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Forums10
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Apr 27th, 2024
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Joined: May 2011
Posts: 1,136 Likes: 37
Sidelock
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OP
Sidelock
Joined: May 2011
Posts: 1,136 Likes: 37 |
I am wondering if the spread of a shotshell is logarithmic? The reason I ask is I have a pattern board that only holds a 36"x36" piece of paper so I plan on using a 30" circle at 30 yards. Would that be equivalent to a 40" circle at 40 yards, practically and/or theoretically? Could I make the same assumptions about the choke size?
Nothing is foolproof to a sufficiently talented fool.
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Joined: Jan 2002
Posts: 1,278 Likes: 11
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 1,278 Likes: 11 |
Dr.WtS
Mysteries of the Cosmos Unlocked
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Joined: Mar 2005
Posts: 709
Sidelock
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Sidelock
Joined: Mar 2005
Posts: 709 |
Pattern the gun is the best way. If the shot string is above the speed of sound then the shot is going against a near vertical "wall" of compressed air. The shot string will close and slow very rapidly. Even the fastest load is subsonic somewhere around 20 yards. Then the normal flat plate drag laws associated with subsonic flight take over. That is usually an expansion of one inch per yard of travel. It's extremely hard to calculate because the shot coming from the barrel is very irregular and will make for a large and irregular bow wave. The speed of sound varies with the temperature so the the time spent for the shot to remain supersonic can vary. You are dealing with an irregular vehicle (shot group) and a quick change of temperature change from shotgun barrel to ambient traveling in the trans sonic speed range. Given the variables patterning the gun is the best way to get the information you want.
Last edited by pooch; 03/04/17 01:20 PM.
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Joined: May 2011
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Sidelock
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OP
Sidelock
Joined: May 2011
Posts: 1,136 Likes: 37 |
Sorry but I only understand about half of what you have written regarding supersonic and subsonic and the impact each has on the pattern. When you wrote 'pattern the gun is the best way', are you suggesting to test it at logarithmic distances i.e.. 10, 20, 40 yards? I'm not sure what impact shot string has on the pattern?
Nothing is foolproof to a sufficiently talented fool.
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Joined: Jun 2008
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Sidelock
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Sidelock
Joined: Jun 2008
Posts: 2,736 Likes: 96 |
All about drag when a projectile comes back through the sound barrier and passes through its own shock wave in a way. More a problem for long range target shooters. A 7.62mm. military bullet comes back through the sound barrier somewhere around the 900 to 1,000 yard mark and gets very upset and unstable before it settles down again. I've put them all in the black at 900 yards and then had a job finding the target when dropping back to 1,000. Shotgun patterns are 3 dimentional and as Pooch says, each pellet will be a slightly different shape and even travelling at a slightly different speed even after a few yards so it is very difficult to predict mathematically. Interesting question none the less. Lagopus.....
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Joined: Mar 2005
Posts: 709
Sidelock
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Sidelock
Joined: Mar 2005
Posts: 709 |
Forget logs. Just pattern the gun. Experiment with the shot load you are most likely to use and compare, an analog solution, but it is not logarithmic.
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Joined: Jan 2002
Posts: 13,149 Likes: 1147
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 13,149 Likes: 1147 |
Tamid,
I can't answer that question for you, but I can tell you that in my experience you will learn a lot more from patterning at distances shorter than 40 yards than you will from not patterning at all. You can learn a lot at 30 yards and less.
SRH
May God bless America and those who defend her.
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Joined: Jan 2002
Posts: 737 Likes: 23
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 737 Likes: 23 |
Stan is right. A lot of bird shooting is less than 40 yards so I think you learn a lot by patterning at distances that you actually shoot.
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Joined: Jan 2002
Posts: 623 Likes: 1
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 623 Likes: 1 |
Stan is right. Pattern the gun at ranges you expect to shoot. That will tell you if you are going to succeed!
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Joined: Jan 2002
Posts: 5,954 Likes: 12
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 5,954 Likes: 12 |
Tamid, this s a very good question. Unfortunately, the answer is complex. Fortunately, Dr. A C. Jones addressed this question in his book "Sporting Shotgun Performance." You can get an intuitive idea of performance/pattern comparisons by "eye-ball integration" of patterns. However, it would be more worthwhile to use the shotgun insights program to generate statistically valid data.
Briefly, patterns have a Rayleigh distribution (you can use a normal distribution with only a small loss of accuracy) from muzzle until the shot hits the ground. That said, pattern can be calculated up and down the range once it is established. The fly in the ointment is that the diameter of the effective area of the pattern blooms for some distance (influenced by choke) and then withers as the number of pellets becomes insufficient to cover the ever expanding pattern area.
The expansion is not a log function. The following estimate is not too far off: 10 yds to 20 yds - double, 20 yds to 30 yds -double, 30 yds to 40 yds - 1.5X, and 40 yds to 50 yds - 1.5X. Keep in mind that this does not give you effective diameter, rather linear area.
Hope that helps some.
DDA
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