At what distance does standard deviation start to really matter?

[Bat Rastard]

I am working with LeverEvolution in 6BR looking for a Varget alternative.
Accuracy looks promising but my SD is high. (31)
At what distance does it matter?
Would more neck tension help SD?
I would like to get out to 500, well actually to 492.
Thanks, BAT

 

[RubiconJoey]

It's pretty easy to plug your velocities into a ballistic calculator. Here's some range cards for Berger 105s. The first at 2619, the second at 2650. At 500 yards your looking at a 1.65" difference between a slow round at 2619 and a fast round at 2650.

 

[Bob3700]

I am working with LeverEvolution in 6BR looking for a Varget alternative.
Accuracy looks promising but my SD is high. (31)
At what distance does it matter?
Would more neck tension help SD?
I would like to get out to 500, well actually to 492.
Thanks, BAT

Bat,
I really don’t think SD matters all that much out to 600 yds. Beyond that, it translates into vertical.
I size my necks with a .268 bushing n run a .2425“ mandrel thru the necks after. That lowers the neck tension a bunch. My SDs run 9-13 fps In a BRX.

 

[L.Sherm]

Apps mean nothing pretaining to E.S and S.D. on target within reason, now ELR it may but the majority of us it doesnt only the target will tell you test at max distance you plan to shoot.

 

[LCazador]

If you ask a 100 benchrest guys they will answer "it's matters little" till you get past 300 yards. Neck tension in a repeater vs. a single shot is also quite another story. Try BenchMark, H322, RL16, N540 are all alternatives to Varget.

 

[RabbitSlayer]

Just plug your min and max into a calculator and that will give you the worst case scenario.

 

[bpd459]

Be aware Leverevolution is a temperature sensitive powder, and will exhibit pressure signs above 80f. A bunch of us HM NW prone shooters were using it as a substitute grain for grain with our .308/155/ 46.5gr Varget loads. Shot great 40-75f. Higher looked like a shotgun pattern.

 

[cdgaydos]

A better estimate of velocity variation (hi to low) when plugging values into a ballistic calculator would be +/- 2 or 2.5x the SD (or 3 for 99.7% of the population variation)… so a 31fps SD would suggest a “slow” shot at 78fps below the average and a “fast” shot at 78 above for an extreme spread of 156fps.

My opinion (as a service rifle shooter) I would be ok with that out to 200. At 300 it’s about 2” (still just about 0.7MOA) difference. At 500 7”… at 600 its 12”… that’s a “bridge too far” in my opinion.

Depends on how big your target is and how precise you want to be I guess.

As far as some things to improve SD… neck tension (the amount and reduction in variation), perhaps primers. I saw improvements in SD by brushing the inside of case necks with a nylon brush dipped in graphite… reducing friction reduces the absolute values of variation…

If you have to try too hard, might not be the best powder for the application…

Good luck and let us know what works!
Chris

 

[LCazador]

^^^ this. If you have to try too hard, might not be the best powder for the application!

 

[L.Sherm]

Explain this, ive shot this 3 different times all the same result 18-21 E.S.
I've also shot my 30-28 with 3 rounds exactly same fps and it shot 1.5 moa now at 28 E.S it shoots 1.5" 3 shot groups at 665 nice triangles.
The lowest E.S my 30-28 has ever shot really good has been 23 E.S.
Targets dont lie.

 

[L.Sherm]

Targets like above and what I've seen from others proves to me positive compensation is real.

 

[cdgaydos]

Explain this, ive shot this 3 different times all the same result 18-21 E.S.
I've also shot my 30-28 with 3 rounds exactly same fps and it shot 1.5 moa now at 28 E.S it shoots 1.5" 3 shot groups at 665 nice triangles.
The lowest E.S my 30-28 has ever shot really good has been 23 E.S.
Targets dont lie.

I assume you are commenting on my post? If not apologies….
There are other components to variation in the “group” besides the variation caused by differences in velocity… and it can be up or down, left or right… more to the point, however, you are seeing ES of 20 fps, which would be about 2” at 600 yards for a 6BR (95SMK). The calcs I did above were for 156fps and only accounted for changes in vertical from velocity differences. Also, for a larger number of shots, the true dispersion would start to show on the target.

Nice shooting!
Chris

 

[L.Sherm]

No opologies necessary, its just that people strive for single digit E.S and think its the holy grail of good tuned rifles. I do have some rifles that do shoot single digit E.S very well but thats not the " end all be all" the target is.

 

[Bat Rastard]

The LevereVolution is looking pretty good at 100. I will keep trying.

I can always go back to Varget. The Leverevolution throws so nice through my measure.

 

[Bill Norris]

No opologies necessary, its just that people strive for single digit E.S and think its the holy grail of good tuned rifles. I do have some rifles that do shoot single digit E.S very well but thats not the " end all be all" the target is.

Absolutely correct. Erik Cortina shot a 5-shot group @1000 yds. on video that measured 1.4 inches with an E S of 19.

 

[Jeff Porter]

Depends on your target. Benchrest or F class will be a lot closer than a sling target.

Using the numbers in the Tables above on a sling target you would be 0.75 moa or less and hit an X or a mid ring 10 out to 900. You could get a 9 at 1000 pretty easily as that is just over 1 moa difference and the 10 ring is 1 moa from the center.

F class that is a wide 9 after 600 and an 8 at 1000.

 

[L.Sherm]

Doesn't matter if its hunting, F-Class or BR.
If 1 shot is suppose to be x higher because a ballistics calculator says it is and its not well then what. Like I said I shot that exact load for my 6.5x300wsm 3-3 shot groups and essentially 9 shots and they all waterlined, why out of the 9 were none 2" vert

 

[L.Sherm]

Same thing with my 30-28 why did 3 shots exact same FPS shot 7" vertical 4" wide and E.S of 23 and 28 will shoot 1.5 at 665

 

[cdgaydos]

No opologies necessary, its just that people strive for single digit E.S and think its the holy grail of good tuned rifles. I do have some rifles that do shoot single digit E.S very well but thats not the " end all be all" the target is.

Very true, there is no place on the scorecard for muzzle velocity variation! … and nobody brags about low ES after dropping a bunch of points on the target…

 

[tom]

I haven't shot paper past 2,075 yards, so I would answer somewhere 2,076 or more. That said, 31 on SD is quite a lot. My experiences referred to above are more like trying to see 20 vs 5 on the ES, and more often than not the paper will print opposite of the crony.....but only out to 2,075 lol.

Tom