Extreme Spread: Calculators vs. Real World

[Wheres-Waldo]

In the quest everyone seems to be a part of, searching for and utilizing methods to reach into single digit extreme spreads, I can’t help but wonder in the real world results of an ES of “x” and the same value in a ballistic calculator are in agreement.

I’ll use my ballistic information as an example:
Berger 105 Hybrid at 3060 FPS has 253” of drop at 1000 yards. An extreme spread of 10 FPS results in a variation in drop that is just a tad over 2” at that distance.

Obviously, the slower the projectile at the range in question, the larger a variation in elevation you will have for any given ES, but from the perspective of what difference it has on target according to the calculator, not many of us can hold elevation that tight in a lot of positions.

In your experience, does real world vertical spread correspond with this?

(I know real world brings in MANY more variables that may influence vertical, but let us consider a perfect world/conditions)

 

[MakeSawdust]

There are a lot of things that can disrupt that. I only have 775 yds to test. Group dispersion and a phenomenon called positive compensation can disrupt the simple vertical dispersion caused by velocity variation. There is also vertical dispersion caused by bc variation from bullet to bullet.

One of the best loads I have ever shot had horrible chrono numbers. When I started shooting long range I didn't have a reliable chrono, so I just recorded my trajectory and the conditions and made the calculator match those. No chrono needed. I worked up loads by what had the smallest groups at 775 yds (used ocw process to get there, but ultimately fine tuned this way).

When I bought a magneto speed I wanted to see how my load was for consistency. The load hammered. It was easy to make a 1" splat on the 400 yd target and a 1.5-2" splat on the 600 yd target and it shot several 10 shot groups between 2-3.5" at 775 yds. There was basically no vertical and it was mowing down kyl racks. It is still the most accurate load/gun setup I have had several barrels and thousands of rounds later.

To my surprise, a 10 shot string would have an SD between 15 and 17 and an ES that was 40-50fps. It made no sense, but it repeated itself very consistently until the throat eroded significantly.

I'm sure at greater distances the velocity variation would have started to show up, but out to 1000 yds the load worked way better than it should have. The moral of the story is to believe what the target says. If you are trying to develop a load for elr without access to elr distances then it is prudent to find a load that will shoot tight with good chrono numbers. However, my experience and that of others has proven that you can have a load that shoots better than the numbers say it will.

 

[Steel head]

Generally I find it fairly easy now to get a SD of 5-8 over 10-20 shots.

Could improve that a bit with a better scale and maybe more in depth brass prep.

One thing that surprised me was when I tried some of the new Berger LRHT bullets.
With the same ES my vertical noticeably improved to the holy crap category.
My last barrel legit held a foot of vertical at 2000 yards in great conditions.
Hopefully this barrel follows suit.
I’d imagine a similar thing is seen with quality solids.
Gave me a lot of confidence when reaching way out there.

I’m a fairly lazy reloader so going all in is probably not gonna happen.
Thankfully with a good base you can get away with a lot.

 

[AKMarty]

Interesting read at the end of this article regarding the question of how much does it matter. I’m still working to get a consistent loading process down. I’ve got my SDs down to the low teens and occasionally high single digits.

https://precisionrifleblog.com/2020/04/28/bullet-jump-research-and-load-development-tips/