My latest Magnetospeed chrono test is depressing me. Usually I shoot 10 round tests. But it was suggested to me to run a whole box. Center-X had a 20.4 SD. SK Standard Plus (Yellow) was only slightly better at 19.3. Last week, a 10 round test of Center-X was 19.6 and the SK Standard Plus was under 5. It all is truly making me crazy!
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My SDs are depressing me.
- Thread starter AbbyKatt
- Start date
Y'er welcome. 
Typical lot testing at the Lapua facility is minimum of 40 rounds.
I require at least 50, preferably 100.
SD doesn't win competitions because ES is what loses them.
What will really mess with y'er mind,
run the tests with another box from the same brick
and watch the numbers shift.
It's rimfire, ya never know what y'er gonna get.
My current hobby is rimfire, 50 shots at 200 yards.
I've learned to figure ES from the vertical spread on target.
Typical lot testing at the Lapua facility is minimum of 40 rounds.
I require at least 50, preferably 100.
SD doesn't win competitions because ES is what loses them.
What will really mess with y'er mind,
run the tests with another box from the same brick
and watch the numbers shift.
It's rimfire, ya never know what y'er gonna get.
My current hobby is rimfire, 50 shots at 200 yards.
I've learned to figure ES from the vertical spread on target.
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Differences in muzzle velocity are not the only cause of vertical dispersion. Differences in muzzle velocity mean differences in energy released which means possibly significant differences in flexural barrel vibrations.
If there is variable wind, aerodynamic jump will be variable.
"...the very real and physical angular deflection of the trajectory which occurs when the just-fired rifle bullet first encounters the local atmosphere a few yards in front of the muzzle and is first exposed to the cross-track component of the horizontal wind (crosswind). "
"This effect was first discovered by precision shooting benchrest and across-the-course riflemen who noted repeatable vertical wind effects while firing in purely horizontal crosswinds."
https://www.researchgate.net/public...computing_the_wind-induced_jump_perturbations
Which are the most important? Have to do the calculations.
If there is variable wind, aerodynamic jump will be variable.
"...the very real and physical angular deflection of the trajectory which occurs when the just-fired rifle bullet first encounters the local atmosphere a few yards in front of the muzzle and is first exposed to the cross-track component of the horizontal wind (crosswind). "
"This effect was first discovered by precision shooting benchrest and across-the-course riflemen who noted repeatable vertical wind effects while firing in purely horizontal crosswinds."
https://www.researchgate.net/public...computing_the_wind-induced_jump_perturbations
Which are the most important? Have to do the calculations.
Don't overthink it. If its accurate at the ranges you plan to shoot it at, run with it.
Hold hard and favor center.
Hold hard and favor center.
Not sure where you live, but when I messed with 22LR, testing or even expecting a certain level of accuracy at distance under 45 degrees was futile. It was night and day from a warm summer afternoon.
I'd say those are pretty sad SD's for Center-X ammo. Apparently, you've got hold of a "bad batch". . . ??? For the two different lots of Center-X that I've been using, I've recorded 14 10round sets (that's 140 rounds all together) where with my Magnetospeed chrono I've recorded SD 's ranging from 3.0 to 9.8 and ES's for those ranged from 10 to 35 fps (the mean ES being 22 fps). While an SD of 20 is not particular "bad" for 22LR ammo, in general, it's sure not good for any high quality ammo. Hopefully, you don't have a large quantity of this Center-X and i'd bet your next purchase of it will do much better.
Though you got an SD of less than 5 for 10 rounds of SK Standard, one 10 round set doesn't really give you an a reliable idea of it's consistency. I'd say you'd need at LEAST 3 sets to get some idea of what you might expect from that particular lot of ammo. Same for the Center-X, though you've apparently already go 2 sets of it. Even with two sets at 20 for an SD, it wouldn't surprise me if you did a 3rd set and got something under 10. 22LR ammo and be very fickle this way.
Note: IMHO, ES's are indeed a more important number to take note of (as mentioned above posts), however, there is correlation between the two numbers and so I like to look at each for different reasons. For example, SD's give me a good idea about consistency of the ammo/loads and ES's for getting an idea of what I might expect for POI's.
We really need you to graph each of those 50 shots velocity to be able to help you. Also, a similar graph for the ES of each of the 50 shots. All must be in the order they were fired. I'm sure you sorted the ammo by rim thickness, if you're really serious, so please graph the rim thickness of rounds fired in the order they were fired. Once we overlay all those graphs and do extensive studies we should be able to pinpoint the cause of your issue.
PS it would also be invaluable to know the gross weight of each round also in order they were fired.
Please provide graphic display of weather conditions for, you guessed it, each of the 50 shots (yes in the order they were fired). This is most important to our study as we feel climate change is real and a clear and present danger to the effectiveness of the 22 rimfire cartridge.
Lastly, next time you test, please do not limit your testing to such a small test size. Fifty shots is just not a solid representative sample.
We look forward to receiving your data and providing you with solutions.
BAZINGA!
Hoser:
In one sense you are dead right. Any rational discussion has to start with an accuracy or precision goal. Then do what Bryan Litz calls a WEZ analysis, WEZ the acronym for Weapon Employment Zone. Terrible name. Should be Precision Factor Analysis or Accuracy Factor Analysis depending on whether precision or accuracy is your game. The idea is the determine the importance of each of the factors. Then only have to be concerned with those factors that are significant at level of accuracy or precision you want. Which is exactly why my game is shooting standing offhand. All the shit that degrades accuracy is immaterial in comparison to the degradation from my marksmanship. I can go to the range under calm conditions not worrying about the ammo, wind, nada but breathing, aiming, trigger pull and follow through. And hoping I do not have too many damn outliers.
On the other hand, if you game is to understand the causes of dispersion, you cannot overthink the situation. Understanding interior and exterior ballistics is not high school physics and chemistry. Done right you are doing ballistics research which requires both careful experimentation and analysis using very non-trivial math. If you do not do it right, the kind words would be numerical speculation and the unkind firearms blather.
A nice example of the effort is contained in link http://www.arcanamavens.com/LBSFiles/Shooting/Downloads/EnglemanChronographStatistics.pdf
although what he considers complicated equations are actually trivial.
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A final thought. The more you record at the range and the more you anal-yze the the data the closer to ballistics research and the farther from "shooting". Certainly not for everybody. However, if you are going to measure a lot of variables at the range consider analyzing the targets with the software On-Target TDS. www.ontargetshooting.com. Dirt cheep in scheme of things. If nothing else you can print many different types of targets from the software.
Attached shows target and information derived. Scanning and locating the bullet holes takes a couple of minutes. You may be able to locate the bullet holes more accurately than otherwise. Since I am very causal about sighting-in, just bench-bag-shoulder, I monitor the group offset from the aimpoint to determine if need to make any adjustments. Separating the dispersion into horizontal and vertical components is the real meat for comparing observation and theoretical prediction.
One aspect I have never tried is automatic aimpoint and hole recognition for targets with single shots per aimpoint. Have to use a On-Target target, but after recognition program does the statistics for all of the shots. How good is that?
I did not include one shot in the analysis because consider it a flyer, offset > 4.0" from AP, a unfortunate lapse in one or more aspects of my standing, offhand marksmanship.
Attached shows target and information derived. Scanning and locating the bullet holes takes a couple of minutes. You may be able to locate the bullet holes more accurately than otherwise. Since I am very causal about sighting-in, just bench-bag-shoulder, I monitor the group offset from the aimpoint to determine if need to make any adjustments. Separating the dispersion into horizontal and vertical components is the real meat for comparing observation and theoretical prediction.
One aspect I have never tried is automatic aimpoint and hole recognition for targets with single shots per aimpoint. Have to use a On-Target target, but after recognition program does the statistics for all of the shots. How good is that?
I did not include one shot in the analysis because consider it a flyer, offset > 4.0" from AP, a unfortunate lapse in one or more aspects of my standing, offhand marksmanship.
A quote from "Rifle Accuracy Facts". "We have found that small differences in the firmness of the hold can cause differences in vertical impact point." This statement was in context of bench rest shooting using firm-hold technique.
I have noticed that (sometimes) when I use a more 'free recoil' type technique, my groups are better.
Also, after a good barrel cleaning, my SDs with Center-X are now sub-10. I guess that not cleaning too often doesn't mean never!
AbbyKatt:
So many variables. The famous physicist Boltzmann said "There is nothing more practical than theory." Think of the testing needed to quantify the effect of all the variables. The only recourse if do not have a comprehensive theory. The one huge advantage of free recoil over firm hold is consistency. Consistency, consistency, consistency is a big name of the game.
Good shooting, Rick
Don't let the chrono depress you. I come from long range centerfire, I work up a accurate load, fire it at all ranges, then chrono for the speed. For rimfire, I shoot the ammo, find the most accurate ammo at all ranges, then check the speed. The high SD and ES is the nature of the rimfire beast. Shoot it and have fun.
Mark
I'm in the camp of cleaning a 22 just like and as often as I clean my centerfire rifles. I shoot various types of matches one of which is benchrest. Trying to shoot 75 perfect single shots on paper once a month shows me when my regular accuracy starts to change. For my Vudoo I see it around 500'ish rounds. It doesn't just turn to crap but it does start to throw an abnormal flyer here and there. The reason that I went to Vudoo was to get away from flyers being a normal occurrence. Anyway 1 wet and 2 dry patches and everything is back to rock solid. My flyers are probably just like your shot with an abnormal velocity change that was killing your ES.
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