Getting ES and SD down to single digits

[cajun]

A 168 vld with .618 bc at 3000 fps vs 3025 is 2.8" at 800 yds. VS 3050 fps is 5.5". So 25 fps is about 1/3 moa. 50 fps is about 3/4 moa.

 

[MagnumManiac]

My best ever improvement I made to my ES/SD dropping to single digits was to drop bushing dies.
I then bought Forster honed neck BR dies with custom expanders and a mandrel set.
I have also honed the necks on several RCBS dies and modified the expanders or made my own and have .002" movement within the die from sized to expanded.
I also use mandrels to get my final neck tension.
Experimentation is key, if you don't try different neck tensions you will never know what works or not.
My 32" F-class Open barrel in 300WM loves .0015" interference, my 28" barrel in the same cal loves .004".
My custom 25-06 loves .0025", my Rem Sendero 25-06 loves .001".
Reducing how much brass movement there is, is the biggest factor for me in reducing ES/SD numbers, BUT the results on target, regardless of what the chrony says rules.
I have a short course load in 25-06 with a 100g custom target bullet that puts 5 shots in the same hole @ 100……the ES on that load is right on an average of 100fps, go figure.

Cheers.

 

[Matt_C]

^^^ This and if it does not work try a primer change and sort and prep your brass very well neck tension can cause this also

And, if you do start changing things such as primers etc... do only one thing at a time. But as stated above, The shots on paper don't lie.

 

[WYOHTF]

I've learned again today
Thanks fellas

 

[WildRose]

I've learned again today
Thanks fellas

I've been here now over a decade and I promise, if you spend an hour reading here on various topics you'll learn at least one new thing or remember something you'd forgotten every day.

The only time we quit learning really is when we die or simply give up on living.

 

[Triple BB]

Good info here...

 

[JLDavid]

Ok update time. I had my brass annealed and trimmed them all to 2.025" after I sized them and made sure I had right at .003" shoulder bump. I removed the expander ball from my sizing die and expanded necks with a Wilson mandral in a seperate step. I turned the case necks to .0155" and noticed quite a variation in initial neck thickness. Also, I had a donut at the neck shoulder junction in quite a few of them. I loaded 21 cases and checked cbto dimension and made sure it was exactly the same as the load I shot half minute at 200 with. Still using WLR primers, 66.5 gr of 8133 and 168 moly Classic Hunters. I know I changed quite a few things but this will give me a pretty good baseline to see where I am with es and sd while putting bullets on paper at 300 yards. Will post my findings after I shoot this afternoon.

 

[QuietTexan]

I didn't ever see where you posted how many shots in the groups you were using to quantify SD and ES. There's a range of 5-10 shots that should minimize SD while stopping soon enough to keep ES from blowing up. That's where a lot of single-single statistical groups come from. Even the best-per-Litz 5fps SD loads will ultimately end up with double digit extreme spreads if you shoot enough of them. And conversely if you happen to shoot the two worst loads as your first two shots your SD can spike early. Or drop unreasonably low if you shoot two good ones.

So 5-10 shots per string for record if you want a single-single. Or all the shots if you want the truth.

The bit on the Engleman study in the source link below of creating sub-strings from one large 50-shot string and how the statistics are skewed inside a data set is very interesting, and a big reason why you should judge statistics against the target, and lean towards the target being more correct. Single digit ES is very unlikely in a high-confidence single digit SD data set, so don't let that crazy level of perfection be an impossible goal that stops you being happy with merely good statistics that result in great targets.

Source:

Muzzle Velocity Stats – Statistics for Shooters Part 2

Consistent muzzle velocity is key for long-range shooting, otherwise, bullets that leave the muzzle...

precisionrifleblog.com

 

[JLDavid]

Thanks for the information. Makes sense to me. Putting bullets on target will show me a lot. Whilr I want to have low es and sd, if I can maintain accuracy at distance with little vertical I will call it a successful day.

 

[JLDavid]

Just got back from shooting. The session was great and I got a lot of good info. My MV averaged 3064. My ES was 61 fps and my SD was 21. That being said, my accuracy held right at 1/2 MOA at 300 yards so my next move will be to take it to 400 and see if accracy holds. At this point, I am pretty happy with how it us shooting. The corrections from my rangefinder are nuts on to 500 yards. We shot steel after I put it on paper and my elevation was great holding center of steel. We did have a sneaky switching wind that messed with our windage/impacts a little. I need to get better are reading the wind. We did not shoot over flags but should have. I need to reaearch that.

 

[MOOSE39465]

Just got back from shooting. The session was great and I got a lot of good info. My MV averaged 3064. My ES was 61 fps and my SD was 21. That being said, my accuracy held at just under 1/2 MOA at 300 yards so my next move will be to take it to 400 and see if accracy holds. At this point, I am pretty happy with how it us shooting. The corrections from my rangefinder are nuts on to 500 yards. We shot steel after I put it on paper and my elevation was great holding center of steel. We did have a sneaky switching wind that messed with our windage/impacts a little. I need to get better are reading the wind. We did not shoot over flags but should have. I need to reaearch that.

I picked up a few pointers for his videos. Check them out,

 

[JLDavid]

I watched that video several times before I reworked my brass for this session. Lots of good info in it for sure. I really took my time while prepping the brass. Here are my 2 groups I fired at 300 yards before shooting steel. They aren't earthshattering but not bad for a hunting weight rifle and my not great skills!!! The 1st group was shot out of a cold clean barrel. The 2nd group was shot with shots 9-12. I fired 21 shots in all today.

 

[JLDavid]

I went and shot again today. 30° and full sun with just a hint of left to right breeze. I used fully prepped brass again but I did change to some old CCI 250 magnum primers. I dropped my charge weights some just in case I was going to be closer to pressure with the primer change. I loaded test loads of 65.9, 66.2, 66.5 and 66.8 grains of 8133. 65.9 and 66.2 shot even better than 66.5 did last session, well under .5MOA. Velocities for 65.9, 66.2 and 66.5 averaged 3055, 3060 and 3060 fps with ES of 21 and SD of 10. This is from a small sample so I am pretty sure I have not solved the ES/SD issues I was having unless I shoot a larger sample.

 

[JLDavid]

I shot again today. Conditions were great. 42° with full sun and a light breeze from 4 oclock position. I shot 2 5 shot groups at 300 yards with my 7mm and 8133 and CCI 250s. 66.2 shot the best again today. I had a really nice 3 shot group going and pushed the last 2 shots of course!!! It is definetly the shooter, not the gun. MOA correction is 1.75 minutes to 300 yards. I did not have to correct for wind and left my windage knob zeroed. The group ended up just under 1 MOA. Time to stretch it to 500 yards.