ES/SD vs Group size

[bmart2622]

So Im working up loads for my 300 Ultra. I used Ramshot Magnum and Retumbo. I shot a 10 shot group of each. The Magnum had a SD of 15 and ES of 42 and shot a .875" 10 shot group. The Retumbo had a SD of 8 and ES of 24 but shot a 1.1" 10 shot group. Do I go with on target accuracy or numbers?

 

[Rob5589]

A true 10 shot .875 group would be the end of load development for me. Either group actually.

 

[JFK]

I’d go with on target accuracy.

 

[A382DWDZQ]

Accuracy.
This is from a Ruger American All Weather Compact I got at Walmart for $428 in September 2022. ES159, SD60…0.6 MOA. I’ll test a few more charges around this one to see if it holds, and if it does, I’m going to be pretty happy to have it dialed with over half a box of bullets left.

 

[MCS]

It depends on how far you plan on shooting. If your at 500 yards with a high es you will still hit your target. If you go to 1500 yards with a high es you will miss the target most of the time. I try to get my es down in the single digits but I will accept a es in the teens.

 

[bmart2622]

Shooting steel out to 1000 and game at 600-800 max if necessary

 

[Mag_7s]

I'd play around with seating depth with the retumbo. I would bet you can tune that load.
Having a wild es, but good group cost me a fantastic muley at 800 a few years back. Never again will I choose a smaller group if the es is higher than 25.

 

[TxLite]

Figure out what distance you’ll be shooting game at, then punch in the highest and lowest velocity achieved for each powder into a ballistic calculator and determine if it will still be in the vitals at your target distance. If both powders will do what you’re wanting then I’d pick the smaller group size to account for shooter error.

Just my 2 cents.

 

[A382DWDZQ]

Shooting steel out to 1000 and game at 600-800 max if necessary

Ah, at those ranges, my 159 ES wouldn't be much use. That would be 7", 17", 31" at 600, 800, and 1000. With 24 ES, it more palatable... 1", 3", 5". That load I posted above is for a max of 300yards, and probably well under 250.

 

[bmart2622]

There was 1 big outlier that skewed the whole group, without that one I would have had an ES of 24 and and SD of 9. I shot 2 groups of 5 and within each 5 shot group was a .266" group and a .438" group with the other 2 shots touching each other

 

[MCS]

Shooting steel out to 1000 and game at 600-800 max if necessary

I don't think you will have very good success with those numbers. What bullets are you using? What brass are you using? How are you measuring your powder?

 

[bmart2622]

Norma brass, 200 Gr Accubond, Rcbs Chargemaster Link verified on a beam scale.

 

[bmart2622]

I'd play around with seating depth with the retumbo. I would bet you can tune that load.
Having a wild es, but good group cost me a fantastic muley at 800 a few years back. Never again will I choose a smaller group if the es is higher than 25.

I might load 5 up seated .020 each way of the group I shot today and see what happens

 

[Ddubs20]

When doing ladder tests to find the nodes, I usually see that a super low single digit es /SD isn't usually the best grouping at 200 yds. Usually close by is a node with es/SD in the teens or twenties that groups best. But if I would shoot the Lowest es/sd node at 500 yards or further I would think it would group better the further out you go.

 

[MCS]

Norma brass, 200 Gr Accubond, Rcbs Chargemaster Link verified on a beam scale.

I'd try a different bullet then the accubond for long range. The accubond works great on animals but they have a lot of inconsistieces and are not the best choice for long range. The 210 berger with rutumbo in the rum is a great combo.

I personally cut my es down when I stopped using my chargemaster lite. I found that the lyman gen 6 had a more accurate scale.

I've had good luck with norma brass.

 

[bmart2622]

Tried Bergers, Eldx and Accubonds; the Accubonds were the most accurate so far. I double check every charge on a beam scale to ensure accuracy.

 

[Mag_7s]

I might load 5 up seated .020 each way of the group I shot today and see what happens

If that shows promise maybe work in .005 increments. Secant ogives are know to be a little more temperamental than tangent. I'm sure you know that, but that's why I would think the Noslers are showing better accuracy.

 

[bmart2622]

Ive found small seating depth changes to yield very little change, often not worth it

 

[MCS]

Tried Bergers, Eldx and Accubonds; the Accubonds were the most accurate so far. I double check every charge on a beam scale to ensure accuracy.

Bergers are more sensitive to seating depth. I run vld's at .010 or less off the land and a hybrid I start at .015 off the lands. When I used to run accubonds the seating depth didn't matter as much and the eldx was not as sensitive to seating as a berger.

 

[bmart2622]

Im sticking with the Accubonds