Forcing Cone Designs in Choke Tubes

[3" 870 Shell Shucker]

I've noticed that some chokes have a long slow taper forcing cone, some have a shorter quicker taper, and others have what appears to be two different forcing cone sections with different tapers.  Are there any rules of thumb regarding what works best with specific types of loads?

[allaboutshooting]

I've noticed that some chokes have a long slow taper forcing cone, some have a shorter quicker taper, and others have what appears to be two different forcing cone sections with different tapers.  Are there any rules of thumb regarding what works best with specific types of loads?

Then internal geometry of many choke brands is quite different. It all really depends upon what the designer believes works best or sometimes what he is capable of producing or what he can produce at a given price. There are very many factors involved. You have pointed out but one factor of choke design and there are many others of course.

Exit diameter, sometimes incorrectly referred to as constriction is another factor but many times less important than the other "internals" of a choke tube.

As an example, we often see that many shooters recommend a choke with a .670 exit diameter for the overbored Mossberg 835 with an inside bore diameter of .775. That's a constriction of .105 but seem shocked when the engineers at Browning recommend a choke with an exit diameter of .640 for their overbored Invector+ barrels with an inside bore diameter of .742. That's a constriction of .102 somewhat less than the constriction of the .670 Mossberg recommendation.

It's really all about the design and how everything is coordinated and incorporated within that design.

Thanks,
Clark



Thanks,
Clark

[jdavenp3]

I really have no knowledge about this type of thing when it comes to bores and constriction talks. I know you have told me a few recommended chokes for the Invector Plus barrels. I have a question.

How can there be a large difference between the exit diameters of the recommended chokes versus something, like an Indian Creek, with a .665 exit diameter and still have desirable results? That would be a .77 constriction in the IC versus a .102 constriction in the recommended choke tubes.

Is it a lot to do with individual guns, individual ammo loads, plus all of the other factors that make a good pattern (temp, cleanliness, etc.)? If all things are equal will it always favor the recommended size or is it just a sweet spot, feel type of thing? It is late and I don't know why I am rambling honestly. Just wanting to gain knowledge I suppose...

[SumToy]

A lot of it is to slow the wad.  A short taper will slow wad more then a long taper.  Now some of them run a long taper that lets the ports be part of it.  The Two taper choke has been around for years.  The step chokes came out the target world. 

[3" 870 Shell Shucker]

I wasn't going to make this an Indian Creek thread, per se, as I mainly wanted to focus upon the Forcing Cone part of Choke Designs. 

(I think Indian Creek has 4 things coming together in one choke design, and those 4 things work together well; A good amount of Constriction, Wad Catchers, A Long Parallel Section, and the Wad Cutting/Slowing action of the 30 Parallel Ports.)

But sometimes people report that another choke design shoots better in their gun, so obviously Indian Creek isn't the only good option.

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Back to Forcing Cones.......

SumToy said that a shorter, quicker forcing cone taper is better at slowing the wad.  That's interesting.

I would think that a longer, slower forcing cone taper gives the shot in the load more time to adjust to the constriction.

What is the benfit of having two separate forcing cone tapers in the same choke design?  Is it trying to achieve the best of both long and short designs?