choke constriction depth?

[stinky]

W/my 12 gauge I learned my lesson, I patterned it and behold, it wasn't a IC it was a tight full choke...no wonder I either missed or birds disintegrated. So, on that gun I bored it out and came to a IC/mod type of deal and instantly went from a slug to an expert shotgunner.

So, I pattern the kids 20 gauge single-shot and it is also a tight full choke. Now, my question, how long is the constriction that makes up the choke? I have a Remington choke tube to go by and it is only 1.5" long. The choke constriction dimensions are available pretty much everywhere, but not the length of them. What I want to do is ream it out, shoot it, ream it and go from there. How deep do I need to ream? Or, if I just ream the muzzle, 1" deep, to the spec, for a certain choke, will that work?

[Bayrat]

There are no hard rules as to how much, but the longer you can make the taper, usually the more even the pattern will be.

The longer the taper, the longer the time span the pellets have to "re-arrange" themselves, thus producing less back pressure at the choke area. That means fewer flyers (distorted pellets) are produced.

With short tapered chokes, the pellets are forced together more quicker, raising pressure, which damages pellets, which tends to produce more flyers as they pass through the choke area.

Short chokes not only throw more flyers, but often will not have as even a pellet distribution within the pattern as a long taper chokes for the same pattern percentage. They tend to throw clumps of shot leaving holes in the pattern.

And short taper chokes can do strange things with certain types of wads. My friends short tapered choked 12 gauge field gun throws perfectly hour glass shaped patterns with Remington SST target wads. The recoverd wads from his gun were bent almost in half sideways instead of opened evenly like happens with other design wads. He switched to using Winchester AA's and gets round patterns.

With my longer taper chokes, the Remington SST patterns are slightly oval.

Also, taper length is not the only thing that can affect how well chokes pattern. I find my best patterns are with long taper chokes that have a short straight section just before the muzzle opening. The manufacture of the chokes says they do that to give the shot column a chance to stabilize before exiting the barrel. Seems to work, because other long taper chokes I have from that same company don't pattern quite as evenly.

And don't forget the forcing cone.
Short forcing cones can be worse on patterns than many chokes are because the forcing cone is back where the pressures are greater. One of the reasons many target guns have lengthened the forcing cones, and others even increased the bore diameter by back-boring is to further reduce that pressure created pellet damage.

Another benifit of lengthing the forcing cone and backboring the barrel, or like Mossberg did with the 835 eliminate the forcing cone all togther by backboring it to a 10 ga, allows for less choke constriction needed to get the same pattern precentage as a short forcing coned, non backbored, short tapered choke gun would. All that removing and lengthing of constrictions in the barrel contributes to fewer flyers produced, and more even pellet distribution.

Also, what patterns a gun throws can depend alot on the ammo used. Pellet size, how hard the pellets are, what coating if any the pellets have, and what speeds they go at, what chamber pressures that shell produces, all affect patterns. Just making changes in which wads, powder, type pellets and speed can make changes in patterns equal to a couple of choke size differances.

And you thought it was going to be simple, huh ? :D

Bayrat.

[Greybeard]

Bayrat. Back about 1970, I owned an Ithaca trap gun that someone put a polychoke on. Barrel length before the Poly was 31.5". Played with the idea of having the barrel cut to 30" and rechoked. Fortunately there was a nice solid rib support at 30". Off to the best gunsmith around and we discussed the project. He had been following Olympic shotguns and brought up the Russian's short cone choked guns with which they did very well. I ok'd the project. He cut it off and cut out a short cone choke bit by bit, patterning the shotgun after each gradual cut. He came up with an outstanding pattern and stopped right there. I ended up with a great trap gun with a barrel that was exactly at 30" that appeared exactly as if it had come from the Ithaca factory. All I can say is that some short choked shotguns can have great patterns. What is the better generality, long or short chokes? I don't know. Greybeard/

[MOGC]

Make the parallel section too long then regardless of the constriction it will most probably throw a cylinder pattern.

[Bayrat]

GB,

That's why I used, "no hard rules" and "usually" in the first line.

Choke work can seem like alchemy at times. :D

Also, same model guns, same chokes, same ammo, all off the same production runs and it's not uncommon to see noticable differances at the pattern board.

Being able to get custom choke work done is the best way to make the most of a shotgun. I do all my own gun fitting and barrel/choke honing/polishing, and then pattern each gun, with each choke for that gun. Then pattern all my reload recipes that will be use in that gun/choke combo. Makes for ALOT of drawing circles and hole counting, but otherwise, it just guess work. Hey, why not, there's not much on TV.:D

Interesting about the Russians.

Many years ago I read the Russians also developed specially choked barrels for skeet that taper, then a short, straight section of larger ID, then the last part of the choked area just before the muzzle narrows down again. The idea was to get the shot column to constrict, then expand, then constrict again to "bounce" the pattern open more than a straight cylinder barrel is capable of producing. Don't know if they used them in competition.

Bayrat.