ES vs. Groups Size - 7mm Rem Mag Load Development

[b-harvin]

Hey all, this is my first time working up a load. So far, I've done a ladder test to work out powder weight and then tested seating depth groups off of the powder data (see below for details). The problem I'm having is I either get good SD/ES with larger groups, or tighter groups with high ES. If I was just shooting out 100yds, I'd be perfectly OK with the group size and look past the ES. But, ideally I could shoot out 600+ and I'm worried the high ES will really start to show at those distances. Here's some more data...

Rifle: Rem 700 Long Range - 7mm Rem Mag
Usage: Hunting (would like to shoot out to 600 yards)
Bullet: Berger 168g VLD Hunter
Powder: H1000
Brass: Hornady
Primer: CCI 250

Here's what I shot this AM @ 100 yards:

68.8 Grains - 5 shot group with an ES of 102

71.2 Grains - I only shot 3 with an ES of 19

Original ladder test (.002 off rifle lands)

And my seating depth tests based off of the Burger website recommendation. Had about a 12-15mph right to left wind. I only shot this with 71.2 grains because I thought the ES was better and would therefore producer smaller groups. Maybe I should do this again with the 68.8 load?

Any guidance on my next step would be appreciated. Thanks in advance.

 

[AckleymanII]

If you have some retumbo, start at 68g and work up, fed 215 bullet .020 off the lands to start. R#25 will also give you some very low eS with a Win mag primer, you will not believe the speed.

I shoot Remington 700 sporters, 26", muzzle break, bedded, floated, jewel trigger, and they all shoot tiny groups. Retumbo and R#25 is the mack daddy with 160-168g bullets, and Retumbo seems to prefer 215's and R#25 loves Winchester mag primers, with single digit ES.

Bullets touch at 100.

Gentry muzzle breaks through a lot of noise down ranges as their ports are slanted forward about 15*.

Williams Muzzle breaks make the 7 mag kick like a 223!

I wear peltor Tac 6 electronic ear muffs, and since I started wearing them, I hear a lot of deer snorting and snort wheezing that I never heard before.

 

[savagedasher]

If you have some retumbo, start at 68g and work up, fed 215 bullet .020 off the lands to start. R#25 will also give you some very low eS with a Win mag primer, you will not believe the speed.

I would check your rest or the shooter . All but one showed too much horizontal. Heavy trigger pull can do it also . Larry

 

[3081FTR]

Putting some arbitrary numbers in to the Berger ballistics calculator using the 168 match vld BC.

3020 = 66.13 inches of drop at 600 yards
3039 = 65.6 inches of drop at 600 yards

I'm not saying ES doesn't matter but does that amount of theoretical variation matter in your application?

If it doesn't then you might be best focusing on the load that performs the most consistent from one day to the next.

Not saying you can't have both a consistent load and a small ES either, just food for thought in your load dev.

I don't do ladder tests as such but understand that they are difficult to interpret if completed at 100 yards. You might better served looking at Erik Cortinas 100 yard load development thread for load dev if thats the distance you have to work with.

One question - with your seating depth test, did you measure each loaded round or just adjust the seating die?

Groups .090 and .130, how confident are you that it wasn't wind that pushed the one shot out? I think you need to decide what it is you are looking for in your load development, most tend to ignore horizontal and are looking for reduction in vertical. There are caveats to this statement, as there is lots of evidence out there that suggests some loads can shoot small but are somehow still more wind sensitive.

 

[Mozella]

You don't have to be a ballistics expert to appreciate the fact that launching each round at exactly the same MV should be a good thing when it comes to shooting small groups at long distances. As someone with lots of physics training in my background, I believe this to be a fact. How could it be otherwise? The idea is obvious to any kid who ever threw rocks.

Unfortunately, my faith in physics doesn't match very well with my ballistics testing results.

Just like you, I also worry about ES and SD in my hand loads. I happen to log SDs but for this discussion, differences in SD and differences in ES will show the same trend. And like you, I am disappointed that good groups don't always match good ES (or SD) and vice versa. Here is a chart of several thousand rounds showing SD vs MOA and Group Height, all are 5 shot groups using .223 ammo.

SD vs Performance

Some of the worst SDs produced the smallest 5 shot groups. The scientist lurking in me finds that odd, hard to explain, disappointing, and bothersome.

As someone shooting a .223 in 600 yard F/TR competition, I do my best to reduce SD (and ES) but based on my testing and measurement I've stopped worrying too much about it. No matter how much I've tried, I can't find SD paradise. So I now concentrate on finding the recipe which gives me the very best precision and I let the SD and ES fall where they may.

In other words, my approach to SD and ES is now more a state of mind than anything else. I load my competition ammo based on the components, charge weights, and loading procedure which produces the best precision ON THE TARGET, not some recipe which produces low SDs or small ESs.

By the way, the SDs and ESs for my 6mm BR are always lower than those for my .223, but the lack of correlation between SD and MOA is still there.

In short, I've stopped worrying about my SD problems. I think wife-beaters call this "Conflict Resolution" and unhappy people call it "Stress Management".

It should be noted that last Saturday I won an F/TR match with my .223 and out scored all the F/Open shooters too. The next day I shot a 600 yd BR match with my 6mm BR and shot the best score and the smallest group as well.

I don't know what all this means, but I keep reminding myself that where I compete they hand out prizes (and a little money too) for the guy with the best score on target, NOT the best SD or ES.