choke and jug choke confuse me

[foresterdj]

Have been a shotgun shooter for over 50 years. Have patterned many conventional shotguns and well know and observe that tighter levels of choke yield denser patterns at a given distance, or equivalently dense patterns at a farther distance. Of course most choke descriptions are described as percentages of pellets within a 30" circle, because the number of pellets to begin with varies by load (ounces) and by shot size. Pellet size being chosen for penetration (individual pellet energy) for the game being shot at the range you expect to shoot them. Many variables, much anecdotal information available, conventional "wisdom" and mere speculation. I am sure this thread will repeat much of this as 101 different absolute (and some contradictory) facts are expressed.

None-the-less, here is my question. How in the heck does choke actually work?

For years I just figured that by making the muzzle smaller, it just took the shot a little longer to spread back out, and given how fast they are moving forward, relative to the outward spread speed of the cloud of shot, that a specific shot pattern density would happen farther away.  So, using 12 ga. as an example, assuming a bore of .729" straight cylinder (no choke constriction) and this table.



Shot column leaves a .729 muzzle, 40% of the shot in circle. Squeeze it down to .709" (modified constriction of .020") and now 60% are in the circle. And many examples can be made. A 20 ga. cylinder of .615 has 40% at 40 yards, constricted down to .601" (a 20 ga. modified restriction of .014") does 60% at this distance.

Now we consider a jug choke, as used in a ML, where the internal bore is widened out for a ways, but then squeezed back down, but only to the bore it originally was. So there must be more to how a choke works than simply the exiting diameter.

Then when I consider that the ML shooter has (between some minimum and maximum amount) a basically infinite range of load ounces available (vs the conventional loads commercially available for breach loading shotguns), and when I consider that pattern density that matters is the actual number of pellets in the target area (not a percentage), is it not just as easy (or easier even) for the ML shotgun shooter to affect actual shot pattern density by changing load exiting his straight bored gun and just forget all about this jug choking idea?

For disclosure, I have never shot a ML shotgun, but hope to build one winter '24 - '25 (hopefully with the pending Kibler fowler kit).

[axelp]

Here are my thoughts and not at all scientific. I too have been a shotgun shooter for a long time, but am just bored mountain boy who liked to hunt and still do.

With a choked barrel the shot is compressed together as it moves into the smaller space so the trajectory of the shot "squeezes" inward into the shot column itself and as it leaves the muzzle,  it just takes longer for it to change direction naturally and spread out.

In the case of a jugged choked barrel. The shot column moves forward thru the muzzle and then hits the enlarged space, expands, and THEN compresses back into itself-- again after leaving the jugged area, So a similar "squeeze" effect occurs.

Of course it only takes three licks to get to the center of a tootsie pop too, so perhaps the world will never know the real scientific reason. All I know is, my full choked shotgun gets birds further away from me than my cylinder bore does.

Ken

[Daryl]

Ken covered it. It's simple physics.

If there is TOO much constriction, the shot is badly damaged and shoots larger patterns than less tight chokes due to "fliers".
Too much constriction with steel shot and the choke is damaged. This happened to many older shotguns when the steel shot laws
came into effect. The barrel steel wasn't hard or tough enough for the shot that didn't  'compress' well.  What usually happened with
single barrel guns, is the choke constriction would open up (muzzle expand) to something just larger inside, than a modified choke. Some
muzzles split, while double barreled guns had the joining ribs split or detach from the barrels as the muzzles expanded.
Bismuth shot is safe in old guns. Iron/steel shot is not.

[foresterdj]

Well yes, I get that the shot is compressed, but since shot is pressing on shot it would seem that little to no inward momentum is imparted to the shot.

I would love to see some ultra slow motion of the shot clouds as they leave the barrel. Has anyone seen these anywhere?

[Prairie dog shooter]

"Then when I consider that the ML shooter has (between some minimum and maximum amount) a basically infinite range of load ounces available (vs the conventional loads commercially available for breach loading shotguns), and when I consider that pattern density that matters is the actual number of pellets in the target area (not a percentage), is it not just as easy (or easier even) for the ML shotgun shooter to affect actual shot pattern density by changing load exiting his straight bored gun and just forget all about this jug choking idea?"

Yes.

I use a Jiffy muffin mix shot buffer in my 20 gauge Chief's Gun with hard plated shot.  I get full choke patterns from that cylinder bore.  I also tinkered with card and wad combinations to get the tightest patterns.  A friend gets very tight patterns using tow as wadding over powder and shot.  So one can get a good turkey load from a cylinder bore.  If I wanted a dedicated turkey gun I would get a jug choked barrel and skip all the load development.  But I enjoy the versatility of the smooth bore and having a load for round ball, shot, and turkey.

[Daryl]

Well yes, I get that the shot is compressed, but since shot is pressing on shot it would seem that little to no inward momentum is imparted to the shot.

I would love to see some ultra slow motion of the shot clouds as they leave the barrel. Has anyone seen these anywhere?

I think that is an erroneous supposition about inward momentum as this "shadowgraph" from Greener's 9th Edition of The Gun shows.
As you can see, there is a lengthening/stringing of the shot column when fired from a choked bore, whereas the non-choked shot column remains shorter.
This was "taken" some time before 1900, I believe.

[Daryl]

Shot size chart:

[Hungry Horse]

 In a couple of recent videos on YouTube I was stunned when I caught a glimpse of the muzzle of these two trade guns. They looked for all the world like a chunk of heavy gas pipe. After re-watching these two episodes it was obvious that compared to my old trade gun built from an old (1870’s) shotgun barrel these guns were muzzle heavy. Are these intentionally made with an excessively heavy barrel to allow them to be jug choked?


Hungry Horse

[axelp]

As a warning... ITX non- lead shot is NOT recommended to be shot out of full choked barrels. It is a mix of powdered tungsten and iron, with a soft binding agent all heat injection molded into pellets of specific sizes. It will not deform, and that is why it creates really nice patterns. But you can easily crush the shot sizes with a pair of pliers. My Jim Chambers PA Fowler loves ITX shot. I have taken one turkey with it, and a couple handfuls of gray squirrels.

Another caution-- its harder than lead and will break your teeth if you bite into it.

With my full choked 12 g, its standard lead or bismuth shot

K

[foresterdj]

I am surprised there has not been more to the direct question.

From a Field & Stream article there was this.



Visually we have all seen this, and accept the idea. However, I am pretty sure from years of wildland fire suppression spraying water and monitoring pump pressures, that the reason a restricted nozzle sprays farther is the constriction of the outlet building added pressure, which pushes the water farther (or the shot in this analogy). When, if the same pressure could be run from an open ended hose the water would go as far.

So a regular choke constricting the otherwise straight bore might follow this idea. It would seem a jug choke that gets bigger (lowering the pressure) and then constricts to the original bore (going back to the original pressure?) would not follow.

Obviously, actual results people have shooting patterns with a given gun as cylinder bore and then after that bore is jug choked indicate something is happening. This is just a physics, internal ballistics, puzzle I do not understand.

[axelp]

I see what you are getting at. Interesting.

A  jug choke, in theory, starts with a set pressure and that pressure decreases at the wide space, but as it constricts again, it can only increase it back to the original-- or less--which is a gradually decreasing pressure as it travels the length of the barrel.

I believe a jug choked barrel works differently than a standard choke. It seems to offer less benefit than a standard choke as well, --but enough to offer measurable benefits.

Maybe a standard choked barrel benefits from both the physics exemplified by a water hose and the physical redirection of the shot into itself, Where the jug choked barrel only benefits from the redirection of the shot itself
?

It is a bit of a tootsie pop question-- at least to this under educated mountain boy.

K

[Daryl]

There are several different 'systems" of choking.
Compressed muzzle add-on was first developed in the mid 1800's by Pape & is pictured in Greener's "The Gun".
This system is also used on cheap single barreled shotguns that the muzzles are run into a die to squeeze metal of the muzzle to a smaller diameter, thus the Swaged" choke.
Another is the Jug choke, an enlarged section behind the muzzle, somewhat longer than the shot cloud, so the shot charge can expand, then hitting the forward constriction
back into the muzzle, the shot column is compressed again, and exhibiting improved patters.
Another is a constriction behind the muzzle, a tightening of the bore, then a straight section to the muzzle, which is called the "end bore". This "End Bore" should be of the same
length as the shot column.
Others are skeet chokes and the spreader choke, which does not choke(constrict) the shot column, but does the opposite.

[axelp]

You beat me to it. Here is an interesting article on the history. It does not explain the science of it so much...

https://sportingclassicsdaily.com/choke-tube/

[foresterdj]

That is a good history read, thanks.

[Daryl]

You beat me to it. Here is an interesting article on the history. It does not explain the science of it so much...

https://sportingclassicsdaily.com/choke-tube/

That was a decent article. I was not aware Paper and Roper were so close together - memory and all that. The first "The Gun" was written in 1858, however.
The 9th edition, the one I have, was written in 1911 (I think) by WW Greener, W.Greener's son.
It is an immense volume of 804 pages with VERY interesting anecdotal entries, photographs, add reprints, etc, and noting the loads, wads, and 'contests in shot gun patterning' done in
Britain throughout the decades up until 1911, as well as rifle's of the ctg. period starting in the 1870's.
I've read it 3 times, but not for several decades.