ES/SD contributing variables

[JMRhino]

To all,

In your experience, in terms of the hand loading process, what is the biggest contributing factor to improve ES and SD numbers? I’m chasing my tail. I am guessing that neck tension is probably the most likely suspect.

I know it doesn’t really matter for short to intermediates hunting ranges but just trying to improve…

Thanks.

JR

 

[JD338]

There are many variables such as
Seating depth, neck tension, primers and different lots of powder.
I strive for low ES and SD numbers but sometimes I've gotten a good group with high ES and SD's.

JD338

 

[Blkram]

I believe that consistency and attention to detail is the key to good ES/SD numbers. Control the variables to attain this.
Case length verified, trued primer pockets, properly sized cases, consistent pressure when seating primers, measure each powder charge, and when seating the bullet, start the bullet, rotate the case in the press (helps with straightness) and finish seating, with a good crimp. (How I was first taught to load; has worked well for me). Work up in increments to max, checking for pressure, and backing off as needed.
For years, I did not check neck thickness and did not turn the necks...so not yet sure on this...and did not have a chrony...yet managed to make some pretty accurate loads.
I now have the means to do this, and record ES and SD, as well as check run out...so time will tell, as I practice these more advanced reloading techniques...but with eyesight not what it once was, the human variable may be changing too and we'll have to see how well I continue to produce accurate loads, or if the aging nut behind the trigger is the bigger variable, despite better handloading technique!

While lower ES/SD numbers offer better potential for accuracy, as stated above, some of the most accurate loda do not have the lowest ES/SD numbers.
I am wondering how often ambient temperature, humidity, and your elevation is impacting this...but as I have not tracked these variables over the years, with the various powders, so I don't know... yet...but I plan to start tracking this to see what the results will show.

 

[Orezona]

I recommend you try the Redding Body Die to bump .003 and a Lee Collet die to follow. It works for me. And drop short and trickle.

Edit: And Lapua brass

 

[jimbires]

mag primer / standard primer . too much , or not enough .

 

[IdahoCTD]

If you suspect its neck tension then you can buy a bushing die like the Redding type S or turn the necks on your brass. I generally turn necks on all my brass, even premium brass like Lapua, ADG, etc and I have no problem getting sub 15 es and single digit isnt uncommon. I also tend to jump .2-.3 in charge weight when I'm close to a velocity node. Primers can have a decent impact on velocity as has been mentioned.

I forgot to add that turning necks is what many of us did prior to bushing dies to control neck tension. A bushing die only helps with consistent neck tension if the brass is consistent. Cheap brass is far from consistent and even premium brass varies some. That is why I turn necks.

Low ES and SD is important for vertical dispersion at long range but accuracy is just as important as low ES/SD. Ladder test show the vertical dispersion and can show some of the accuracy potential without a chronograph.

 

[SJB358]

For me it’s finding the charge that’s happy with a certain bullet weight. My neck tension may help since I do use a lot of bushing dies or Mandrels to keep that consistent. Also great brass helps a lot since it is consistent from shot to shot. Certain powders really shine in certain cases as well so it pays to have a back up.

I think single digit SD and under 15-20 ES is attainable with some diligent time. Doesn’t always guarantee accurate loads but it’s the basis of one in my opinion.

 

[hunter24605]

I tend to think that every step in the process from decapping to crimping and everything in between has the potential to effect it. The biggies, IMHO, would be neck tension, case length, OAL, and brass consistency.

 

[RL338]

The combustion process has to be as consistent as possible and result should follow.

 

[Idaho53]

All great feedback! This is an expensive thing to chase, thanks to chronographs I caught the low ES/SD bug and tested many of my loads for fun. Tested many rifles with existing loads that all shot under 1/2 MOA on paper (100 to 300 yards paper targets). Each rifle has handholds with top tier brass, consistent neck tension (all brass annealed and neck sized), match grade primers, top tier high BC bullets and Shilen barrels. The tests of each rifle/load combo. showed that seating depth made the most difference with lowering ES/SD, and I was able get each rifle/load to shoot in the single digits. What I learned is that the closer the bullets were to the rifling, the lower the ES/SD became...due to the initial pressure spike that helped with consistent powder burn down the tube. I also learned that lower ES/SD doesn't always correlate to better accuracy, especially inside of 500 yards. Since then I have been shooting targets at 1000+ yards and do see more of an accuracy benefit at these longer ranges with lower ES/SD....mainly vertical stringing but also see the velocity changes show up when there is some wind.

 

[JMRhino]

All great feedback! This is an expensive thing to chase, thanks to chronographs I caught the low ES/SD bug and tested many of my loads for fun. Tested many rifles with existing loads that all shot under 1/2 MOA on paper (100 to 300 yards paper targets). Each rifle has handholds with top tier brass, consistent neck tension (all brass annealed and neck sized), match grade primers, top tier high BC bullets and Shilen barrels. The tests of each rifle/load combo. showed that seating depth made the most difference with lowering ES/SD, and I was able get each rifle/load to shoot in the single digits. What I learned is that the closer the bullets were to the rifling, the lower the ES/SD became...due to the initial pressure spike that helped with consistent powder burn down the tube. I also learned that lower ES/SD doesn't always correlate to better accuracy, especially inside of 500 yards. Since then I have been shooting targets at 1000+ yards and do see more of an accuracy benefit at these longer ranges with lower ES/SD....mainly vertical stringing but also see the velocity changes show up when there is some wind.

I wonder if this supports the theory of using a neck crimping die, such as the Lee Factory crimp die, to promote consistent, concentric neck tension that leads to more consistent combustion? I try to really focus on all of the reloading steps and have achieved some incredibly low ES/SD numbers, but repeatability seems to be elusive... I appreciate everyone's feedback.