I don't understand how chokes work to shape shot pattern..

[fiddler]

Chokes are simple. they squeeze the shot cup as it passes the muzzle. When your shot cup opens up your pellets will spread. The tighter it got squeezed, the longer it takes to open and spread the pellets.

Therefore:

If the shotcup only has a light squeeze or none at all, it opens up quickly and the pellet spread begins at close range.

If the shotcup has a tight squeeze (full choke) it will take longer to open up and cover more distance before the pellets begin to spread.

 

[Aniest]

Always best to pattern your shotgun with the ammo you use. I have a .410 Baikal that I use both #8 for target shooting and #4 for hunting: the improved modified is the tightest pattern with both (yes, tighter than Full)... and the Improved Cylinder is the same pattern as the Cylinder but gives a more consistent pattern on both.

Somehow, as FLHTCUI said, there are more things at play than just the choke's ability to make the shot in the cup conform to a pattern.

 

[kennymo]

Why all the insistence that the shot cup comes into play so much? Chokes worked long before anyone had ever thought about inventing such a thing. It is the forcing of the shot together that affects the pattern, the main advantage of the cup seems to be less shot deformation in the barrel which improves pattern somewhat, especially with lead shot.

 

[fiddler]

Why all the insistence that the shot cup comes into play so much? Chokes worked long before anyone had ever thought about inventing such a thing. It is the forcing of the shot together that affects the pattern, the main advantage of the cup seems to be less shot deformation in the barrel which improves pattern somewhat, especially with lead shot.

Sure, I will go with that, but what rounds do you use that don't have a shotcup? There are many variables that affect shot spread, but why make it complicated to answer a simple question? If your answer was given to a classroom of noobies, not one of them would be able to explain it or understand it an hour later.


Just wait until someone feels gravity, temperature, barometric air pressure, and the atomic values of the materials are needed to explain something simple.

 

[guntech]

Plastic shot columns (wads) do two important things better than the old (basically discontinued) over powder wads. They seal gases more efficiently and give a much more uniform pattern.

It turns out a plastic shot column also increases the effect of the existing choke slightly... so those really old shot guns with very tight full choke barrels with modern shells are really extra full.

Modern factory manufactured lead slugs can be fired through any choke designation. You may find better accuracy with some constriction over a cylinder bore.

So with lead shot you get better patterns for longer range with quite a bit of constriction... modified and full chokes...

This is not true with steel shot...

SHOTGUN BARREL ALTERATIONS FOR STEEL SHOT

Forcing Cone Alteration:

Factory shotgun barrels usually have a fairly short and abrupt forcing cone. The forcing cone is the tapered area just ahead of the chamber where the shell is contained. Altering the forcing cone, so it is one and one half or two inches in length, reduces recoil and improves the pattern density. Trap shooters and skeet shooters have been doing this for many years. It is a good benefit to the steel shot user as well.

Choke Alteration:
Choke designation from the tightest to the most open are:
Extra Full, Full, Improved Modified, Modified, Skeet II, Improved Cylinder, Skeet I, and Cylinder Bore.

Steel shot does not require the constriction that lead shot needs, to produce good patterns. In fact too much constriction, causes poor, erratic patterns, and in some cases, permanently damages the barrel. I have seen barrels bulged at the choke, I have seen barrels where the choke split right open, from using steel shot.

For steel shot, with thin barrels, chokes should be altered to at least Skeet II. Often, over & under, and side-by-side shotguns, are best altered to Skeet I and Skeet II chokes. Heavier barrels can be left at Modified choke but may see an improvement in the pattern if opened slightly.

 

[gabrielguitars]

Sure, I will go with that, but what rounds do you use that don't have a shotcup? There are many variables that affect shot spread, but why make it complicated to answer a simple question? If your answer was given to a classroom of noobies, not one of them would be able to explain it or understand it an hour later.

Lots of people who who shoot older guns load shells with no modern plastic shot cup, but that is a discussion for another time and thread. As far as complicating the answer, I don't believe he complicated it at all - the simple fact is that the answer is complicated, and honestly, is a room full of noobs remembering the explanation really the watermark of a proper answer? Really. The simple answer has already been given, so it's fair to look into the more in-depth reasons for why choking the barrel works. To that end, it seems there is not simply the fact of how squeezed together the shot becomes at the end, so much as how much constriction it experienced. This may sound exactly the same, but there is a difference.

Some decades ago, a gunsmith was making a different kind of choke that was finding excellent results. It is known as a Tula choke, or a jug choke, IIRC. His idea was to bore a larger section in the barrel behind the area of the choke. What this would do is to allow the shot to spread first into the over-bored area and then constrict back down to cylinder bore just before it left the barrel. This was a way to create a choke in a cylinder-bore barrel without fitting the muzzle with interchangeable chokes. Think of it this way; if he bores out a section of barrel from the standard .729" to .769", the shot would first expand to the new barrel diameter of .769", and then experience the same .040" constriction found in a full choke, but only as it comes back to standard bore diameter! I think that's pretty cool, but is quite needless these days, and can also beg questions of bore sealing, etc. The point of his experiments in this discussion is that it doesn't appear to be how tight the shot column is when exiting the barrel so much as how much constriction it experienced just before it left the barrel. Now that everyone is thoroughly confused, my work here is done.

Edit: I should explain that this fellow's chokes were being used before the advent of modern plastic wads, and that is very significant to understand.