Home Forums Hunting & Shooting Long Range Hunting Velocity spread. What is acceptable?

Good day.

I am posting this question here as it does not have as much relevance at 'normal' hunting distance. What do you guys see as acceptable regarding velocity spread when shooting out to a 1000y?

Thanks

Pieter

Preferably single digit ES's, but under 20 is acceptable.

At 1k a 15fps change is a 6" elevation difference. That puts me out of the 10 ring and dropping a point. Also would put me out of the boiler room on a deer. Really need single digits shooting that far but extremely hard to do.

In my .243AI flinging 105's at my locale, a 15 fps change only accounts for 2.8" of vertical at 1000. In my 7WSM with 162's it's only 2.6"...

208 AMax, 2600 fps. 15 fps is a 4.3" change at 1K.

In the 308 Win, I believe a heavier bullet helps even out velocity spread. Can't prove it, but I believe the added inertia helps even things out.

To me, less than 20 but I prefer my 308 to be closer to 10

I'm not sure I trust chronographs to be accurate enough to be a reliable indicator of vertical spread. Shot a 5 shot group at 600 yards the other day from my .308 with 155gr Scenars launched at 2865fps. 4 of the five had about 1" of vertical. The other shot opened it up to about 2" vertical. Point being that is much less vertical spread than my chrono indicated it should have produced. Chronographs are nice and I use mine extensively, but the most reliable results are what you see on the target.

John

I also have had some outrageously good groups from loads with less than stellar ES and SD. I always wonder if my chrono is not as accurate as it should be when that happens.

BINGO. The correct answer is here. I still hope for low, but I always trust paper over computers and theories every day.

The physics won't lie, but the problem is getting accurate and statistically significant data. Trying to use SD numbers based on a sample of 5 or 10 shots is like thinking that you'll never get into a car accident because in 5 or 10 trips to the grocery store it hasn't happened yet. To get accurate SD numbers, you need to use 10 or 20 times that many sample shots.

Add into the equation that chronographs, even the very best ones, have up to 0.5% error, meaning that with a load that averages 3000 fps, you'll have a 15 fps error margin. It's hard to get a reliable SD or ES number when up to 15 fps difference could be entirely chronograph error.

Thats why you shoot paper at the distance you have as max.

And you shoot lots of it. In fact when in competition, I rarely was sure of a load unless I"d shot it at least 4 months in weekly matches every weekend... that meant probably 32 groups of 10 shots or 16 of 20... that was a start at seeing if it was good enough.

There's an awful lot of people that don't have the gun and/or ability to shoot the ES difference at 1000 yards, let alone have the knowledge, time, expense, or desire to build the loads that might.

I regularly shoot out to around 880 yards(I have shot close to 1000Y but the spot I am shooting from now is set up at between 600 and 880Y) and my my hits are pretty consistent. My cold bore shots have been very good and my vertical adjustment has been spot on. What made me wonder is that I get good consistency regarding accuracy but my chrony regularly gives me a velocity spread of around 20fps.

Pieter

So why would you believe a machine over where the holes are in the paper..

I think one reason why I wondered about it, is when I shoot or hunt in different areas with different altitude and weather it would be more comforting knowing exactly what velocities of different loads are at zeroing weather/place. I do think my velocity spread is probably less than the crony indicates at times, as accuracy has been good but maybe trying another crony might reveal more.

Pieter

The target is the only thing that matters. If the group is holding the water-line it doesn't matter what the chrono says about E.S.s. If the come-ups aren't matching the drops, then either the chronograph or scope is lieing to you so you end up lieing to your program to make it work.

In the end you have to go to the target, so it is just as easy to start there.

How many loads don't vary by 20fps just due to normal morning/mid day temp changes, even with say hodgen extreme powders? Curious how common that is even with the best of loads?

Also, if you think about a 15 fps change equalling 5" at 1000 (extreme spread), then wouldn't you really only see a 2.5" difference since your zero would represent the middle of the spread?