How do I get single digit ES/SD?
- Thread starter diegocn
- Start date
Lets say the chrony reads all rounds 100 fps low from the actually velocities, it will still give accurate ES/SD, but the average would be 100 fps low. Its not a compounding error.
If your measuring tape has 6" cut off and you measure two boards, one is 12' one is 13', you can still measure the 1' difference in length between the two, but your actual measurements will be 6" short.
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Mystic Precision
CGN Ultra frequent flyer
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- Summerland, BC
Trying to predict where the error in any measuring device will land is a fools errand. CHRONY had the error rating of their clocks in the product manual spec sheet... it is +/- X... so the ES is 2X this value. All optical chronographs run some level of error... magnetospeed and labradar TEND to have a small enough error to make their data a little more interesting BUT....
When the error built into a measuring device is at or larger then the values you are trying to calculate, that device is useless in helping you determine numbers of any use. Does it matter? as previously said, NOPE... cause the results on paper are not highly correlated to ES/SD to begin with. Why the current generation of shooters hate using targets is beyond me.... paper doesn't lie. And the further you put it away from the muzzle, the better the data will be.
YMMV
Jerry
you margin of error is plus minus a foot and a half, so what happens when you short board is 10.5 and your long board 14.5, you need more wood filler because your ES and SD margin of error huge.......cut you're wood by eye and when you're finished building, use your measuring tape to measure once to get an average for your dope card, a longer string will yield a better average to nail down your dope.........to many university drop outs trying to reinvent the world of shooting, what works on a computer doesn't work worth S$&T in the real world, but in the world of sales......someone sure is raking in the coin, guys are spending big money on cronographs and shooting way more working backwards faster because some salesman said.....do it this way...you'll save money....
I think you are making an assumption that the error is relative but consistently relative.
What if the error is simply random for every shot? In this case any round within 30 fps is inside the margin of error , and could actually have identical velocities...
The standard for inspection is to use something with an error that is 1/10th of the tolerance you hope to maintain.
Threads like this come up now and then, but nobody ever wants to hear about the realities scale variation from the same perspective.
The error with these simple IR based chronographs is largely based on consistent errors.
The clock rate will be +/- something. As long as the power supply is consistent, solid state devices like a clock won’t be so random. Might run a tiny bit slow, or a bit fast, but will remain fairly consistent. The distance between my old ProChrono sensors are unlikely to be exactly 12.00000000000” apart, like the math wants. Installation distance will vary, but not change shot to shot. The light sensors will have some varying ability to detect changes in light, but will largely be consistent with bullets of the same shape, in identical lighting conditions. Again, there will be a little slop, but is unlikely to vary from shot to shot, as long as the chrono isn’t under tree branches where lighting can vary shot to shot.
Then add on your shooting angle. If you aren’t exactly 100% parallel to the sensors, then the path of the bullet will be longer than 12.000000000000”. That messes up the math and it will read a lower reading. In practice, not a ton, but it will be wrong. Use the identical point of aim for testing a group and now you’re getting decent relative measurements.
To me, a chronograph is a tool to help find powder charge plateaus where I can be a little sloppy with charge weight and see minimal error on target, and also as a guideline for how consistent I can make my ammo.
I just started breaking in a new 6BR barrel and saw:
Shot 10-13 (same charge weight):
2716
2727
2741
2752
Cleaning and more shots at a higher charge weight. Ending with shots: 21-23:
2793
2791
2794
I don’t care at all about the absolute velocity, but with my labradar, it’s +/- just under 3fps here. My takeaway for now is that the barrel seems to have stopped speeding up and my reloading technique is fairly consistent. We’ll see what happens next range trip.
want to have fun? take 1 piece of brass and load it 12 times at the range, shoot it over the crony and see what the velocity spread can be over a single piece of brass with the same charge weight in it, if you can't get 1 piece of brass down to single digit ES and SD I don't know how you'd ever expect to get random pieces of brass to react the same as each other. so ladder testing to find a plateau in charge weight is hit and miss, was one shot really 30 fps faster? or was one 50 fps slower?
I guess if you ladder tested every piece of brass individually, you could sort your brass by the chronograph findings, then match the brass together that shoots the same speed and toss the weird ones
Thanks, this is exactly what Bryan Litz tests showed, the errors are not compounding. Maple57 and Mystic you guys always make for an entertaining thread!
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I wish I could load at the range. That would be fun!
I know Cortina and others use the pressure-sensing bullet seaters and sort based on that. I don’t have that, (and it bugs me, lol!) so you do bring up a point for all of us. Things can vary, sometimes beyond our control.
There is clearly a limit to this stuff, and like Jerry and others have said, the target is what matters. There are a variety of tools and processes we can use to get there.
Btw, elsewhere I posted a 200-yd ladder test for my .223, and a promising region on target was discovered earlier by finding a chrono plateau at a different rifle range at 100m. I had already shot many 0.3-0.4 moa 5-shot groups at 100m in that charge weight range.
I wish I could load at the range. That would be fun!
I know Cortina and others use the pressure-sensing bullet seaters and sort based on that. I don’t have that, (and it bugs me, lol!) so you do bring up a point for all of us. Things can vary, sometimes beyond our control.
There is clearly a limit to this stuff, and like Jerry and others have said, the target is what matters. There are a variety of tools and processes we can use to get there.
Btw, elsewhere I posted a 200-yd ladder test for my .223, and a promising region on target was discovered earlier by finding a chrono plateau at a different rifle range at 100m. I had already shot many 0.3-0.4 moa 5-shot groups at 100m in that charge weight range.
if you are using an arbor press, you can feel the pressure difference, the gauges just confirm what you are feeling, there are 3 seating pressure you need to be concerned about, easy, normal, and hard......easy and hard to into foulers, the rest go into the match box. interestingly enough, you can neck turn, anneal and everything else and the seating pressure will always vary, the only way to get it consistent is to back off on the neck tension, 1 thou is plenty more then enough and leave the inside of the necks dirty, the carbon acts as a lubricant when seating bullets. I clean my brass in an ultrasonic with a special recipe, it's shinier then steel pins. but then I use a make-up brush with a special powder on it to lubricate my necks and now I always get single ES and SD on my loads
They do.
Even though I use a labradar, I’m in agreement with Jerry, yodave and others that the pursuit of single-digit ES/SD isn’t a good use of my time. At the numbers I posted, the ES of the labradar is almost 6 fps. It seems goofy to aim for under 10 fps spread when the error is already about 6. So I just want the numbers to be grouped decent enough and like they say, look at the target for final confirmation.
Even then, it isn’t one target - it’s about shooting like that, on demand.
Anytime my ES is at the 15 mark, my rifle shoots very well. All I have is a Shooting Chrony beta. My last load work up, I use it for a safe load test. 1 round at each powder charge. Then only got the chronograph out to see what my finished OCW and OSD load would do. Then plugged the fps into my app, then tried that based on actual drop at distance.
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
Love to see your data vs group impacts on target at distance. 200yds is a start... 300yds is ideal.
Camera at target and just record your impacts... a camera at the shooting line to see the flags and downrange so you ensure you didn't miss a wind change vs impact on target.
If you have or access to a shotmarker, now you are playing with gas and will make this chore a ton easier.... plus you have downrange velocity (ever wanted a true BC for YOUR combo?)
Record the velocity numbers and let's say over 20rds...repeat for 2 to 3 rifles... be cool to see what you discover.
Jerry
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
If you use that 1 piece of special brass, you should have a ZERO velocity spread... and a group smaller then bullet diameter.
Jerry
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
Thanks for the info.
I’m using a beginner Lee press.
Too lasy... Lee collet neck die for me... works just fine. I will turn necks and typically run thinner then the herd... and anneal.
Jerry
I am a somewhat old feller and back in the day when I tried to play with the best “thin to win” was the saying. Of course we didn’t have the technology to understand ES/SD Then……
Same here, except for the part about always getting single ES and SD values.
I am making my way towards being portable to load at the range. Never thought about reloading a single piece of brass though. Interesting to try that. I picked up a gempro 300 from a fellow 'nutter that is battery powered and making a reloading road show of sorts would be a bit of an adventure. Roll your own at the range.. I have the Lee dippers to make it more old school. The annealing part between rounds would be problematic though! My stats are rusty but sample size of 5 is the minimum. 7 would make it legit from what I remember... I am no stats'pert by any means and I am sure those that have more experience will offer correction. Loading 7 might not be as daunting as it seems.
Same here Hammer. Use a magneto speed that I purchased from Jerry. It's those 5 shot groups on paper where shots 1 and 3 group together and 2,4,and 5 are relatively grouped but different location that comes up from time to time that I have trouble nailing down consistently. (not barrel warmth related shifts)
I have learned that paper talks.
Cheers!
Ronr
I have heard of folks reloading on the shooting bench while working up a load. Wilson dies and small reloading rigs like that make it a bit easier, and save having to try and mount your press to the club's bench.
With digital technology like most chronos, there is the chance that it works in increments of how far a bullet travels in its clock cycle, so watch out for all the results coming out at steps some number of feet-per-second apart. Hopefully it ticks fast enough that the steps are inches-per-second but you can still find quantum effects in the results if you're a mathematician.
With digital technology like most chronos, there is the chance that it works in increments of how far a bullet travels in its clock cycle, so watch out for all the results coming out at steps some number of feet-per-second apart. Hopefully it ticks fast enough that the steps are inches-per-second but you can still find quantum effects in the results if you're a mathematician.
