001 inch one Point Of Constriction, and full runs up to 40 POC, Modified around 30 POC, etc.

PJR · January 20, 2001, 08:02 AM

There are few things more confusing than shotgun chokes. The standard interior dimension of a 12 gauge is .729" but I own guns that range from .723 up to .740 (due to backboring). The actual amount of choke constriction depends on the interior dimension of the barrel. The only way to determine the actual constriction is with a inside bore gauge.

Regardless, choke performance is the key and the only way to determine how your gun is shooting is to pattern it with the shells you intend to use. Shell selection can affect pattern as well. I currently have a gun that according to the chokes is IC and modified. However, on the patterning board it's closer to improved mod and full with my usual hunting loads.

DML · January 20, 2001, 03:45 PM

Dave McC and PJR are correct. Choke is simply the amount of constriction. For example, Remington IC barrels have about .008" constriction at the muzzle, but they don't hold their tolerences very close. I have barrels in the shop right now that measure .720/.728 and .738/.746 yet they are all marked IC.

There are many factors that determine what kind of patterns a barrel may shoot. Shot size, type of wads, shot cup, powder, etc., etc. A barrel that has .020" constriction may be called Modified, but may throw anything from an Improved Cylinder to Full choke patterns. Only patterning the barrel with various brands of shells and shot sizes will tell you for sure.

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January 19, 2001, 11:53 PM	#1
fcompton Junior Member Join Date: January 19, 2001 Location: Jackson NJ Posts: 14	Maybe someone can explain this…. I have been using a Ruger Red-label over and under 12 gauge for trap for over one year and have traded it in for a 1992 (like new) browning Citori trap with a double and single barrel. (got tired of taking it on the cheek) What confuse’s me is the chokes. On the Ruger the id of the choke tubes are as follows: Imp=.735, Mod=.730 and Full=.720. Of the new Browning which has a fixed bore (no choke tubes) the over / under has the top barrel as .680 and the bottom as .695. How can a trap gun have both barrels choked smaller than a full choke as on the Ruger? And why would the single barrel on the Browning have the smaller of the two chokes which is .680 Are the id’s of chokes supposed to be the same size or are they different for each type of gun and different yet for guns without tubes? Thanks for your help Fred

January 20, 2001, 06:04 AM	#2
Dave McC Staff In Memoriam Join Date: October 13, 1999 Location: Columbia, Md, USA Posts: 8,811	Each maker has its own idea of proper bbl and choke dimensions. The important part of how tight each choke is is the difference between the bore diameter and the choke diameter. Some folks call .001 inch one Point Of Constriction, and full runs up to 40 POC, Modified around 30 POC, etc.

January 20, 2001, 08:02 AM	#3
PJR Senior Member Join Date: May 31, 2000 Posts: 1,127	There are few things more confusing than shotgun chokes. The standard interior dimension of a 12 gauge is .729" but I own guns that range from .723 up to .740 (due to backboring). The actual amount of choke constriction depends on the interior dimension of the barrel. The only way to determine the actual constriction is with a inside bore gauge. Regardless, choke performance is the key and the only way to determine how your gun is shooting is to pattern it with the shells you intend to use. Shell selection can affect pattern as well. I currently have a gun that according to the chokes is IC and modified. However, on the patterning board it's closer to improved mod and full with my usual hunting loads.

January 20, 2001, 03:45 PM	#4
DML Senior Member Join Date: November 24, 2000 Location: Aridzona Posts: 257	Dave McC and PJR are correct. Choke is simply the amount of constriction. For example, Remington IC barrels have about .008" constriction at the muzzle, but they don't hold their tolerences very close. I have barrels in the shop right now that measure .720/.728 and .738/.746 yet they are all marked IC. There are many factors that determine what kind of patterns a barrel may shoot. Shot size, type of wads, shot cup, powder, etc., etc. A barrel that has .020" constriction may be called Modified, but may throw anything from an Improved Cylinder to Full choke patterns. Only patterning the barrel with various brands of shells and shot sizes will tell you for sure.