Reloading for lowest Standard Deviation

[steve123]

I have noticed a couple of the folks from the Big Sky country that many of us have respect for have vanished off this forum...
Lessons the value by some margin. IMO

CW

Maybe the Dasher shooters stole their awesome reloading and other winning insights and used it against them, lol.

Then those 6BRA's guys said, hey, what the heck were we thinking giving out all this hard to come by knowledge!

 

[Stanley basin]

One thing that has helped me is a suggestion from Bob Pastor at vipers bench. He chrono's 50 rounds at a time. Tosses the brass that exceed his desired ES in his chrono. I tried this and got great results. It worked faster than weighing individual brass. It was a great tip from him.

 

[Laurie]

The best load for ES and SD minimum may not produce best accuracy.

In fact it rarely does! Sometimes it's quite the reverse in fact. Years back I had an old Savage-Stevens 340 in .22 Hornet and it produced some staggeringly impressive small ESs allied to some staggeringly large 100 yard groups. (4 shots with the same MV ex five wasn't a rarity!)

Interestingly, (strangely even!) many of the most successful L-R BR shooters tell you their most successful 1,000 yard loads don't have outstandingly small ES/SD values. So, always put small groups before small SDs - nice if you can get both though.

In addition to Ned Ludd's list way back in post #3, I'm frequently struck during load development how it's not just these factors, but how one particular powder charge weight often produces an ES half that of the next lowest. Whether rerunning the tests two or three times would replicate the result, or just show it up as a random one-off, I wouldn't know and have never tried to find out.

 

[Laurie]

One thing that has helped me is a suggestion from Bob Pastor at vipers bench. He chrono's 50 rounds at a time. Tosses the brass that exceed his desired ES in his chrono. I tried this and got great results. It worked faster than weighing individual brass. It was a great tip from him.

Interesting! This reminds me of something I read years back about one of the USA's top sling shooters who bought Winchester 308W brass by the thousand and did minimal preparation beyond mouth chamfering and culling out those cases with obvious damage or manufacturing flaws. If he got a bad shot he couldn't explain, that case went back in the ammo box turned the other way round from the rest. On reloading it that case or its primer was marked and if it produced a second bad shot it was tossed on the range there and then and not taken home. Out of square case-head or 'banana case' with one side of the body thin-walled presumably

Apart from the technical issues I was impressed by anybody whose sling shooting 'hold' is so good that he knows when a flier is something other than shooter fault. Sadly I never achieved that skill or confidence level in my sling shooting days!

 

[Bart B.]

The reason velocity ES at zero or 1 can cause a lot of vertical stringing is their barrel time has a small spread. They won't all leave at the same angle to the LOS. In spite of the muzzle vertical axis vibration frequency being the same for every shot.

This is compounded when 2 or 3 people shooting the same stuff see over 80 fps spread in a given load's average muzzle velocity.

 

[Bart B.]

Apart from the technical issues I was impressed by anybody whose sling shooting 'hold' is so good that he knows when a flier is something other than shooter fault.

In stable conditions, a good shooter slung up in prone can call all shots inside a half MOA. If his stuff tests about a half MOA, he knows a shot striking more than a third MOA off call is typically not his fault; the conditions changed.

 

[Bart B.]

On reloading it that case or its primer was marked and if it produced a second bad shot it was tossed on the range there and then and not taken home. Out of square case-head or 'banana case' with one side of the body thin-walled presumably

One way to check case wall uniformity is if the pressure ring after first firing is uniform in height. If easily visible on one side but not on the other, toss it.

PS:
There are some who think the case body area showing no expansion was the part that rested on the chamber bottom when fired. They must never watched a totally flat car tire expand fully to very round with way too much air put in it.

 

[Depart123]

One way to check case wall uniformity is if the pressure ring after first firing is uniform in height. If easily visible on one side but not on the other, toss it.
View attachment 1088722
PS:
There are some who think the case body area showing no expansion was the part that rested on the chamber bottom when fired. They must never watched a totally flat car tire expand fully to very round with way too much air put in it.

THAT is some great info I've never heard before. I'll be experimenting with that immediately.

 

[Bart B.]

There is a cheap, simple yet precise way to measure case heads being out of square.

Stand the case head into the corner if a square on a smooth table then spin it. If the case mouth appears to stay in place, the case head is squared up enough.

 

[Gappmast]

One way to check case wall uniformity is if the pressure ring after first firing is uniform in height. If easily visible on one side but not on the other, toss it.
View attachment 1088722
PS:
There are some who think the case body area showing no expansion was the part that rested on the chamber bottom when fired. They must never watched a totally flat car tire expand fully to very round with way too much air put in it.

I agree Bart. The force of gravity is irrelevant when there is 50000 plus pounds of pressure on the inside of the case

 

[Mr.Knowit all]

I double weigh everything, ESPECIALLY subsonic loads. My ES has to be less than 15 fps. If I can not get that I will find another load and/or bullet.

 

[normmatzen]

No one has really said WHY you would want to load for low SD (or low ES ) .
I do a two step load characterization for each new barrel ( I shoot long range BR and sometimes 1000yd F Class). I know that there is no solid connection between Mv SD and accuracy, but here is my process;

First, I load 5 rounds per load with 5-6 loads stepped 1% with what I think will be the approximate load in the center. I shoot 5 shot groups in round robin style and record the Mv of each shot. This step is to find the longitudinal resonance. I take my data home and do a curve on EXCEL after determining Avg. of each load group as well as ES of each load group. Then I do a curve fit for 4th or 5th order polynomial to find the lowest point on the ES vs MV curve. Ironically, after doing this, I have tried adjusting jump ( I start with 0.020 for convenience) and I have NEVER been able to improve on the load vs MV by changing jump. My theory is that tuning with jump just fine tunes Case volume. Instead I trim load weight with my curve fitting. I do this at any convenient range as I am just collecting Mv data, not group accuracy.
This first step means all your further steps (for the load just determined) will have very good SD (ES).

Second I shoot at the range I will be shooting ( 600 or 1000 yd) and tune my tuner for best group/vertical dispersion. I shoot 3-4 shot groups for each tuner setting . These loads are, for 3 shots,
one nominal load (from step 1 and one shot 1% high and bullet painted red with magic marker and one load 1% low and marked green. If I shoot 4 shot groups, 2 are 1% hi and 2 1 % low. By doing this carefully, you can control the actual shape of the group. You can tell if you have positive compensation if the red and green dusting on the target holes are at even height or even flipped.
This step tunes for the cantilever resonance. And, you will still have good SD (ES).

 

[Scott_B]

Shooting in a perfect controlled lab of sorts:
https://precisionrifleblog.com/2013...-warehouse-lessons-in-extreme-rifle-accuracy/