Standard deviation FX Impact .30
- Thread starter marcella69
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I think, with the Impact, this would depend greatly on the amount of time the owner has spent fine tuning their other settings.
Every setting will effect another. So, someone shooting with factory settings will, most likely, have different results from someone who has fine tuned their settings. The regulator is a major player in SD, and in this equation, and its performance can be masked by the other settings.
That being said, I had outstanding SD's with my Impact. IIRC, The best I had was an SD of 1 while shooting .30's.
Cheers!
Tom
Every setting will effect another. So, someone shooting with factory settings will, most likely, have different results from someone who has fine tuned their settings. The regulator is a major player in SD, and in this equation, and its performance can be masked by the other settings.
That being said, I had outstanding SD's with my Impact. IIRC, The best I had was an SD of 1 while shooting .30's.
Cheers!
Tom
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I was getting an SD of 2.12 with my Daystate Pulsar .25 with its electronic regulator. If you're getting an SD of 1 with a mechanical regulator, I'd call the Vatican about sainthood, because you've just performed a miracle.
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It's all about the tuning and quality of the reg. This wasn't a common occurrence. As I said, It was the BEST I had.
I think somewhere in the 3's would be an above average SD for most rifles. 5's is very good. 7's good, and so on.
I think the heavy .30's are harder to move and take much more air to move, so they tend to slow everything down internally which helps it perform just that little bit better. Also, due to the cubic inches of air necessary to move that big pellet down that big tube, there is more leniency for small deviations without effecting the outcome. If you were to lengthen the barrel, you'd probably experience a drop in SD as well. That's the best I can figure anyway.
Tom
I think somewhere in the 3's would be an above average SD for most rifles. 5's is very good. 7's good, and so on.
I think the heavy .30's are harder to move and take much more air to move, so they tend to slow everything down internally which helps it perform just that little bit better. Also, due to the cubic inches of air necessary to move that big pellet down that big tube, there is more leniency for small deviations without effecting the outcome. If you were to lengthen the barrel, you'd probably experience a drop in SD as well. That's the best I can figure anyway.
Tom
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I was being facetious, Tominco; sorry about that . You have much more experience as I have only recently gotten into airgunning. I was getting an SD of 5.00 (76.38 ft-lbf)with the factory settings. This was based on a full bottle (250 bar to 150 bar, gun manometers) shot string of 40 shots regulated across a Chrony Master using JSB 44.75gr Diabolo Domed. I then destroyed my reg piston with the bonehead move of turning the adjusting screw against pressure. (I know, believe me; I've beaten myself up enough already over it :-(.) I got my Impact back from AOA yesterday after a reg rebuild. (Kevin tuned the reg pressure to 145.9 bar calibrated to boost power.) Now, I'm getting an SD of 6.89 (76.07 ft-lbf). I really expected better performance. However, this is based on JSB 50.15gr pellets. I don't know if my Impact just likes 44s better, or if I should be concerned. I will run another string in a few weeks. Thanks for your responses
. You have much more experience as I have only recently gotten into airgunning. I was getting an SD of 5.00 (76.38 ft-lbf)with the factory settings. This was based on a full bottle (250 bar to 150 bar, gun manometers) shot string of 40 shots regulated across a Chrony Master using JSB 44.75gr Diabolo Domed. I then destroyed my reg piston with the bonehead move of turning the adjusting screw against pressure. (I know, believe me; I've beaten myself up enough already over it :-(.) I got my Impact back from AOA yesterday after a reg rebuild. (Kevin tuned the reg pressure to 145.9 bar calibrated to boost power.) Now, I'm getting an SD of 6.89 (76.07 ft-lbf). I really expected better performance. However, this is based on JSB 50.15gr pellets. I don't know if my Impact just likes 44s better, or if I should be concerned. I will run another string in a few weeks. Thanks for your responses Upvote 0
Hi. Just out of interest do you use sorted pellet when tuning? I would have thought SD could be also
effected by the slight weight differences in the pellets.
I haven't done this myself but would think weighing and maybe sizing could bring the SD down.
I know for instance the Jsb .25 heavies had quite a lot of weight variation out of the tin.
I don't like the idea of just shooting my carefully sorted pellets through the crony to to see if it
has an influence but maybe I should. Hate sorting pellets .....
effected by the slight weight differences in the pellets.
I haven't done this myself but would think weighing and maybe sizing could bring the SD down.
I know for instance the Jsb .25 heavies had quite a lot of weight variation out of the tin.
I don't like the idea of just shooting my carefully sorted pellets through the crony to to see if it
has an influence but maybe I should. Hate sorting pellets .....
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Yeah, there's a lot of abbreviations, acronyms, and jargon in this airgun stuff. SD is short for standard deviation. It is a statistical metric that quantifies the amount of variation from the mean (average) in a set of data values. A low standard deviation indicates that the data points tend to be close to the mean of the set, while a high standard deviation indicates that the data points are spread out over a wider range of values.
SD is particularly important in ballistics because it is directly related to the reliable accuracy of a rifle or handgun. The lower the SD of a set of feet per second ("fps") data of a type of projectile, the more consistent the shot placement and therefore tighter, more accurate groups (less flyers). This is why a regulated gun is more accurate than a non-regulated gun, and why an electronically regulated gun is more accurate than a mechanically regulated gun; all else being equal.
Some chronographs will calculate SD. I use the Excel STDEV function after running a shot string over my Chrony.
SD is particularly important in ballistics because it is directly related to the reliable accuracy of a rifle or handgun. The lower the SD of a set of feet per second ("fps") data of a type of projectile, the more consistent the shot placement and therefore tighter, more accurate groups (less flyers). This is why a regulated gun is more accurate than a non-regulated gun, and why an electronically regulated gun is more accurate than a mechanically regulated gun; all else being equal.
Some chronographs will calculate SD. I use the Excel STDEV function after running a shot string over my Chrony.
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Yes, AirSupply; I'm sure sorting (and cleaning) pellets improves ballistics. Ted Bier of Ted's Holdover fame has some excellent videos on this subject matter: https://www.youtube.com/watch?v=fRN1Am8RBgs. I guess it's called for if you want to win Extreme Benchrest Pro Class like Ted did last year, but I am too lazy to do that stuff for hunting. I find my Impact is accurate enough without all that. That's what I love about airgunning; one can go as far down the rabbit hole as one wants! It is a vastly engrossing hobby.
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@marcella69 - I'd keep shooting it. A fresh regulator tends to need some time to settle in. Practice some other skill for a few hundred shots so that your not just wasting pellets down range. Consider making a small adjustment or two during this time. I couldn't say which parts and pieces need to settle in but, some regulators definitely improve over time. Sorry to hear about the mishap.
@airsupply - I would never use sorted pellets for tuning. Yes they can influence the numbers but, it's such a small influence that it's not worth worrying about it. At best, I might use a good tin of unsorted pellets for a final check on my tuning. If I were an olympic shooter, maybe this would change. Yesterday, I ran a 40 shot string for my Streamline which produced a 3.4 SD. I used the nastiest tin of pellets I've seen in a long time. I'd say 80-90% of the pellets have skirts that are badly bent.
Tom
@airsupply - I would never use sorted pellets for tuning. Yes they can influence the numbers but, it's such a small influence that it's not worth worrying about it. At best, I might use a good tin of unsorted pellets for a final check on my tuning. If I were an olympic shooter, maybe this would change. Yesterday, I ran a 40 shot string for my Streamline which produced a 3.4 SD. I used the nastiest tin of pellets I've seen in a long time. I'd say 80-90% of the pellets have skirts that are badly bent.
Tom
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That's freakin' awesome, BenSeagar! I am somewhat limited in my tuning options because I shoot 30 cal. @ MAX exclusively. I was getting 2.12 SD with my Daystate Pulsar .25, and a whopping 9.50 SD with my P-Rod (even with a sweet spot range) before that! So I guess the 6.89 SD with my current Impact is an OK tradeoff for the substantially higher power and the Smooth Twist barrel; I have pretty much doubled my power each time: 14.47 ft-lbf w/ the P-Rod, 41.53 ft-lbf w/ my Pulsar, and 76.07 ft-lbf with my new Impact.
My dream gun would be a 150 ft-lbf, electronically regulated rifle with a Smooth Twist barrel and a monster capacity high pressure bottle for high shot count! One can dream, can't one?
My dream gun would be a 150 ft-lbf, electronically regulated rifle with a Smooth Twist barrel and a monster capacity high pressure bottle for high shot count! One can dream, can't one?
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Thanks for the words of encouragement, Tominco; that's what I'm thinking (and hoping), too. I will hunt for the next couple weeks and then run another shot string. Thanks again
As far as the "mishap," I've learned more from my many failures than I ever have from my few successes! (You'd think I'd hit a tipping point eventually, but I continue to learn at an exponential rate!)
As far as the "mishap," I've learned more from my many failures than I ever have from my few successes! (You'd think I'd hit a tipping point eventually, but I continue to learn at an exponential rate!)
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