Shotgun Tube Having Gain Twist Rifling

Abstract

This invention relates to a shotgun tube, either an inserted/attached short section that replaces a conventional choice device, or one that forms an integral section of the shotgun barrel. It is designed to provide major advances in two performance features of shotguns: (1) It provides an extremely uniform expanded shot pattern at short ranges 10 to 20 feet and (2) it provides rotational stabilization for both rifled slugs and sabot encased sub-caliber projectiles that significantly improves accuracy at longer ranges.

What is claimed is: 
     
         1 . A shotgun barrel comprising: a screw-in device that mates to industry-standard threads for installation of standard chokes; said screw-in device having a nominal rifled length of about 4 inches; and said screw-in device having a slope of the rifling twist that starts at the chamber end of the unit with a low angular twist, typically near to zero degrees. 
     
     
         2 . A shotgun barrel according to  claim 1 , wherein the slope of the rifling twist increases continually toward the muzzle end of the barrel. 
     
     
         3 . A shotgun barrel according to  claim 1 , wherein the final rifling slope at the muzzle end of the barrel can be made to be any desired larger angle, of about 30 degrees. 
     
     
         4 . A shotgun barrel according to  claim 1 , wherein the groove depth of such gain twist rifling is about 0.010 inches. 
     
     
         5 . A shotgun barrel according to  claim 1 , wherein the groove width of such gain twist rifling is about 0.125 inches. 
     
     
         6 . A shotgun barrel according to  claim 1 , wherein the land width of such gain twist rifling is about 0.125 inches. 
     
     
         7 . A shotgun barrel according to  claim 1 , wherein the device can be secured to the muzzle end of a shotgun by soldering. 
     
     
         8 . A shotgun barrel according to  claim 1 , wherein the device can be secured to the muzzle end of a shotgun by clamping. 
     
     
         9 . A shotgun barrel according to  claim 1 , Wherein the grooves and lands of the gain twist rifling are designed to function properly with shotgun shells having a plastic shot cup. 
     
     
         10 . A shotgun barrel according to  claim 1 , wherein the grooves and lands of the gain twist rifling are designed to stabilize and improve long range accuracy of rifled slugs and saboted sub-caliber slugs.