Croppy Boy said:
I have read all the posts on jug choking and have decided to do my 12 bore Pedersoli Mortimer. Around here you rarely get a shot at 25 yds and will probably go for full choke.
Unfortunately, there is no one this side of the duck pond who knows about jug choking let alone doing it so I've decided to do it myself. I bought honers from Brownells (medium and fine), I have an inside calipers, a 1/4" bore guide and a drill. I intend taking out 0.03" for about 4" starting 2" from the muzzle.
Does anyone have any advice to give me regarding these specs. or is it all just a bad idea?
Not a bad idea at all...I had a .62cal Flint smoothbore Jug Choked and it works fantastic.
You first have to ensure you have good barrel wall thickness to allow fo a .030" oversize expansion chamber to be honed into it.
Essentially a Jug Choke is an "expansion chamber" that's created using a cylinder hone in the bore, with 1.5" tapers on either side of it.
One gunsmith explained that it is approximately 6 " long, stopping 1/2" from the muzzle, consisting of three parts:
A 1.5" gradually expanding taper
A 3" expansion chamber
A 1.5" gradually reducing taper, stopping a 1/2" from the muzzle.
Imagine you're traveling down the barrel from the breech towards the muzzle:
You encounter the 1.5" expanding taper starting about 6.5" in from the muzzle;
Then a .030" expansion chamber is enlarged for about 3";
Then the 1.5" reverse taper works back down to the original cylinder bore diameter a 1/2" before muzzle exit.
The expansion chamber itself is honed about .025"-.030" larger than cylinder bore dimensions for a full choke effect.
The shot charge expands as it passes through this chamber causing the outer layers to start slowing down some, while the center continues moving forward at full speed.
Then as the expansion chamber tapers back down to normal cylinder bore dimension just before muzzle exit, the outer layers of shot are forced to regain speed and merge back into the trailing part of the shot column, and as the gunsmith put it, makes the shot "squirt" out like the ML was a high pressure fire hose".
All these dynamics somehow create a situation where the shot column is influenced in a way as if it had gone through an actual mechanical choke restriction...and it works.
That's the best way I can explain it based upon how one gunsmith explained it to me.
A different gunsmith actually did mine and his Jug Choke work seems shorter than 6"...more like 4"...but works on the same principle and definitely works well...here is his contact info if you'd like to pursue it further. (his Email address is his HAM operator call sign).
Lowell Tennyson
209 E Lotte St.
Blue Grass, Iowa 52726, USA
563-381-3711
[email protected]
Hope this helps...
