Advanced Marksmanship mover lead rule of thumb

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PaulStafford

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Minuteman
Jul 31, 2010
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#1
Hi all

I was looking at several references on leads for movers, and thought that a rule of thumb would be nice, so I set to work with excel, and came up with this.

Rule of Thumb: The lead <span style="text-decoration: underline">at any range</span> is 0.50 mil per mph of target speed. So for a 3 mph target, a full value lead would be 1.5 mil.

This rule of thumb is quite accurate for 2900 fps, but still quite close for other MV. For example, at 2700 fps, the lead is .543 mil, which is close enough. This seems simpler than anything else I've read. It does make a simplifying assumption of constant bullet velocity, but see below for analysis of differences.

The background math is straightforward, and I have the equations/spreadsheet if anyone is morbidly interested.

Here's 2 examples using 2928 fps MV.
At 100 yds, 1 mil = .300ft, TOF is .102 seconds. A mover at 1mph is moving 1.466 fps, and moves .150 ft during TOF. So the mover moves .15 ft/.30 ft per mil = .50 mil.

At 500 yds and 3mph (4.4 fps) mover, 1 mil = 1.5 ft, TOF is .512 seconds, and the mover moves 2.25 ft. Thus, 2.25ft/1.5 ft per mil = 1.50 mil lead.

OK, so bullets slow down. How much effect does that have? I used JBM to see what the real TOF would be (.308, 2928 fps, BC= .6), and calculated the resulting mil leads for a 1 mph target speed. As you can see, it remains fairly accurate to at least 6-700 yds. Lower BCs would exaggerate this a tiny bit.

distance actual mil lead required
100 .513
200 .526
300 .541
400 .556
500 .571
600 .588
700 .606
800 .624
900 .644
1000 .665

Comments?
 
#3
Re: mover lead rule of thumb

My rule of thumb is to check my data card dangling off my rifle with a 3fps lead on it and adjust according to target speed I ballpark with my reticle (one of those reticle uses where linear measurement at distance that is so derided by many here actually comes in handy).
 
#5
Re: mover lead rule of thumb

Sounds close to what we used at the FN/Leupy match at Ft. Meade. No notes in front of me but we calculated the speed of the mover based on the time of exposure. The target was exposed for 70 ft. I think we came up with 2.65 mph and shot 1.5 mils with the wind and 1.7 against at both 200 and 300 yards. Both leads were spot on.
 
#10
Re: mover lead rule of thumb

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">I use 0.6 mils per mph of target speed perpendicular to the line of fire, but that's with a .308 moving around 2600 fps. Close enough.

Of course, the real trick is to know how fast the target is moving.
</div></div>

Lindy,

do you do a count of 3 sec's and divide mil to gain target speed speed at distance?

John
 
#11
Re: mover lead rule of thumb

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sobrbiker883</div><div class="ubbcode-body">My rule of thumb is to check my data card dangling off my rifle with a 3fps lead on it and adjust according to target speed I ballpark with my reticle (one of those reticle uses where linear measurement at distance that is so derided by many here actually comes in handy). </div></div>

My method also. We shoot movers out to 600 yd. several times a year and scores have steadily improved. For people powered movers a 2 to 2.5 mph speed is very close. I've settled on dialing lead and tracking target. A 5 to 10 mph wind really makes it interesting.

So do you guys dial or hold lead with reticle?
Do you trap or track?
 
#12
Re: mover lead rule of thumb

75% of the time I trap, it is my prefered method. And I always hold for movers. You never know when it will stop, change speed, or change direction.

On a range when the mover is on a track, yea you know how fast it is moving and where it is going. But it is my experience that if you dial for a mover, it can come back to bite you. I always hold but thats just my method.
 
#13
Re: mover lead rule of thumb

John:

Techniques like that work at matches, where the target cycles back and forth at consistent speeds, and you can do the calculation while someone else is shooting.

It's not a useful technique in the real world, where exposures are often brief. By the time you use that technique to figure the target speed, then figure out what lead to use for that speed, the target will be gone.

I find it more useful to estimate the target speed by eye as a slow walk (2 mph), a faster walk (4 mph), or a run (make an eyeball estimate), then use the 0.6 mil/mph ROT to figure the lead.

The other tip I have is to get a lot of practice shooting moving targets, which, alas, is difficult for many people to do.

And if I am shooting a mover at a match, I estimate the target speed, calculate my lead, and watch where the first shot goes, correcting as necessary on the next shot. That requires that your technique be good enough to watch where the shot hits downrange, which is a useful skill to develop.
 
#15
Re: mover lead rule of thumb

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">John:

Techniques like that work at matches, where the target cycles back and forth at consistent speeds, and you can do the calculation while someone else is shooting.

It's not a useful technique in the real world, where exposures are often brief. By the time you use that technique to figure the target speed, then figure out what lead to use for that speed, the target will be gone.

I find it more useful to estimate the target speed by eye as a slow walk (2 mph), a faster walk (4 mph), or a run (make an eyeball estimate), then use the 0.6 mil/mph ROT to figure the lead.

The other tip I have is to get a lot of practice shooting moving targets, which, alas, is difficult for many people to do.

And if I am shooting a mover at a match, I estimate the target speed, calculate my lead, and watch where the first shot goes, correcting as necessary on the next shot. That requires that your technique be good enough to watch where the shot hits downrange, which is a useful skill to develop.
</div></div>

Very valid, I was just thinking for match use, when yote hunting I use the reticle as well, still track them.
 
#16
Re: mover lead rule of thumb

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">John:

Techniques like that work at matches, where the target cycles back and forth at consistent speeds, and you can do the calculation while someone else is shooting.

It's not a useful technique in the real world, where exposures are often brief. By the time you use that technique to figure the target speed, then figure out what lead to use for that speed, the target will be gone.

I find it more useful to estimate the target speed by eye as a slow walk (2 mph), a faster walk (4 mph), or a run (make an eyeball estimate), then use the 0.6 mil/mph ROT to figure the lead.

The other tip I have is to get a lot of practice shooting moving targets, which, alas, is difficult for many people to do.

And if I am shooting a mover at a match, I estimate the target speed, calculate my lead, and watch where the first shot goes, correcting as necessary on the next shot. That requires that your technique be good enough to watch where the shot hits downrange, which is a useful skill to develop.
</div></div>

This works.

I was going to say the math is great but what happens when your target is varying speed or quartering away and ducking and dodging debris. I would try to learn instinctive lead if you can.

A good example of this is the Deer I shot last year. When it busted out of the Aspen Trees it was going away at about 10 degrees at a full run. I busted his front leg with the first shot. He went into the trees and the next view and shot was at about 75 degrees and I hit him in the Ass. The third shot that put him down was at 90 degrees. This all happened in about 15 seconds at 400 yards.
 
#17
Re: mover lead rule of thumb

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Learn from others mistakes. You will not live long enough to make them all yourself.</div></div>

Perhaps, but I sure seem to be trying...
laugh.gif
 
#18
Re: mover lead rule of thumb

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">I use 0.6 mils per mph of target speed perpendicular to the line of fire, but that's with a .308 moving around 2600 fps. Close enough.

Of course, the real trick is to know how fast the target is moving.
</div></div>




......and which way the wind blows
 
#19
Re: mover lead rule of thumb

Oh, <span style="font-style: italic">now</span> you want to make things difficult...
laugh.gif


Actually, it's not difficult. If the target is moving into the wind, add the wind hold to the mover lead.

If the target is moving downwind, subtract the wind hold from the mover lead. If the number is negative, that's how far to hold <span style="font-style: italic">behind</span> the target.

And all of that is an example of why Jacob Bynum of Rifles Only said, "Successful application of the precision rifle is a lot more about thinking than it is about shooting."
 
#21
Re: mover lead rule of thumb

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">....well.....i'm off to happy hour now.....but i'll try to figure which way the wind blows</div></div>

Well, it's election day, and I think the wind is blowing to the right.

I'm off to Happy Hour, too. TTFN!
 
#22
Re: mover lead rule of thumb

"Successful application of the precision rifle is a lot more about thinking than it is about shooting."


That my friends is very well said...anytime I have made a mistake at a match it is ALWAYS me not the gun ... nice quote
 
#23
Re: mover lead rule of thumb

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KNIGHT11B4</div><div class="ubbcode-body">75% of the time I trap, it is my prefered method. And I always hold for movers. You never know when it will stop, change speed, or change direction.

On a range when the mover is on a track, yea you know how fast it is moving and where it is going. But it is my experience that if you dial for a mover, it can come back to bite you. I always hold but thats just my method.</div></div>

Ambush, and trap and hold are techniques I can just barely muster. And, leading a target is not something I can confidently do. Problem is, ADD AGAINIST/SUBTRACT WITH wind calculation, as well as 45 degree movement. So far,these things I cannot understand quick enough in the fleeting time available to always correctly counter for the condition.
 
#24
#25
Re: mover lead rule of thumb

"I'll take 'the penis mighty' for $100 Alex......."

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BOLTRIPPER</div><div class="ubbcode-body">....well.....i'm off to happy hour now.....but i'll try to figure which way the wind blows
DSCN1048.jpg
</div></div>
 
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