Velocity E.S. vs Vertical Dispersion at 1,000 yards

[Len Backus]

How low do you tune the muzzle velocity ES (10 shots)of your loads in order to shoot small groups at 1k?

Ballistics programs tell us that a 30 to 50 fps velocity difference will cause a vertical spread of quite a few inches, depending on the bullet's BC. How much correlation do you actually see (as opposed to theory) between ES and vertical dispersion at 1k?

[meichele]

Hi Len,

I have shot some factory ammo that was about 60 FPS ES and it would group 10" at 1k. I have some home made loads that have shown me as much as 70 FPS differance and they give me less than 4 or 5" of verticle separation at 1k. Strange huh??

[LDO]

typically 1k shooters try to tune there loads so that the ES is in the single digits.i know i dont have to tell u this but the key to lr. accuracy is consistency,a ES over 20fps is not considered consistent enough.with tiny groups being shot all the time by a number of shooters ,its important to use any edge u can get,a low ES would be one of those competetive edges.my-2 -dave-merry christmas

[milanuk]

This is one of those 'weird' subjects. I agree, by my beer logic, a lower E.S. (and by way thereof, S.D.) should be a given for long range shooting. Makes sense. But from time to time, I hear shooters (good, long range competitive shooters... not BR, but Palma) mention that when they got around to chronographing a load that they'd been knocking out the 10/X rings w/, the chrono numbers seemed to indicate that they shouldn't even be able to keep them on the paper at distance. And that's one *big* honkin' target frame! Almost seems to indicate that there might be something else at work here?

Kind of a sub question that's been bugging me every time I come across it in 'Handloading For Competition: Making the Target Bigger' by Glenn Zediker. He mentioned something he'd heard second hand, so I don't know who started the rumor, but supposedly some people who had the setup and patience to do so had chrono'd their loads both at the muzzle, and at 1000 yds. The weird part was that the individual rounds showed much, much less E.S. *at the target* than they did at the muzzle. Any ideas on how that works?!?

TIA,

Monte

[a.JR]

Most of the chrono's used by the average shooter do not have the capability of resolution of any less than 15 fps,Mainly because of the screens capability, so the guys that have the need for single digits do not have the full story..Obviously if you have figures of 75 fps you are not going to be kickin "A" at Hawks Ridge,but concentration on group size at the chosen distance will net more positive results than focusing on the chrono ..JR..Jeff Rogers.. pic of 3 targets shot during the state champs @547 yds they are 1.230 /1.910 /2.400 = agg 1.84ins and these were shot with a rifle that has a variation of 25 fps on my chronograph

[STL_Shooter]

That would seem possible given the bullet leaving the barrel at a different point in its vibration...

[RBrowning]

You not only have faster and slower bullets leaving at different times in the barrel's vibration pattern, you have the bullets leaving at different points in the recoil cycle. Logically we assume, supported by all of the balistic printouts, that the lighter bullet will shoot flatter and hit higher. I have seen many times when the lower velocity bullet hits higher. The slower bullet is in the barrel longer and the muzzle has raised farther due to recoil. Not a big issue with a 50 pound bench gun but more obvious with sporter weight rifles. This becomes very obvious when changing to heavier bullets in a pistol and your point of impact at 100 yards goes up instead of down.