III. Firearm Information by Type
     E. Shotguns
         2. Barrels and Chokes
            c. Chokes

by Scot E. Heath (scot@hpfistu.fc.hp.com)

> By the way, is there any book I can get to help figure out when to use what
> choke?  I use a Skeet choke for Skeet, Improved Cyl for Trap, and an Improved
> (U)/Modified(O) combination for Trap doubles.  But I haven't the foggiest
> of when I need to change chokes for Sporting Clays.  I know I can pattern
> my gun, but what is considered an optimum pattern?

You are the first person I have spoken with who actually uses too open a
choke for the sports you described.  To choose a choke, you need to
estimate the distance at which you will be breaking the target.  Sporting
clays is by far the most difficult to judge due to the wide variety of
situations encountered.  Let me see if I can give you a "rule of thumb"..

In trap singles, you stand 16 yards behind the thrower.  The average trap
shooter breaks the targets at around 40 yards.  The chokes used typically
range from modified to full.  This means that the actual pattern range is
enormous since a choke is considered modified with as small as .015"
restriction while a choke is considered full with as much as .045"
restriction.  I personally shoot an improved-modified (NOT Improved
Cylinder) choke for trap singles, handicap (27 yard) and the second shot in
trap doubles.  My particular improved-modified choke is .025" restriction.
I chose this choke by 1) patterning my gun and 2) noteing the way the
targets break when I shoot them.  My choices were modified (.015"
restriction), improved-modified and full (.035" restriction).  At 40 yards,
the modified choke in my gun with my loads gave about a 36" pattern that
was "full of holes" meaning that there were several areas on the paper that
were big enough for a target to fit with no holes.  The improved-modified,
on the other hand, gives about a 30" pattern that is very uniform.  The
extra 10 yards in handicap is a concern but I have chosen to shoot #8 shot
from the 16 yard line and #7.5 from the 27 yard line.  My #7.5 loads
pattern enough tighter than my #8 loads that my patterns are nearly
identical 10 yards apart.

For trap doubles, I use the modified choke for the first shot.  This is
because the first shot in trap doubles is typically broken at around 30
yards and at that distance, the pattern from the modified choke looks fine.  

I normally tell people to choose the choke they think will work and then go
1 choke more open because as components improve, patterns from the same
choke get tighter.  Todays modified choke is typically as tight at 40 yards
as a full was 20 years ago, due entirely to the improvements in shells.

In your case, I would say go 1 choke tighter than you have been using in
trap.  I don't know what your particular chokes measure but I would use at
least a modified for singles and perhaps a modified/full for doubles
although, if you have a tight chokes, your combination for doubles could be
ok.

One way to judge is by how hard the birds break.  If you get right in the
center of one, you should just "powder" it.  If you never get anything but
big pieces,  you are shooting too open a choke and because of smaller
pellet concentration, you will have birds that should break but don't.  If
you are getting alot of "dust" off targets but they don't break, you could
be using too open a choke.

> I sort of think of the chokes as gears... if I get a 30-inch pattern with
> Skeet at 16, then I need to change to Improved to get a 30-inch pattern at
> 20.  Will this type of approach work?
> 

This is the correct approach but as I said, there is such a wide variety of
restrictions called the same thing, the only way to know how your
particular gun shoots is to pattern it.  A skeet choke typically has about
a .005" restriction and this is because the distance at which most skeet
targets are broken is between 5 and 15 yards.

When I shoot sporting clays, I try and relate the shot I have to make to a
shot in either skeet or trap, something with which I am vastly more
familiar.  I typically shoot #8 shot and then choose a choke based on my
estimated "shot relation".  If the shot is an incomming over the head type,
like pad 8 in skeet, I use a skeet choke.  If it is a springing teal
launched from 20 yards or less, I will use Improved/cylinder, maybe
modified.  One of the courses I shoot has a station where the targets come
out over your head and move away from you.  It's a true pair and the first
target is broken at about 30 yards, the other at about 50.  I use improved
-cylinder, improved-modified for this station.

To give you somewhere to start, estimate the distance at which you will
break the target and then use the following table:

  distance  |   choke
____________|___________
            |
  0-15 yds  | skeet
            |
 10-25 yds  | improved-cylinder
            |
 20-35 yds  | modified
            |
 30-45 yds  | improved-modified
            |
 40-55 yds  | full
            |
  > 50 yds  | prayer

As far as books go, I think one of the best books I have read which covers
a wider variety of disciplines is "Finding the Extra Target" by John Linn
and some senator who wanted to get his name on the book.  John Linn is the
winningest coach in Collegiate Trap shooting and unfortunately, just passed
away this year.  The book is available from, I believe Shotgun Sports
magazine.  I unfortunately have loaned my copy out so I can't give you any
more specifics right now but I will remind myself to do so in 2 weeks or
so.

Good shooting,

-Scot