Introduction

On this page, over a period of time, we intend publishing information and tips covering many different aspects of shooting.

SHOTGUN CHOKES is the first subject we would like to introduce, a topic few people understand , and we trust this explanation will deal with this problem. Shotgun patterns dictate the CHOKING of any particular shotgun, REGARDLESS OF WHAT IS STAMPED ON THE BARREL OR CHOKE. Choking is the constriction in any barrel, which on average, dictates the pattern percentage, although this will also change when using a variety of ammunition (lead shot, nickel plated shot etc). Pattern percentages should be taken at a distance of 40 yards, at a piece of paper with a 30" circle. The amount of strikes within the 30" circle, compared to the number of pellets contained in an identical unfired shotshell, will result in a percentage. For example, if one were to use a 12GA 28gram No 7 ½ shotshell, which contains 400 pellets, fired at the 30" circle resulting in 200 strikes within the 30" circle, the result is 50% , and therefore the choking of the barrel would be Improved Cylinder (British Standard). If one were to use the same load 28 grams, but using Nickel Plated shot , will usually result in a tighter pattern , as nickel is harder, and less likely to deform on the way down the barrel. The result would probably be 55% , and therefore the choking would be ¼ choke (British Standard) The best patterns, are the ones without any excessive holes through which your target could escape, and therefore even patterns, are the most efficient for breaking targets, or killing birds in flight.


  British Standard Constriction Pattern % @ 40 yards
  Cylinder
Improved Cylinder
¼ Choke
½ Choke
¾ Choke
Full Choke
.000 inch
.005 inch
.010 inch
.020 inch
.030 inch
.040 inch
40%
50%
55%
60%
65%
70%
       
  American Standard    
  Cylinder
Skeet
Improved Cylinder
Modified
Improved Modified
Full Choke
.000 inch
.005 inch
.010 inch
.020 inch
.030 inch
.040 inch
40%
53%
57%
67%
73%
75%
       
  Italian Standard ( Beretta )    
  Cylinder
Skeet
Improved Cylinder
Modified
Improved Modified
Full Choke
.000 inch
.002 inch
.005 to .010 inch
.020 inch
.030 inch
.036-.039 inch
40%
  -
50-57%
60%
65%
70-80%
       
  European / Continental Standard ( Browning )  
  CL ( Cylinder )
**** Improved Cylinder
*** ½ Choke
** ¾ Choke
* Full Choke
.00 mm
.25 mm
.50 mm
.75 mm
1.0 mm
40%
50%
60%
65%
70%
       
  Briley Choke Tube Specifications  
  Cylinder
Skeet
Improved Cylinder
Light Modified
Modified
Improved Modified
Light Full Choke
Full Choke
Extra Full Choke
.000 inch
.005 inch
.010 inch
.015 inch
.020 inch
.025 inch
.030 inch
.035 inch
.040 inch
 
       
  Winchester    
  Cylinder
Skeet # 1
Improved Cylinder
Skeet # 2
Modified
Improved Modified
Full Choke
.000 inch
-
.005 inch
.007 inch
.012 inch
.022 inch
.036 inch
25-35%
33%
45%
50%
45-55%
55-65%
65-75%
       
  Shot Size Details      
  Designation Dia/mm Dia/inch Shot Count per ounce (28grams)
         
  LG
SG
Special
SSG
AAA
BB
NO 1
NO 3
NO 4
NO 5
NO 6
NO 7
NO 7 ½
NO 8
NO 9
9.1
8.4
7.6
6.8
5.2
4.1
3.6
3.3
3.1
2.8
2.6
2.4
2.3
2.2
2.0
.36
.33
.30
.27
.20
.16
.14
.13
.12
.11
.10
.095
.09
.085
.08
6
8
11
15
35
70
100
140
170
220
270
340
400
450
580
         
  Shot Size Equivalents          
  English Metric American French Belgian Italian Spanish
               
 

LG
SG
SpSG
SSG
AAA
BB
NO 1
NO 3
NO 4
NO 5
NO 6
NO 7
NO 7 ½
NO 8
NO 9

9.1mm
8.4mm
7.6mm
6.8mm
5.2mm
4.1mm
3.6mm
3.3mm
3.1mm
2.8mm
2.6mm
2.4mm
2.3mm
2.2mm
2.0mm
-
00 Buck
1 Buck
3 Buck
4 Buck
Air Rifle
2
4
5
6
-
7
8
-
9
-
-
C2
C3
5/0
1
3
4
5
6
-
7
7
8
9
-
9G
12G
-
-
00
-
-
-
5
6
7
7 ½
8
9
-
11/0
9/0
-
-
00
1 or 2
3
4
5
6
7 ½
8
-
9 ½
-
-
-
-
-
1
3
4
5
6
-
7
7 ½
8
9
               
  Number of Pellets per Shot Load        
  Weight grams Weight Oz #3 #4 #5 #6 #7 #8
                 
  46
42.5
36
34
32
30
28.5
26.5
25
23
17.5
16
12.5
9
1 5/8
1 ½
1 ¼
1 3/16
1 1/8
1 1/16
1
15/16
7/8
13/16
5/8
9/16
7/16
5/16
228
210
175
166
157
149
140
131
122
113
87
78
61
44
276
255
213
202
191
181
170
159
149
138
106
96
75
53
358
330
275
261
248
234
220
206
193
179
138
124
97
69
439
405
338
321
304
287
270
253
236
219
169
152
118
84
552
510
425
404
383
361
340
319
298
276
212
191
149
106
732
675
562
534
506
478
450
422
394
366
282
254
187
141
                 
  Percentage of Total Pellets in 75cm Circle          
  Boring of Gun
Or Choke
      Range in Metres  
    20 25 30 35 40 45 50 55
                   
  True Cylinder
Improved Cylinder
¼ Choke
½ Choke
¾ Choke
Full Choke
75
85
90
97
100
100
63
74
80
86
93
100
53
64
70
76
83
90
43
53
58
64
70
74
35
43
48
54
58
62
28
34
39
43
47
51
22
27
31
34
38
41
18
22
25
27
30
32
                   
  Choice of Shot Size for South African Gamebirds and Clay Targets
  Quarry /Target Shot Size Quarry/Target Shot Size
         
  Guinea Fowl
Quail
Egyptian Geese
Teal
Yellow Bill Duck
Bush Doves
Skeet ISSF
Skeet English
Olympic Trap
4 or 5
8 or 9
1 or 3
5 or 6
5 or 6
8 or 9
8 or 9
8 or 9
7 ½
Francolin
Partridge
Spurwing Geese
White Face Duck
Rabbit / Hare
Rock Pigeons
Skeet USA
Trap DTL
Sporting FITASC
5 or 6
5 or 6
BB or 1
5 or 6
3 or 4
7 or 7 ½
8 or 9
7 or 7 ½
7 , 7 ½ , 8 and 9's


© Suburban Guns 2003