Calculating Leads


Dear Technoid,

A couple of friends and I were checking our reloads with a chronograph to see if the four gauges were shooting close to the same FPS. We noticed some of them were around 115 FPS different.

My question is, at what fps difference in the shells, does it make a difference in the leads for skeet?

I don’t know if I phrased it right, so, if you have a 410 load that shoots 1320, would there be a noticeable difference in your lead if your 20 was shooting 1200 ?

I can’t get a permit to carry a slide rule, so I thought I would ask you.

Thanks a lot,
Don

Dear Don,

First of all, gauge doesn’t matter. All you care about is time to distance. If everything starts out at the same speed #7-1/2s have slightly better time to distance than #9s do because the larger pellet retains energy a tiny bit better. At 20 yards is almost isn’t enough to measure, but at 40 is is.

I don’t have the exact numbers for #9s in the tables, but a #8 started at 1145 fps takes .063 seconds to reach 20 yards. The same #8 at 1255 (110 fps faster) takes .058. Even though you are dealing with slightly higher speeds, it is the difference of .005 seconds that counts.

Let’s say that your target is going about an average 35 mph (a pretty average speed for a skeet target). That is 51.33 feet per second. .005 x 51.33 = .26 feet.

So the difference in lead on a 90 degree crossing 35 mph skeet target (station four) between a load of #8s at 1255 fps mv and one at 1145 fps mv is about three inches. At that distance, using #9s instead of #8s won’t throw the calculations off enough to matter.

Boots off, beer open.

Best regards,

Bruce Buck
Shotgun Report’s Technoid

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