CHOKE

[snIPer]

Hi All,
Ive heard a lot of CHOKE and talks of choke etc.

what exactly is Choke??

Also can the choke be altered if so how?

Any views with images will be nice
Thank you.
/S/

[mundaire]

Choke is a constriction towards the muzzle of the barrel. When referring to choke, people almost always are talking about shotguns, even though some rifles too have a slight choke in their barrels to improve accuracy...

Back to shotguns - as you might be aware, shotguns are usually used to fire multiple projectile cartridges, see http://en.wikipedia.org/wiki/Birdshot for more.

To control how these projectiles "pattern" some distance after exiting the barrel, chokes are used. Choke constriction usually varies from zero (true cylinder or no choke) to full choke... in between you have chokes like Improved Cylinder (IC), Modified Cylinder (MC) etc.

In some cases you might find extra open chokes, in which case the choked end of the barrel is actually a little wider than the rest of the barrel, and also extra tight chokes which are tighter than full chokes - like extra full choke, or super full choke...

As you would imagine, the tighter the choke - the less the spread of shot for a given distance from the barrel and vice versa. Many people incorrectly claim that tighter chokes increase the range of the gun - this is COMPLETELY FALSE. Choke only controls the spread of shot.

Of course if you are shooting at shorter ranges, you would want to use more open chokes as you would like a greater spread of shot at closer range - therefore giving you a much better chance of hitting the target; conversely if you are shooting at longer distances you would want the shot to travel further away before spreading out... Which is probably why some people cling to the myth of tighter chokes = longer range!

Earlier, all shotguns used to come with fixed chokes - that is, the choke was part of the barrel itself and therefore could not be changed based on changing shooting needs. Although one can get a good gunsmith to modify a tighter choke into a less constrictive one - such a change would be PERMANENT and if the gunsmith mucks up the job, the damage would not be easy to rectify, you'd probably need new barrels... AFAIK it is NOT possible to get a gunsmith to "tighten" an open choke, say from true cylinder to MC...

These days many of the new shotguns models sport "screw-in" chokes on one or both barrels. This greatly increases the flexibly of the gun, as you can change chokes, selecting the most appropriate one for the job at hand.

HTH

Cheers!
Abhijeet

[snIPer]

Thanks Abhijeet that was very informative.
Also - do ppl prefer different chokes for Trap compared to Skeet?

[spacetraveller]

SnIPer
Abhijeet
AFAIK there are no restrictions by ISSF on choke or cylinder use in shotgun events. But usually in skeet one uses full or true cylinder both barells and in trap the lower barell (first shot) is MC and the top (second shot) is full choke.
Abhijeet your comments awaited.
By the way Abhijeet - today evening - Club-
Spacetraveller

[mundaire]

In Skeet the clays are shot at shorter distances, hence shooters prefer using more open chokes... skeet chokes are most often plain simple true cylinder (i.e. no choke at all)...

I have not had much opportunity to shoot trap, but am quite certain the chokes used for trap are tighter than those used for skeet. Spacetraveller could be right as far as the Improved choke/ Improved modified chokes and Full choke combination. Even the barrels of trap guns are longer than those used for skeet...

Spacetraveller, Which club? What's the POA?

Cheers!
Abhijeet

[HSharief]

I shoot a modified choke for American trap. Like Abhijeet said, the "pattern" will dictate what choke will be the right one to use. Different guns, choke, ammo will pattern differently and you'd want different patterns for different sport/game. Generally tighter for trap than skeet.

I'm sure you guys have heard of the "diffusion" choke or spreader choke. Google it and you'll see. There is also a straight rifled "choke", sometimes the entire barrel, that is used for trap to stop/reduce any spinning of the wad/shot to reduce pellet dispersion.

Use Google, there's lots of interesting info out there related to chokes.

[shooter]

" I'm sure you guys have heard of the "diffusion" choke or spreader choke."

i think it is also called tula choke

[Grumpy]

There are different forms of difuser choke of which the Tula type is probably the best known. The effect does open the pattern a little compared to cylinder choke but the greatest benefit is from the improvement in the pattern. Difusion chokes were quite popular with Skeet shooters back in the seventies/eighties but are rarely seen nowadays - mostly due to the improvent and range of cartridges available.
`Stripper` chokes which strip the shot cup from the shot column allowing the pattern to open very rapidly and without the risk of the pattern being `blown` by the shot cup have also enjoyed a vogue. The latest trend in Skeet is the use of felt wad ( and variant ) cartridges specifically designed to allow the pattern to open very quickly and evenly.

It IS possible to tighten the chokes on guns bored with very open chokes by having recess chokes cut - what the Americans call `Jug` chokes. The bore is `belled` out a couple of inches or so before the muzzle and then tightened again. The increase in bore followed by the constriction relative to the increase acts as choke. For some reason the effect is greater than conventional choke - ie, a 5 thou recess choke is tighter than a conventional 5 thou choke constriction at the muzzle - and there are various theories why this should be.
Obviously the depth that a recess choke can be cut is limited by the amount of metal in the walls of the barrel.
If the barrel walls are thick enough at the muzzle the barrel can be threaded for removable chokes or have an external vari-choke fitted. The latter is only suitable for use on single barrel guns.

The pattern thrown by modern cartridges incorporating plastic shot cups is considerably tighter than felt wad cartridges. This, combined with recess choking if required, makes it possible for old, loosely choked guns to be used very effectively.

[andy_65_in]

Have heard of these choke tubes one can insert in shotguns. are they practical to fit in a SS 12 bore BSA and if so can they be got hold of india.my this gun has improved cylinder and half choke barrels.any suggestions/advise

[Grumpy]

Andy, fitting removable choke tubes is possible with most guns ( providing that the barrel walls are thick enough ) however with double barrel guns the muzzles have to be internally threaded to accept the choke tubes - you can`t fit externally mounted `polychoke` type tubes on a double gun for obvious reasons. Internal threading of muzzles is a precision business and very few gunsmiths around the world are equipped to do the job. The best known being Nigel Teague of Teague Chokes in the UK whose work ( and chokes ) are widely regarded as the best. Certain gunmakers are now offering Teague chokes as standard instead of their own chokes.
http://www.teaguechokes.co.uk/index.html
The chances of finding someone in India who can machine and thread barrels for internal chokes is virtually - if not completely - zero.

[shahid]

For old classic English shotguns the system was Full choke 3/4 choke, 7/8 choke, 1/2 choke, quarter choke, imprved cylinder and open choke i.e. cylinder. Now all modern makers even if S/s offer variable detachable choke tubes. European makers had a slightly different system of defining choke and then there is the choke diameter system where say .710 is full choke for a 12 Bore gun, then there is .719, .729 and so on.

European makers ( some not all ) defines choke in decimals of inch, and later decimals of metric units. A full choke guide and conversion table is there with me from an old issue of Shooting TImes. Will post it later.

[Grumpy]

By the way, another method of tightening chokes - or creating choke where none existed before - is simply to overbore the barrel whilst retaining the original choke constriction or stopping the overbore an inch or two short of the muzzle if cylinder choked. Obviously the forcing cone will have to be cut - or recut.
Only possible if there is enough `meat` in the barrel of course.
Choke is a constriction relative to the actual bore diameter of the barrel and not a fixed diameter - ie 10 thou choke in a 12-Bore barrel bored .710" is the same amount of choke as 10 thou of choke in a 12-Bore barrel bored .744"*. If chokes had a fixed diameter than a very full 30 thou choke in the .710" barrel ( .680" diameter ) would be a 64 thou choke in the .744" barrel. 64 thou of choke would cause all sorts of problems - shot patterns would be `blown`, the shot itself would be distorted from compression and a ring bulge in the barrel would be inevitable. 64 thou is 1.6256 mm !
(* In percentage terms, 10 thou of choke in a .710" barrel is slightly more than 10 thou of choke in a .744" barrel.......and therefore slightly more actual choke. )