Puzzling Chronograph Results

[HTSmith]

So I used the club's Labradar today for the first time while developing a load for a 6BR with 80 Gr Bergers. My first load was 32.6 Gr of Varget--ES was bad and the group was bad. Second load was 32.8 Gr of Varget--ES was very good (7) but group was still bad. Third load was 33.0 Gr of Varget--ES was bad (29) but the group was a ragged hole! So the group with the worst variation shot the smallest group by a long shot. Not what I expected. How does this work?

(BTW the Labradar was a pleasure to use)

 

[lawrence97]

What matters is how it shoots at the distance you intend to shoot at. The chrono is a tool to help but not the deciding factor for what the gun wants to shoot.

 

[retired]

if you always shoot at the same place, at the same distance, same temp and humidity, you have found your load.
since that probably is not how life is, record your data and try again.
if you can duplicate it, then you want to see what it does at what your normal distance is. will it one hole way out there.

What matters is how it shoots at the distance you intend to shoot at. The chrono is a tool to help but not the deciding factor for what the gun wants to shoot.

 

[mike a]

I bought a $200 chrono awhile back. It often showed exactly the same velocity three or for shots in a row, or no velocity all all. I sent it back, bought more components and shot more groups. I've had good success with OCW tests and latter tests. Lately I've been thinking of getting a more expensive chrono. But WHY? Mike

 

[Dusty Stevens]

The chrono is like a borescope. Its a good toy to have but what matters is the target.

 

[338 Mollett]

The chrono is like a borescope. Its a good toy to have but what matters is the target.

+1

 

[Someoldguy]

I like bore scopes and chronographs.

I have never wished I had less information to make a decision with.

YMMV

 

[dkhunt14]

The thing about the chronograph is you can have the best ES numbers and if it isn't with the barrel timing, it can be the worst groups. Matt

 

[chop house]

I have never wished I had less information to make a decision with.

yep

 

[dellet]

I'll pose this more of a question than a statement. It is how I approach it, but would welcome thoughts or corrections.

My thinking is that the load with the lowest ES, is the best fill ratio, producing the most consistent burn rate, for the load combination.

The best group is the optimal velocity, or exit time of the bullet.

Keeping the load density of the 32.8 load to get the velocity of the 33 grain load. Basically what is happening by going to 33.2 and adjusting seating depth.

 

[ballisticdaddy]

I'll pose this more of a question than a statement. It is how I approach it, but would welcome thoughts or corrections.

My thinking is that the load with the lowest ES, is the best fill ratio, producing the most consistent burn rate, for the load combination.

The best group is the optimal velocity, or exit time of the bullet.

Keeping the load density of the 32.8 load to get the velocity of the 33 grain load. Basically what is happening by going to 33.2 and adjusting seating depth.

Like others have mentioned the chrono is a tool to help you but is not the deciding factor, the target is. Some of the lowest ES and SD numbers I have ran over the chrono did not group very well, listen to what the target is telling you as well as the chrono numbers.

 

[dsculley]

Information is good, information overload is bad. For information to be good, you have to be able to analyze it and come to a reasonable conclusion.

I have an optical chronograph. I know its limitations. I use it primarily for load workup to make sure I am not loading too hot. I watch the velocity increases as my load progresses to try to avoid over pressure issues. For the load that I pick to shoot, I will always defer to my target. If it shoots good at 100 yds, then I test it at longer ranges. If the load is shooting well at the extended ranges that I like to shoot, then it really doesn't matter what the chronograph said about the load. I have found it to be better to spend my time making sure my loading technique is consistent and then get trigger time than to spend more time chasing low ES/SD. By the way, if you do use the statistics from the chronograph SD is a much better predictor of the performance of the load than ES. ES can, and usually will, change every time you test the load. SD should remain fairly constant if you are testing enough rounds and assuming your reloading technique is consistent.

 

[dellet]

Adjusting seating depth for the best group is pretty common, but what is actually causing the change?

Are the changes due to jump, how the bullet enters the bore? Or is it fine tuning how the powder actually pushes it?

There's no doubt that burn rate changes with seating depth, so consistency of that rate should show up in measurable numbers of velocity. You should be able to predict with some bit of accuracy, cause and effect.

Jump, seemingly would be trial and error. How much of a running start produces the best produces the straightest entry?

This seems like a good use of the data collected with a chronograph.

 

[Dusty Stevens]

I've never been to a chronograph match. lets just say you go out and you get a load that has great chrono numbers I mean record setting stuff but it shoots a .750 group at 100yds (which is usually the case) but then you fiddle around a bit and then get one that shoots a .185 then another .195 back to back but the chrony numbers are junk- which one you gonna use? as a fellow competitor I hope you use the good chrono numbers load. and on the borescope- ive never seen a barrel shoot equal or better after borescoping. matter of fact I carry my borescope to matches and encourage everybody to take a look at their barrels. I'll even confirm your suspicions that your barrel is toast

 

[Someoldguy]

Using a chronograph to measure load velocity is something I much prefer to guessing. Likewise, I prefer to monitor my cleaning processes and bore condition with a bore scope as opposed to trying to 'read' patches.
Like most information, it can be misinterpreted.

User disgression is advised.

 

[suasponte]

I always shoot for a group at 100yds. If i get the bug hole I want then I chrono the load and put it on paper at longer distances (1000yds). Like most, the chronograph is a tool but the target tells the tale. ES with a good group is nice and what you want at LONG range. ES translates to vertical dispersion at 1000yds. The guy with the best vertical dispersion that can shoot on the water line usually will win. The scoring ring is the biggest at the water line thus allowing for a little more wiggle on the wind read.
Terry

 

[hikfromstik]

I was having wild numbers with a Howa 1500 until I started single feeding my rounds . The hollow points were hanging on the feed ramp and pushing my reloaded bullets in the case deeper . Ballistic tip bullets fed fine and had great SD's . I do believe if shooting long range with reloads a good chrono/magneto/doplar is a must have tool .