Question on SD. How many shot per group is sufficient?

[redrams9]

I have done a test much like what you guys are wondering about.
I owned a Magnetospeed V3 and when the Labradars first came out, decided to try it, as I was very interested in it's ease of use for multiple rifles and not having to switch pieces on and off barrels, and potential poi shifts etc.
Tried both in real time on the same loads and would sell the unit that i liked the least.
Over several range sessions with literally hundreds of rounds fired, the two units almost never varied more then 3-4 fps. I have been following this thread with great interest as I am obsessed with low SDs on my handholds, and I am not sure I completely agree that these units have that much variance and built in error?
For my 2 units to consistently run within 3-4 fps over 100s of rounds fired, suggests that they are much more precise then what has been stated.
These where only my two units and maybe there is variations between units? Or some units are not as accurate from factory or don't perform as well as others?
I am absolutely not disputing the fact based observations of some of the other great shooters on the thread here, and I know Jerry and have utmost respect for his views, and he has helped me over the years with advice and scopes, so we are clearly seeing that not all units may function in the same precision.
I have also tested my Labradar against a number of older chronos on the range, and they all seem WAY inconsistent from shot to shot, and I would not trust any of the older shoot-thru units in my experience.
The labrador can be a bit finicky about placement and other shooters muzzle blasts influencing the readings, so there is a bit of user knowledge to get the most out of it, but I do trust mine, maybe much more then i should lol?, but it seems to always be in alignment with what I am seeing on paper and in my ballistics, so I have come to lean on it heavily for load development.
I am super curious if anyone else has ran an informal test, like I did, between the two units in real time, and seen similar results?

 

[Alpheus]

Yes, I did. Varied between 2-8fps, Labradar reading was always a hair faster.
I put a lot of stock in my chrony, but the results on paper always have the final say. If one load has consistently less vertical but higher ES then another, I will go with that one.

I will be doing a lot of load development this weekend for my new rifle, so will be able to repeat this experiment.

 

[redrams9]

Interesting to see that we both saw very similar results, and it seems, even if we take the highest variance, 8 fps, on a 3000fps test load, that is a very small margin of error.

 

[BadAsMo]

If you find another shooter with a labradar, compare the values generated by both with the same shots.
That would be an interesting test.
Jerry

I do know another guy with one and we've been trying to get together at the range. Maybe now that the World F-Class match is over we will have more time.

 

[BadAsMo]

Yes, I did. Varied between 2-8fps, Labradar reading was always a hair faster.
I put a lot of stock in my chrony, but the results on paper always have the final say. If one load has consistently less vertical but higher ES then another, I will go with that one.

I will be doing a lot of load development this weekend for my new rifle, so will be able to repeat this experiment.

I hate to say this but I tend to believe the results of the Magneto a little more than the Labradar here. The reason I say this is the jump in speed is more incrementally linear in the speeds from the Magneto whereas the Labradar are a little less aligned with the powder charge increase.

I am slightly more interested on the downrange values from the Labradar though. It makes sense that the greater the measuring distance the more accurate the result. Since the Labradar can provide the speed values even at 100 yards, I'd like to draw those values into such a comparison to see if they seem more or less consistent.

 

[Mystic Precision]

I do know another guy with one and we've been trying to get together at the range. Maybe now that the World F-Class match is over we will have more time.

That would be a very cool test. Would the labradars interfere with each other?

Add a magnetospeed and a shoot through chronie and an electronic target... all sorts of numbers to crunch through

If get a chance to do a double labradar test, please let me know how it works out.

If someone gets one of Adams new 2 chronie set ups, love to hear how that works out. This could be very interesting technology.

Jerry

 

[Mystic Precision]

I have done a test much like what you guys are wondering about.
I owned a Magnetospeed V3 and when the Labradars first came out, decided to try it, as I was very interested in it's ease of use for multiple rifles and not having to switch pieces on and off barrels, and potential poi shifts etc.
Tried both in real time on the same loads and would sell the unit that i liked the least.
Over several range sessions with literally hundreds of rounds fired, the two units almost never varied more then 3-4 fps. I have been following this thread with great interest as I am obsessed with low SDs on my handholds, and I am not sure I completely agree that these units have that much variance and built in error?
For my 2 units to consistently run within 3-4 fps over 100s of rounds fired, suggests that they are much more precise then what has been stated.
These where only my two units and maybe there is variations between units? Or some units are not as accurate from factory or don't perform as well as others?
I am absolutely not disputing the fact based observations of some of the other great shooters on the thread here, and I know Jerry and have utmost respect for his views, and he has helped me over the years with advice and scopes, so we are clearly seeing that not all units may function in the same precision.
I have also tested my Labradar against a number of older chronos on the range, and they all seem WAY inconsistent from shot to shot, and I would not trust any of the older shoot-thru units in my experience.
The labrador can be a bit finicky about placement and other shooters muzzle blasts influencing the readings, so there is a bit of user knowledge to get the most out of it, but I do trust mine, maybe much more then i should lol?, but it seems to always be in alignment with what I am seeing on paper and in my ballistics, so I have come to lean on it heavily for load development.
I am super curious if anyone else has ran an informal test, like I did, between the two units in real time, and seen similar results?

Actually, this is within the error rating of the machines so they are working exactly as designed. Error rating is the range that MIGHT occur... not what WILL occur.

So a unit with a variation from 0 to max error is within spec and that can change with any and all shots. The relative consistency between the 2 machines is a great confidence builder that all is indeed well. And it would never hurt to test you gear against another machine from time to time to confirm things are working properly. I had a "bad" battery cause me all sorts of grief until I checked with another chronie and discovered my loads were working as expected... my chronie, not so much.

How far are you testing your loads?

Jerry

 

[Alpheus]

More data is always a good thing, right? :-D

I was shooting at a 100m berm, so not surprised it never picked up @ 100.
Don't worry about the actual values, was breaking in a new rifle.

 

[Ryan.M.Anderson]

I was out shooting on Friday and now realize that a 10 round sample is not sufficient. I ran 45 shots over the chrony and what was a 5 SD is a now 14.X SD. I am fairly confident that is a solid number now but will continue adding as I go out.

This has taught me two things.
1) Those social media posts of a magnetospeed with a SD of 5 and a sample size of 5 are pretty much useless.
2) An SD of 15 is actually pretty good for the type of shooting I do.

I am new shooting new brass and am guessing that some of my variance is neck tension stuff so I will probably run the rest of the brass over a mandrel to round out the necks to see if it helps.

 

[BadAsMo]

Would the labradars interfere with each other?
Jerry

The Labradar has a setting to make the signal channel of each unit unique so you can set up multiple units near each other and not pick up false readings from someone near you.
Basically the manufacturer did consider this as a design parameter, so that's good.

 

[Mystic Precision]

I was out shooting on Friday and now realize that a 10 round sample is not sufficient. I ran 45 shots over the chrony and what was a 5 SD is a now 14.X SD. I am fairly confident that is a solid number now but will continue adding as I go out.

This has taught me two things.
1) Those social media posts of a magnetospeed with a SD of 5 and a sample size of 5 are pretty much useless.
2) An SD of 15 is actually pretty good for the type of shooting I do.

I am new shooting new brass and am guessing that some of my variance is neck tension stuff so I will probably run the rest of the brass over a mandrel to round out the necks to see if it helps.

If you really want to do this SD/ES thing, only use fireformed brass. Some brass like Lapua need 2 to 3 firings to expand and settle to your chamber. Of course, neck tension matters and new brass is overly tight.. usually.

blah, blah, blah... you now see what I have been trying to tell you. Use the chronie to figure out your drop. Use the target to determine your tune.

How did the group look after shooting 10 rds?

Many F class shooters will shoot 17rds or 22rds based on their relay length, multiple times to stress their barrels to see how they behave. I have gone 30+rds to get them screaming hot due to locations I would be competing in. Groups were great... chronie data, meh....

Track your velocity vs shot number and see if there are any trends.

Jerry

 

[Mystic Precision]

The Labradar has a setting to make the signal channel of each unit unique so you can set up multiple units near each other and not pick up false readings from someone near you.
Basically the manufacturer did consider this as a design parameter, so that's good.

Look forward to your tests when you get a chance.

Jerry

 

[Ryan.M.Anderson]

If you really want to do this SD/ES thing, only use fireformed brass. Some brass like Lapua need 2 to 3 firings to expand and settle to your chamber. Of course, neck tension matters and new brass is overly tight.. usually.

blah, blah, blah... you now see what I have trying to tell you. Use the chronie to figure out your drop. Use the target to determine your tune.

How did the group look after shooting 10 rds?

Many F class shooters will shoot 17rds or 22rds based on their relay length, multiple times to stress their barrels to see how they behave. I have gone 30+rds to get them screaming hot due to locations I would be competing in. Groups were great... chronie data, meh....

Track your velocity vs shot number and see if there are any trends.

Jerry

It was a 1/2 minute 10 round group at 300M.

 

[BadAsMo]

When doing this sort of testing I like to use a target with a full grid of one inch targets. I fire one shot at each target in order. This way I can see any directional shifts over the shot string and hopefully identify certain predictable patterns. This is helpful for both string testing and ladder testing.

When doing a post mortem on a target like this and with supporting velocities from the chronograph I have found certain trueisms.

1) Barrel heat accumulation will lower the velocity over the shot string - I assume this is from thermal expansion increasing the bore diameter, but possibly because of a reduced temperature differential between the burning powder load and barrel/air in the hot barrel.

2) Copper fouling causes an increase in velocity and more consistent velocity. I believe this to affect the coefficient of friction between the copper jacket and the steel barrel. Copper to copper slides better than copper to steel. This is why the first few shots from a truly clean barrel are unpredictable and why a blow off period at the beginning of an F-Class match are so important. I also think this is why some guys just don't like to clean their barrels, or at least don't like to clean them well. While some shooters think you can accurately compensate for a POI shift from a truly clean barrel, I think that's pure juvenile BS... if the barrel is really clean and free of copper there is no precise predictability for the first 3 to 5 shots. Most barrels (even great ones) will walk at least a minute during these first 5 shots after a proper cleaning.

 

[Ganderite]

I have considered this myself and devised a test to prove or disprove the reliability, but I shot my chronogragh before I could do it.

Just line up 2 chronies in front of each other and shoot through both with each shot and compare the values.

The results would illustrate if there are inconsistencies from one shot to the next or if each chrony is consistent but off by ### fps.

Now that I have a Labradar I lost interest is running this test but maybe some CGNer out there could do it and post the results.

If there is a certain randomness between them, you could probably average the two for a statistically more correct value.

The chrony factory is not far from my range. 10 years ago mr. Chrony would come over to test his machines. He did this when he made a significant change in one of the components.

The test involved a plank that held 7 Chronys in a row. In the middle was an Ohler. The Ohler had the screens set farther apart than usual (double the distance) to increase accuracy.

He would shoot then with a 243, a 22, a 12 ga slug, a 308 and a compound bow.

He did this a number of occasions. What I noticed was that each Chrony would be X fps faster or slower than the Ohler. And this number was always the same, indicating a high clock speed on a Chrony and absolute accuracy. The error was in the order of 20 fps, one way or the other.

He posted a target down range to aim at. He said the Chrony was so accurate that small difference in the path the bullet took to cross the screens would add a variable to the range of velocities.

When he left, he left the Chronys behind.

As for using SD to develop a long range load, this is a silly idea. The load must be developed at long range. Excellent ammo does not produce excellent groups. Ammo that exits the muzzle at the right time and place produces excellent groups.

Ammo must be made to a high standard (consistent case weight, charge weight and neck tension) but the velocity has to be adjusted to match the barrel harmonics. The only way I know to do this is to test at long range.

Your profile does not show your location. If it did we might be able to suggest times and places to test at long range.

If you can't test, load 3 batches of ammo: Your best load and then another batch 0.4 gr milder and hotter, and try to sneak in a test at the range on match day.

Can you shoot the course of fire 3 times?

 

[Mystic Precision]

It was a 1/2 minute 10 round group at 300M.

Very good shooting indeed. Assume you were using typical foldy bipod and beer can type rear bag... not skipods and fancy rear bags?

As you have said, plenty good for the intended needs.... if you want to tweak things a bit, consider testing 0.1gr on either side of your ideal. Group WIDTH will not change but HEIGHT will. With quality barrels/rifle/etc, getting the vertical down to 1/4 MOA or lower is no big deal with a quality milligram scale.

I feel this really matters when you reach out further and get little feedback from your target. When all you get is a clang on a gong, it would really help to know that your vertical is super tight. That way if you see any splash you have confidence to adjust your come ups as needed.

The come ups of any set up can and will change with ambient conditions - F class shooters are on paper targets at fixed distances shot from similar spots. If there was ever a sport to set and forget, this is it BUT we still adjust our elevation through the day and through the weekend. Maybe not much, maybe quite a bit.

I have watched a bunch of PRS type videos and you can see the impacts on gongs high or low.... followed by a miss at a further target as the shooter assumes the past hits were centered and drops are working as hoped. But the reality is the come ups are off for that time of day and they are going to bleed points, not because they executed poorly but because the trajectory has changed and they don't have/didn't notice the feedback to account for that.

Maybe this helps, maybe it doesn't. For me, it is part of my load work up and testing. When I confirm against a good scope, I have alot of confidence in adjusting for varying distances. When a shot doesn't land center, I can trust something in the conditions is changing my impact and adjust accordingly... obviously, a good shot release is paramount but if you are shooting 1/2 MOA at 300yds, you have plenty of skill to get hits on 2 MOA gongs.

Hope this helps.... good luck at your next match.

Jerry

 

[Ganderite]

Chronograph Test

 

[BadAsMo]

I have watched a bunch of PRS type videos and you can see the impacts on gongs high or low.... followed by a miss at a further target as the shooter assumes the past hits were centered and drops are working as hoped. But the reality is the come ups are off for that time of day and they are going to bleed points, not because they executed poorly but because the trajectory has changed and they don't have/didn't notice the feedback to account for that.
Jerry

PRS shooting is a tough gig Jerry... Much more challenging than F-Class.

The worst mistake a guy could make is to underestimate the dedication of the competition.

It's physically demanding as you move through the course of fire. There are no wind flags and even if there was, you would not have the time to read them. Mirage is there but you are so focused on lining up the sights that you probably will not even notice, never mind interpret.

Parallax is a trick because you have to set it and run without the luxury of doing a head bobble to confirm static.

And you get one shot and change to another target without anyone showing you where the round hit. If you cannot call your shot, you are shooting blind with no feedback and the spotters will not generally tell you where you missed. There's no chasing a spotter in PRS.

Being great at F-Class is no assurance you will do well in PRS until you've learned certain lessons and adjusted to the realities of PRS.

 

[Ryan.M.Anderson]

Very good shooting indeed. Assume you were using typical foldy bipod and beer can type rear bag... not skipods and fancy rear bags?

As you have said, plenty good for the intended needs.... if you want to tweak things a bit, consider testing 0.1gr on either side of your ideal. Group WIDTH will not change but HEIGHT will. With quality barrels/rifle/etc, getting the vertical down to 1/4 MOA or lower is no big deal with a quality milligram scale.

I feel this really matters when you reach out further and get little feedback from your target. When all you get is a clang on a gong, it would really help to know that your vertical is super tight. That way if you see any splash you have confidence to adjust your come ups as needed.

The come ups of any set up can and will change with ambient conditions - F class shooters are on paper targets at fixed distances shot from similar spots. If there was ever a sport to set and forget, this is it BUT we still adjust our elevation through the day and through the weekend. Maybe not much, maybe quite a bit.

I have watched a bunch of PRS type videos and you can see the impacts on gongs high or low.... followed by a miss at a further target as the shooter assumes the past hits were centered and drops are working as hoped. But the reality is the come ups are off for that time of day and they are going to bleed points, not because they executed poorly but because the trajectory has changed and they don't have/didn't notice the feedback to account for that.

Maybe this helps, maybe it doesn't. For me, it is part of my load work up and testing. When I confirm against a good scope, I have alot of confidence in adjusting for varying distances. When a shot doesn't land center, I can trust something in the conditions is changing my impact and adjust accordingly... obviously, a good shot release is paramount but if you are shooting 1/2 MOA at 300yds, you have plenty of skill to get hits on 2 MOA gongs.

Hope this helps.... good luck at your next match.

Jerry

Yep, an Atlas and a rear bag, I was trying out a new rear bag that day (actually a really old bag that I was trying again).

This discussion has actually been very helpful overall though. Aside from load testing at 100M I rarely shoot paper anymore and shoot steel 90% of the time.

Due to our discussions I shot more groups at distance last week and think I will now shoot a bit more paper than I have in the past. I may or may not change my load development process but as you said banging a 2 MOA gong does not tell you a high or low impact whereas paper will.

 

[Ganderite]

PRS shooting is a tough gig Jerry... Much more challenging than F-Class.

The worst mistake a guy could make is to underestimate the dedication of the competition.

It's physically demanding as you move through the course of fire. There are no wind flags and even if there was, you would not have the time to read them. Mirage is there but you are so focused on lining up the sights that you probably will not even notice, never mind interpret.

Parallax is a trick because you have to set it and run without the luxury of doing a head bobble to confirm static.

And you get one shot and change to another target without anyone showing you where the round hit. If you cannot call your shot, you are shooting blind with no feedback and the spotters will not generally tell you where you missed. There's no chasing a spotter in PRS.

Being great at F-Class is no assurance you will do well in PRS until you've learned certain lessons and adjusted to the realities of PRS.

Thank you for this. I have never shot this program or even seen it shot (on the range or on YouTube).

100 yard groups are just about useless, or even worse than useless.

The vertical group at 100 (which you will load develop to improve) might very well be the best load at 900 yards. I have not found any alternative to shooting long range for long range ammo development.