Use lowest SD or lowest MOA?

[Dusty Stevens]

If that's the case..than why does everyone strive for single digit ES/SD numbers?

I guess they shoot in chronograph matches. Online is the only place it matters it seems

 

[HIC3540]

Maintaining uniformity is my goal. The bullet seater I use for the 6.5 achieves the concentricity I expected, but the seating depths vary too much, in my mind. What are your thoughts on the Wilson seater w/micrometer to help get to the seating consistency? Hypothetically, all other variables staying the same on the above results, would .005" accuracy in seating depth improve ES/SD for 1000 yard shooting?

I use the Wilson seater/arbor press setup and although slow it is consistent. You will still see issues if your neck tension is not consistent, just like with other setups.

 

[Forrest Mc]

Shoot for ES/SD..and the groups with follow. If they don't than its human error or enviroment (wind, temperature) BTW..what distances that?

800, 900 ,1000

 

[coldboreshot]

Whoa, just finished reading this entire thread...once again, "borescopes and chronographs should come with psychological disclaimers".

 

[HIC3540]

Along the same lines as dmoran’s post, I first sort the lot of bullets base to ogive, then the loaded rounds base to ogive-on a well known Gunsmith’s recommendation. In effect you are looking for a difference in nose geometry as the Bob Green tool does. This is done after sorting the loaded rounds by seating pressure.

Before anyone speaks up with “I wouldn’t have enough matched rounds left for the target”, I don’t have that issue-I assume due to careful case preparation. For 50 rounds my seating pressure usually runs in a range from 20-24 PSI and the cartridge base to ogive varies no more than .0005” for 50 rounds which is how I sort them. This is a good lot of bullets.

This is a good callout on seating pressure. I have my force pack setup to transmit data directly to excel. I cull out rounds based on how far off the average I see an issue. The picture is just a random example of the data.

Dave.

 

[CharlieNC]

SD(target) = SD(velocity) * Harmonic Compensation(at range).
The SD of the shots on the target, and of muzzle velocity are directly measureable. Using a little math and ballistic calculator, the results from a ladder test can be utilized to quantify the harmonic cycle. Attempting to develop a load for velocity SD does not assure the harmonics and consequently target performance are in proper alignment, ultimately the target prevails as the foremost factor.

 

[SGK]

If that's the case..than why does everyone strive for single digit ES/SD numbers?

Because they are trying to load development at a short distance in order to reduce/eliminate atmospheric variables (wind) but have a load which ought to perform at longer distances?

Of course, if you could eliminate atmospheric conditions and develop loads in a tunnel you could follow Alex and just go for the smallest group at the longest distance you are going to shoot. If you (rightly in my view) dismiss the notion of convergence, absent human error the groups will always be smaller at shorter distances. But not many people have access to really long tunnels.

The other way is to say that a bullet's trajectory is defined the moment it has left the barrel. Ignoring atmospheric influences from round to round which we want to do, each bullet's path is set by its velocity and barrel harmonics at exit. The group produced by a series of rounds at 100 yards can be extrapolated to 200 and beyond. (Of course we hope also for low ES in bullet to bullet drag variance.) If it isn't good at 100 it isn't going to be any better at 200 and beyond.

So load development at shorter distances focuses on achieving the best possible mix of velocity ES/SD and POI ES/SD. One without the other isn't any good and trade-offs are necessary. No one is saying pursue low vel SD/ES in blind ignorance of POI ES/SD. But to look only at short range POI ES/SD without even knowing vel SD/ES is ignoring the fact that an optimal mix of both is required for longer distances. All else being equal, two groups at a 100 with equal POI ES/SD (same group size) but with different vel ES/SD aren't going to look the same at 200 and beyond. A tighter group at 100 with much worse vel SD/ES than another may well be a worse group at longer distances. It requires a good chrono which doesn't introduce significant measurement error.

In essence the debate is whether you believe convergence is possible. If not, develop at shorter distances to reduce atmospheric variables and work towards the best possible mix of both vel and POI ES/SD.

The rubber meets the road the moment the bullet exits the barrel. You aren't chasing after it and giving it a nudge every now and then.

 

[Sixgun]

800, 900 ,1000

http://forum.accurateshooter.com/attachments/15540698965884781032252514911870-jpg.1098470/ This is your 800, 900, 1000 yard target?

 

[rhovee]

The last few months I have had the opportunity to tune my hunting rifles at 1k on paper at Deep Creek. Didn’t have my chrono when finalizing load. After it shot small (3”) 3 shot group, then I set up my Labradar and checked it out. ES was 18-20 FPS and had very little vertical for a bipod and rear squeeze bag. The 338 edge shot a 1.25” 3 shot group and had an Es of 18. If I tune a rifle good, I can’t shoot the group small enough that the Es gives me a ton of vertical.

 

[Webster]

Hello all, I am trying to improve my new reloading skills and have been shooting lots of groups with various combinations looking for a solid 140 g. performer. I think I just shot the best I can do, but question whether to go with lowest SD group or best moa group.
Two days ago at the range testing the 6.5 CM with 5 shot groups,
Using a LabRadar, the best results I got were:
42.3 gr H4350 - ES 7, SD 2.6, avg 2807 fps, .39 moa
42.6 gr H4350 - ES 10, SD 3.8, avg 2821 fps, .32 moa

My gut tells me to go with the SD 2.6 load and work on distance to lands. I appreciate your input, thanks

Bud

If your shooting under 300 yards ES and SD don't mean much. Go for group size, that's what they measure for SR comp. I can shoot groups under .300" with a ES of 35 on my 6BR Varmint rifle.

 

[Forrest Mc]

http://forum.accurateshooter.com/attachments/15540698965884781032252514911870-jpg.1098470/ This is your 800, 900, 1000 yard target?

 

[Forrest Mc]

Oh, Lord no! The red targets are 104 yds. I had referred later to having shot a F-Class match which was 800, 900, 1000. That is what I thought you were asking about.

 

[Forrest Mc]

If your shooting under 300 yards ES and SD don't mean much. Go for group size, that's what they measure for SR comp. I can shoot groups under .300" with a ES of 35 on my 6BR Varmint rifle.

 

[Forrest Mc]

Yes, I was load developing at 100 yards, the only range available, to work up a load to take to my first long range (800-1000 yards) F-Class match. I think it was beneficial that the load I settled on was in the 3.8 SD range.

 

[CamTheBam]

All the match’s I shoot the smallest group wins. Never been to one where they measured SD..

What distance are you shooting?

 

[Dusty Stevens]

What distance are you shooting?

What distance does it matter on? Ive shot them all and never had to show chronograph numbers

 

[BenPerfected]

I guess they shoot in chronograph matches. Online is the only place it matters it seems

I would have to buy another chronograph as I gave mine away years ago. I do not measure FPS and only shoot one load and then make corrections with a tuner. What am I missing? Always thought the Lab Radar looked like a nice tool.
Ben

 

[tom]

99% of us are using consumer grade cronygraphs that may or may not be accurate. The holes in the paper ACTUALLY HAPPENED.

Tom

 

[Jennb]

Not in the real world. Ive never seen an impressive es/sd be close to the best load on paper where it matters.

You haven’t talked to or verified with enough top level, record holders then!

It may not matter in benchrest because there is less rifle contact but in F Class you can see it.

 

[Dusty Stevens]

You haven’t talked to or verified with enough top level, record holders then!

It may not matter in benchrest because there is less rifle contact but in F Class you can see it.

Im sure not going to argue that because my customers that hold records in f class are sponsored and on teams and im not at liberty to say but quite a few f class records stand by target results over chronograph results