Some technical information on chokes

DryFire enables you to select different chokes for each barrel and to tailor its settings for any type of choke.

Chokes

Most people refer to choke sizes by name: cylinder, full, improved, skeet etc. The real problem is that these names vary from country to country (English "half" is US "Modified"), they vary from manufacturer to manufacturer (some provide 5 chokes, some 6, some 7) and they have no standard definition. It is quite possible for one manufacturer's "Full" to have a completely different constriction from another's. Some manufacturers do not give their chokes names - they rely simply on the markings - 1 notch, 2 notches etc.

Normally this does not matter - you pick the chokes that suit you and you stick to them.

However, it is possible to have an objective and standard way of measuring choke and it is very simple to do. Choke is the difference in diameter between the end of the choke furthest down the barrel and the diameter where the shot emerges. This is normally measured in thousandths of an inch ("thou").

A typical pair of values for a "Full" choke would be .735" and .695" giving a choke of .040" (40 thou). A Berretta choke marked with 1 notch ("Extra Full") has values of .735", .685" and .050" (50 thou).

You can measure these values for yourself using calipers (digital ones are nice, they work in metric and imperial and they are not too expensive these days - ask at your local tool or fixings shop.)

Here is an approximate table of 12g values (the US sizes and names are taken from the Briley chokes site).

DryFire simulators accurately take into consideration the chokes you are using and you can define the values for the choke you have in each barrel. If you don't have access to callipers you can use the values in the table above.

The table below shows values for standard chokes provided with a 1999 Beretta 682 Gold sporting 12g:

Nothing is ever simple

There is at least one more factor that needs to be considered with chokes - their length. The distance over which the constriction takes place will affect the tightness (or openness) of the shot pattern. Most manufacturers provide chokes that fit completely within the barrel but many third party suppliers offer extended chokes which, in effect, extend the length of the barrel as well as extending the distance over which the constriction takes effect.

A longer choke will smooth out the effect since the constriction takes place over a longer period of time. In theory this will help to keep the shot pattern together by reducing the number of random-direction pellets coming out of the end of the choke.

So, a complete definition of a Berretta Extra Full choke (one notch) would be a .050" constriction over a 2.01" length without extending the barrel

The table below shows typical choke usage: