Standard Deviation (SD)

[bsumoba]

Also could have been the first shot of the day through a cold dirty barrel.
I have a theory on cold bore differential that is related to oxidization of the bore contents over the days/weeks since the last shot was fired.
Once you "wipe" the bore with a bullet and powder charge through the barrel, that oxidization gets nornalized again for the day's shooting session.

Firing a round the day before a match seems to really normalize my cold bore shots.
I now make a habit of stopping somewhere on the side of the road whenever I travel and letting loose a few rounds in conditions closer to my match location to check zero and gather hard dope whenever I can.

The tester stated that these were 10 rounds he had left while at the range, so it looks like he was already firing his rifle prior to the testing.

I have seen at times, the first shots for chronographing are just a little bit different, but not like the tester experiences. Maybe I'll see a 10-15 fps change from the norm, then it normalizes and my ES is usually around 8-16 fps afterwards. I wonder if the chronograph also needs time to "warm up"??? Just thinking out loud. lol

This is exactly what I do. I make up my ammo for the match and make extras and then go to the range the day before and shoot a few groups to get a good zero and get the velocities and spreads for that batch of ammo I just made. Then, it's ready to go for the next day. Last three steel matches I went to, I hit my cold bore shots which were out to 550 yards and 1-1.5 MOA targets at most.

[ar15barrels]

The tester stated that these were 10 rounds he had left while at the range, so it looks like he was already firing his rifle prior to the testing.

Did he state that he was ONLY shooting that gun at the range that day and only that batch of ammo?
It could have been 10 rounds left from a different batch.
Powder fouling can change how a barrel shoots until you wipe the barrel clean and lay down new powder fouling.
For example, maybe he was shooting reloader 15 all day and then shot 5 rounds through the barrel with varget.
That first round would certainly be suspect.
Then, the next day, he fired 5 more rounds for the 2nd test?

I have often brought multiple guns and only shot a few rounds through one of them in a day.

[bsumoba]

Did he state that he was ONLY shooting that gun at the range that day and only that batch of ammo?
It could have been 10 rounds left from a different batch.
Powder fouling can change how a barrel shoots until you wipe the barrel clean and lay down new powder fouling.
For example, maybe he was shooting reloader 15 all day and then shot 5 rounds through the barrel with varget.
That first round would certainly be suspect.
Then, the next day, he fired 5 more rounds for the 2nd test?

I have often brought multiple guns and only shot a few rounds through one of them in a day.

This is what he said, "Unfortunately I was at the end of my rounds I brought and only had 10 left to shoot . So I did two 5 shot strings starting each string with the same barrel temp and shooting each shot at the same intervals loading one shot at a time."

I too, have seen the use of different powders affecting the first one or two shots.

Many guys at the local range I frequent for 100 yard testing have seen me shoot 5-8 shots and then put it away, only to make them wonder what I am doing. I tell them I am trying to save barrel life...

[Metal God]

I had been shooting that same load through out the day . I'd already shot 40 of the same load . Also the 10 shots fired in the test were shots 105 through 115 of a well fouled barrel . I knew I did not want to do any of the testing from a cleaned barrel so I stared the day with the rifle already fouled .

Also could have been the first shot of the day through a cold dirty barrel.

Interestingly enough , The load that my scope is zeroed to ( not the load tested ) is dead on with a cold bore first shot . It still amazes me to this day how great the first shot is . The rest will dance around that shot in a sub moa group but the first one always seems to be dead center of POA . That's inside of 300yds , but still .

[LynnJr]

We are talking about chronograph velocity data.
Chronograph velocities and spreads do NOT determine group sizes on target.
Group sizes are determined by measuring bullet hole relative locations on target.

Yeah I should have said using a return to battery rest not a typical hunting rifle which is what this thread is about. On your typical lightgun your gun handling will often times invert your group. That never happens with a heavygun unless your rest system isn't working.

[bsumoba]

came back from the range to see if my dasher would agg good groups across multiple days and it looks good. 5-shot groups in the 1's and low 2's.

ES/SD looks good too. I always try to do 5 shots. Two weeks ago, I was getting ES was 4 and SD was 2.2. Today, ES of 8 and SD of 2.8

[LynnJr]

Most people don't use there chronograph properly to see how good there ammo actually is.
Leaving a round sitting in a hot chamber will raise the velocity over 100 fps and shooting your first round after cleaning and a cold bore will lower velocity 125 fps.
Bryan your all set.

[Wrangler John]

Very informative. All this time I thought standard deviation was stopping at the mistresses' house on the way home from the range.

[Rizzo]

In ladder testing, you load up 15-20 rounds TOTAL in very small powder charge increments to cover the whole charge RANGE from minimum to maximum.
Then, you setup a target at 300-400 yards and fire the whole string from lightest to heaviest, stopping after each shot to label the individual bullet holes on the target.
What you will find is that there will be a definite range where several rounds are very close in the vertical "climbing the ladder" compared to all the other shots which will have wider spacing on target between shots.



That tight sweet spot is where you want to be as it will give you the smallest groups at longrange.
You can also chronograph during ladder testing as well as look for pressure signs on each charge level.
That's usually how you know to STOP firing the ladder test.

Randall,
I've been thinking about your explanation of what Ladder Testing is and was thinking that shooting one cartridge with a minimum load, then another with a small increment powder increase, etc., etc., as you mentioned could be misleading.
That is, one or more shots could be a "flyer" and give you a wrong interpretation of the ladder test node you are looking for.

Some shoot 3, 5, 10 shot groups rather than just one shot to circumvent the possibility of a flyer in that one shot test.

When shooting 10 shot groups of the same powder charge, there is a spread between the shots on the target, and sometines a flyer as well.
But, shooting additional groups with small increases in powder would give a better "picture" of which charge is the most accurate.

Do you shoot multiple tests and then compare the targets for consistency so you can then determine where the "node" is?

Perhaps I am missing something here in my understanding.

[ar15barrels]

Standard Deviation (SD)

Custom barrels shoot so much more accurately that flyers are always caused by the shooter.
The goal of ladder testing is to find the node (which will usually be 3-4 rounds) with fewer rounds down the barrel.
It's OK if there is a flyer.
The pattern will still be evident.

It should be noted that 100yd group shooting is of very little use when seeking a load with lower horizontal dispersion at long range.
A long range ladder test is by-far the easiest method.
I have done several 600 and 800yd ladder tests as they get easier to read the further away you do them.
Two ladder tests with matching results assures that you are in the right spot.

[Rizzo]

Custom barrels shoot so much more accurately that flyers are always caused by the shooter.
The goal of ladder testing is to find the node (which will usually be 3-4 rounds) with fewer rounds down the barrel.
It's OK if there is a flyer.
The pattern will still be evident.

It should be noted that 100yd group shooting is of very little use when seeking a load with lower horizontal dispersion at long range.
A long range ladder test is by-far the easiest method.
I have done several 600 and 800yd ladder tests as they get easier to read the further away you do them.
Two ladder tests with matching results assures that you are in the right spot.

OK,...got it.
Thanks again for your input

[blockfort]

OK,...got it.
Thanks again for your input

Sorry to re-visit all of this, but some people who were saying ES was the most important and SD was useless. Do they feel that way just about velocities, or about POI/target analysis as well?

Sent from my SM-G920V using Tapatalk

[LynnJr]

If you have a accurate rifle in a good rest the Extreme Spread of your velocity will be the widest two shots on your target.
The guys who think Standard Deviation is the way to reload will call all there bad ammo fliers but if they checked it across a chronograph they would change there minds.

Also if you shoot 95 shots with a SD of 1 and you then shoot shots 96-99 incrementally spaced at 20 second intervals then let round 100 sit in your chamber for 90 seconds the velocity will go through the roof and your group will be toast.
In this example throwing out the brass as being the culprit or calling the shot a flier would both be wrong. The SD would look very promising and wouldn't tell us where the problem was.
The extreme spread would.

[bsumoba]

Sorry to re-visit all of this, but some people who were saying ES was the most important and SD was useless. Do they feel that way just about velocities, or about POI/target analysis as well?

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If the gun is shooting great groups and producing ES in the single digits, up to say 15, is all you can really ask for. You can chase your tail trying to get it down more. There is the saying that you can spend thousands of dollars getting your groups down to the 1's and low 2's. There is some truth to that. For me, the main processes that I felt lowered my ES/SD is: understanding of barrel harmonics and how to "tune" a load to the barrel, consistent neck tension stemming from annealing and proper brass prep techniques, same lot # powder and primers, good bullets that are vetted by shooting small groups at short distances and good vertical at longer distances, and powder weighing to the 0.02gr tolerance (1 kernel).

Smaller calibers should shoot lower ES/SD in general. Larger calibers by nature will exhibit larger ES/SD relative to smaller calibers.

Because I am a F-Class shooter, my main concern is vertical at long distances, so when shooting groups at short distance during my load development for a new barrel, I pay attention to my vertical dispersion. As I shoot the various charge weights, I am looking for flatter looking groups that hit about the same POI on the target over a range of powder charge. Horizontal dispersion is not as critical as I will typically tune it out with seating depth. Once I finish this process, I will then shoot it over a chrono and typically it will show good ES/SD. I will then shoot it at distance to see how well it shoots out to 1,000 yards and will shoot it over multiple conditions and days.

[blockfort]

If the gun is shooting great groups and producing ES in the single digits, up to say 15, is all you can really ask for. You can chase your tail trying to get it down more. There is the saying that you can spend thousands of dollars getting your groups down to the 1's and low 2's. There is some truth to that. For me, the main processes that I felt lowered my ES/SD is: understanding of barrel harmonics and how to "tune" a load to the barrel, consistent neck tension stemming from annealing and proper brass prep techniques, same lot # powder and primers, good bullets that are vetted by shooting small groups at short distances and good vertical at longer distances, and powder weighing to the 0.02gr tolerance (1 kernel).

Smaller calibers should shoot lower ES/SD in general. Larger calibers by nature will exhibit larger ES/SD relative to smaller calibers.

Because I am a F-Class shooter, my main concern is vertical at long distances, so when shooting groups at short distance during my load development for a new barrel, I pay attention to my vertical dispersion. As I shoot the various charge weights, I am looking for flatter looking groups that hit about the same POI on the target over a range of powder charge. Horizontal dispersion is not as critical as I will typically tune it out with seating depth. Once I finish this process, I will then shoot it over a chrono and typically it will show good ES/SD. I will then shoot it at distance to see how well it shoots out to 1,000 yards and will shoot it over multiple conditions and days.

I was more wondering if you are more concerned about ES or SD when looking at your groups' points of impact, their shot placement on the target, not the velocities.