Calculating Leads


Hi Bruce

This is a question that most shooters would run very fast from. I have read most everything on the various bird leading methods, and Understand them. 95% of the birds I encounter are over a wonderful pointer, so crossing shots are rare, (thank God) the only two birds I missed last season were crossing, out of 41 pheasants. I do brush up on skeet prior to hunting (about 200 rds a year) but crossing pheasants just don’t seem the same, like take the speed, approx. 35 mph verses approx. 55 mph on skeet?

This is my outlandish question: Take a crossing Pheasant at 38 yards, speed 35 mph with no wind (fast bird), a 12 ga. 28 inch mod choke on an O/U, 2 3/4 #5 shot nickel plated max powder (hot stuff).

Now here is the kicker, take all human variation out, NO swing speed, and just the center/middle pellets from the 8 ft shot string hitting the bird in the head, How many feet/inches of a lead would be required? If it sounds like a crazy question that serves no good reason, you may be right, but what if you had a great point and pull type shooter, that was outstanding at judging distance, could he not hit Pheasant with regularity with no swing at 38 yards?

Thank you for indulging a shooting nut by reading this, even if you don’t come up with the lead distance.

Mike

Dear Mike,

No, it’s not a silly question at all. These things are fun to know. According to Lowry’s Ballistics program [no longer available] to get time of flight (.1161 sec) and then a little math, a 35 mph right angle crosser at 38 yards using a 1-1/4 oz 3-3/4 dram (1330 fps) load of #5s would require 5.96 feet lead. This would be the lead whether or not you were swinging like crazy or had the gun bolted down in a vise.

The variations are interesting. If you slowed that load of #5s down from 1330 fps to a more modest 1220 fps, your lead would only increase to 6.44 feet. That’s less than six inches. Your energy would be 2.82 ft/lb as opposed to the 1330 fps #5 at 3.20 ft/lb.

All of this is pretty academic. Let’s say that you mis-judge your distance by 5 yards. That’s pretty easy to do. If the bird were really crossing at 43 yards, using that load of #5s at 1330 fps, your lead would increase to 7.01 feet. That’s another full foot of lead- a meaningful amount when you consider that your killing pattern is 24″ at best. I don’t know about you, but I sure can’t tell whether an airborne pheasant is 38 or 43 yards away. Maybe I could spot the difference between 30 and 40 yards, but I’m not absolutely positive of that either. The difference in that lead would be 4.40 feet vs 6.37 feet, or about two feet. That is enough to cause a clean miss. It’s sometimes amazing how we can hit anything at all.

One more point while I’ve got coffee in the cup, no matter how fast you swing your gun it does NOT influence lead! No kidding. It really doesn’t. That garden hose analogy simply is not scientifically accurate. You can’t “spray” shot by swinging faster. No matter whether the gun barrel is stationary or moving like crazy, lead is fixed by where the barrel is pointing at the moment the shot emerges from the muzzle. Swing after the shot has left obviously doesn’t help. Swing while the shot is in the barrel may impart a very slight lateral vector, but compared to the speed of shot it isn’t enough to matter. Only the time when the shot is half in the barrel and half out can the movement of the muzzle possibly “spray” shot. That time is very short and the shot is protected in a plastic shot cup, so it really is a moot point.

To test this I once wasted half an hour standing on a hillock right beside a lake. I swung my gun like crazy as I shot, but all I got were the typical oval pattern that I also got when I just aimed the gun. Live and learn.

If you like to fuss with ballistics, try the KPY Shotshell Ballistics Program Version 2.0. That will give you your time to distance for all loads and all you have to do is work the TTD numbers into actual leads.

One last point: You only missed two out of 41 pheasants last year?! Atta boy! Geez, I wish I could shoot like that, but I can’t. One thing’s for sure, you are smart enough to use #5s. That pellet size will definitely put a few more birds in your pouch than #6. With percentages like that, why are you asking me about leads. I ought to be asking you. What ever you are doing must be right.

Best regards,

Bruce Buck
The Technoid writing for Shotgun Report, LLC
(Often in error. Never in doubt.)
http://www.ShotgunReport.com

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