The following thought has had me wondering what I might have missed in your various discussions about choke and the work of Warren Johnson on his choke selector.
Some of the numbers in my example are guesses but close enough to give you the idea. Adjust the numbers to your experience and see if you don’t have an answer close to mine.
The issue is the significant difference in choke selection for a given target at a given distance if it is crossing vs. going away (ie. trap target).
An average shot shell’s shot string has a velocity of 800’/second at 30 yards. If the size of the effective volume of shot inside the Gauss curve at 30 yards is 4′(L) x 24″(D) it will take 1/200th of a second to move that 4′ core past the target’s line of flight at that distance.
Given a crossing target at 30 yards moving at 45 mph.
45mph = 66’/sec=792″/second
In 1/200 of a second it has moved approximately 4″
The movement of 4″ inside the curve effectively increases the size of the target by 80%.
Use what ever criteria you want to define what is necessary to break a target (2 pellets @ .9#, 2 @1#) the bottom line is……………assuming you agree!
Open Up on crossing targets until I get my revised “Choke Chooser”.
Your student in arms,
I am going to forward this to Warren Johnson (inventor of Choke Chooser) because I know that he will do a better job on this than I can. That said, you just KNOW that I can’t resist sticking my oar in the water (usually only to find out that it is over my head).
My tendency would be to stick with the tighter chokes espoused by Choke Chooser. Yes, as the target moves through the pattern it presents its five square inch side view over a 4″ path. This might seem to indicate that you actually have a larger target and thus should be able to open your choke.
In reality, I don’t think that this is the case. You have to also take into account the fact that the shot is arriving in that (using your example) four foot shot string. At any given moment, the shot available to strike the target is very much less than the stationary pattern indicates due to shot stringing. Depending on the quality of the shell, a pattern shot on a stationary piece of paper that prints a modified 60%, will turn into an improved cylinder pattern or even less if you get that piece of paper moving at target speed.
Bob Brister demonstrates this dramatically in his book “Shotgunning: The Art and Science” when he has his wife tow a long piece of pattern paper on a trailer frame behind the family station wagon. Instead of having all those pellets go into a neat little circle, if that pattern paper is moving the circle becomes an ellipse. Naturally, spreading the shotload of pellets out to cover an ellipse means that there are fewer to fill the 30″ circle in the center that is supposed to harbor your pattern.
So, on a crossing target, your choke prints a good bit more open than it does on a straight away target. Frankly, I don’ t know if this compensates under/over/the same for the extra target exposure as it moves through the pattern. There are a ton of variables. Much of that may depend on the quality of the shell and its particular shot string length. Cheap shot strings more than hard shot, fast load more than slow, rough barrels and bad chokes more than good. You must add also to this the fact that shot string increases dramatically with distance. An answer that is correct at 20 yards will be way off at 40. Now if we could just factor in the lunar cycle and tide tables.
I will send this off to Warren so that you can get a real answer.
Shotgun Report’s Technoid
(Often in error, never in doubt.)