Heavy vs Fast

[Timetoshoot]

At First the idea of going lighter and fast made a ton of sense. New left hand gain twist 6.5 CM barrel 22”. likes three loads, and im now in the process of choosing a load for next summer.
all three .5 MOA for 10 shot groups with .7 to .9 sd
147eldm at 2750 (temp stable dope verified to 1000 yards)
130hyb at 2825. (temp stable dope verified to 1000 yards)
135classis Hunter at 2920 (RE26 worked up as hunting load don’t think it will be stable in summer heat dope verified to 800)

I shoot year-round most of my shooting in is between 5300 feet and 9000 feet elevation.
At 1,000 yards Looking at windaged with a 10 mile an hour full value wind the 147 has.2 mil advantage over the 130 and .1 advantage over the 135
Again at 1,000 yards looking at elevation 135 is king with a ..9 mil advantage over the 147. And the 130 has a .3mill advantage over the 147.

in This situation the 147 Is not as flat shooting as the other two rounds, but it holds the wind better. At 1200 and 1400 yards it maintains its advantage. I’m better at reading a dope chart than I am at reading the wind. . It’s also cheaper to load and I have not seen any of the reported problems with the 147.

so my question is; Given this data set is there something I’m missing that would encourage you to choose the lighter faster bullet?

 

[brianf]

as you said...anyone can read a drop chart or a kestral with DA

its a lot harder calling wind

i want every advantage i can get when trying to read the leaves and grass

 

[Bayoubigcat]

I’ve done this exercise several times and theres typically very little difference. Just plugged in the wind into the ballistic calculator I use to see what wind difference a 0.1 mil variance looks like with 147s (2780, sea level, 70*) and got a 0.6 mph difference in wind per 0.1 mil (10.7 mph = 1.8 mil, 10.1 mph = 1.7 mil)
So my thoughts to you are that:

If you can call the wind to within 0.6 mph (or whatever it happens to be in your case with the three different loads you listed) then your bullet selection matters.
And if 3.6” (0.1 mil at 1000) is the difference between a hit or a miss your bullet selection matters.

 

[fvalmostthere]

I did this same exercise with 140 and 130 hybrids and 123 scenars. I went light because the differences in wind at 1000 were minimal and they were cheaper to load. In a prs match most of your shots are going to be inside 800 and I dont recall exactly but it was at least 600 before the bigger bullets had any wind advantage at all and out to 800-1000it was still minimal. Not sure if that is your intended use but that was part of the puzzle for me.

 

[kthomas]

If it's all about ballistics, then pick whatever projectile gives you the least windage uncertainty. We can easily compensate for drop, but windage is more of a guesstimate, the more so the farther you go out.

I don't chase BC anymore. I shoot what my rifles like, and learn the projectile inside out. For me, that's Berger Hybrids in all my cartridges. 105 in 6BRA, 140 in 6.5 Creedmoor and 230 in .300NM.

Pick what's most consistent in your rifle and rock it. Every time I go and try the "new shiny" I end back up at the old faithful Berger Hybrids.

 

[Jack Master]

Hay fellas here is a post Frank put up. This is an easy way to see what caliber/bullet will do the best in the wind.

The Trajectory Normalizing Factor
By: Josh Kunz

The long-range shooting community is a niche market of the firearms world, and that niche is full of myths and misunderstandings about a lot of aspects of long-range shooting. One of the most common is the misconception that just because a caliber is larger or a bullet is heavier, it must therefore “cut the wind” better. Here is a simple, effective, and nearly fool-proof method to get a fast answer to, “which has a better wind call?” that doesn’t involve running ballistics through a calculator.

Many folks want a way to figure out what “the best” combination might be for a given task. This need is many times solved by doing detailed ballistics calculations. In today’s world of handheld computers (smartphones) this approach is much less onerous than in years passed but even today it still takes a lot more time to run a set of ballistic simulations than it does to solve a simple math problem on a 4 function calculator.

The Trajectory Normalizing Factor is a seemingly simple approach developed by myself to perform this exact task quickly and effortlessly when discussing caliber options with customers and friends for rifle building needs.

There are 2 basic inputs that are required and we can ignore a lot of the others that we need for the ballistic calculators. We are going to talk about comparing 2 calibers under identical conditions. Always. It’s not useful to compare combination A at sea level and combination B at the top of a mountain on a hot day. We need to simply know which is better under the same conditions because as those conditions change they change for both options.

Some basic rules and assumptions: Atmospherics are assumed identical.

Drop is important but for trajectory comparisons, it is secondary to the wind. Ignore drop concerns and worry about the wind.

The G-standard for the ballistic coefficients must be the same. The units on the muzzle velocity must be the same.

This means if Combo A uses feet/sec then Combo B must use feet/sec as well and if Combo B uses G7 standard, then Combo A must use G7 standard. Likewise, if Combo A only has data for G1 standard, then Combo B must use G1 or take the G7 value and convert it to G1.

Otherwise, the calculation is skewed.

OK, simple enough. What is TNF?

??? = ?? ∗ ??

Truly that simple.

Sample Calculation:
Combo A: Berger Hybrid 6mm 105gr flying at 3,030 fps (0.275 G7) Combo B: Hornady ELD-m 6.5mm 140gr flying at 2,740 fps (0.326 G7)

Which has a better trajectory?

??? =3,030???∗0.275=833.25 ?
??? = 2,740??? ∗ 0.326 = 893.24 ?

Based on the TNF calculated for each the 6.5mm option has a better trajectory. Below is the 1,000yd solution calculated for 0 DA showing the elevation & wind calls.

View attachment 7218637

In this case the larger, heavier bullet going slower did better than the smaller faster bullet. But let’s look add in a 3rd case where that wouldn’t be true. Combo C is using a 100gr 6mm bullet with a very high BC. Lighter, faster, and better trajectory.

??? =3,050???∗0.318=969.9 ?

View attachment 7218638

Let’s take it one step further by asking “If I have Combo A, how fast do I need to shoot Combo B to have an equivalent trajectory?” This is based on the age-old comparison of 2 bullets in the same rifle. Should we use the 180gr or the 162gr bullet because the 180 has more BC but the 162 can be shot a lot faster? Put more directly, if we have Combo A already figured out how fast does Combo B needs to go for it to be equivalent to Combo A?

Let’s take a look at the author’s 7mm SAUM shooting a Hornady 180 ELD-m at 2,870fps and figure out how fast the 162 needs to be shot to equate the wind call for the 180 at 1000yd?

View attachment 7218639

Soon this concept will be built into a calculator will be available for free on www.patriotvalleyarms.com

Also - Here is the APA website with the orignal data (same article) - https://patriotvalleyarms.com/trajectory-normalizing-factor/

 

[300_BLK]

What type of shooting do you most do with this rifle over summer?

I load for the purpose I use the rifle - if it is hunting then I use the hunting bullet, matches the match bullet or if it's in my crossover rifle (match and hunting) i find a hunting bullet with a good BC like the 143 ELD-X.

This is just what I do, necessity is the mother of invention.

Good luck