Jug Choke = Back Boring

[roundball]

Finally found an article which better explains Jug[url] Choking...in[/url] modern shotguns it's called 'back boring'...the physics & results are the same...
[url] http://www.gunnersden.com/index.htm.shotgun-back-boring.html[/url]

 

[paulvallandigham]

Actually, Jug Choking and Back boring are NOT the same. With Back boring, the diameter of the barrel begins at chamber diameter, and then gradually is reduced to choke size at the muzzle.Today, it is not uncommon for a backbore barrel in 12 guage to actually start out at 10 gauge dimensions at the chamber, and taper down to 12 gauge where the choke is located behind the muzzle.

As you know from having your barrel jug choked, a " wide chamber " is actually cut into the barrel several inches behind the muzzle, with a slope or angle leading into the chamber, and another slope or angle leading out of the chamber. The width of the chamber determines the amount of choke that is given to a column of shot.

In today's firearms, the equivalent to a Jug Choke, would be the compensating chambers sometimes cut into pistol barrels, although they work entirely different. With the modern pistol barrel, the compensating chamber allows gases to first expand into the chamber, and then vent out of holes either drilled or cut in the wall of the chamber between the bore and the outside, directing the gase out and up to push down on the barrel to " compensate " for recoil forces that want to make the muzzle rise. Since you are shooting a single projectile, there is no reason to mechanically push it back into the bore before it exits the muzzle.

 

[Eric Krewson]

I may be wrong but I think Colerain turkey barrels are back bored instead of jug choked.

 

[MikeC]

I may be wrong but I think Colerain turkey barrels are back bored instead of jug choked.

I believe your correct. For sure they are not jug choked.

 

[roundball]

I may be wrong but I think Colerain turkey barrels are back bored instead of jug choked.

I believe your correct. For sure they are not jug choked.

Just to be clear, my point was not that "back boring" and "jug choking" were precisely the same...the point simply was that the physics are the same that produce the increased choke effect...ie: the bore being larger prior to muzzle exit gets a greater choke effect from the existing degree of choke that was already at the muzzle...mentions the effects of a shorter shot string, etc

For example, my Remington 1187 Trap gun is backbored and using a normal Imp. Cyl. screw in choke produces a full choke pattern...thought it was a good article worth sharing as some folks (I think) don't have a good understanding of HOW a jug choke works, and this puts in print the physics & results from an enlarged chamber prior to muzzle exit...happens to be in a backbore configuration but the results pattern output is the same principle.