What is considered to be excessive shot spread;or, standard deviation? What are the possible symptoms?
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What is considered excessive shot spread;or, Deviation?
- Thread starter Nick47
- Start date
depends on the shooter
for me, more than 1 MOA is excessive, for general hunting purposes more than 2
Good is sub MOA accuracy
for me, more than 1 MOA is excessive, for general hunting purposes more than 2
Good is sub MOA accuracy
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The humorous redneck answer is: One Minute of Critter. Or, accurate enough to hit the brain/heart of the critter you are hunting. A deer has a larger vulnerable spot than a chipmunk. For paper plinking, less than 1 MOA is what I seek.
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Answers will be very subjective here. for me, being a FT shooter and plinker, ES on a target gun @ 10 fps for a hunting gun 20 - 25 fps.
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My understanding of standard deviation is the % of shots fired that will fall with in a certain range of fp/s.
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My bad edosan. I am referring to the velocity of the pellet. Not accuracy on target. In other words, the spread between the lowest velocity and the highest velocity.
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ahhh ok.. will depend: regulated or non regulated airgun? but at the end what matters is accuracy (and yes, there is a relation)
Anyway do not know the exact numbers, probably around 10fps on regulated airguns
Anyway do not know the exact numbers, probably around 10fps on regulated airguns
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I've seen rifles with an es of 20 fps shoot extremely well but generally regard 10 or below to be exceptional. I know there are plenty of examples in the 10 area by a lot of different manufacturers but not sure how the standard deviation over a large amount of shots are. Fairly certain that some yield small es figures for a single charge but may wander a bit over multiple strings. To me, day to day stability is more important than smallest es.
Bob
Bob
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I like to look at it in terms of the intended range. Something like 2% ES for 100 yards, 4% for 50 yards, or 8% for 25 yards. Generally with a well tuned regulated PCP and quality pellets, an ES of 1-2% is achievable which is actually better than target .22LR ammo.
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Let me further qualify what I said above... distance matters . At 20 yds , es of 50 or more may be unimportant. At 100, an es of as low as possible becomes somewhat more important .
Bob
Bob
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Agreed. This is why a 40fps ES with the new Ultimate Sporter I had didn't exactly help me out at 100yds.
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I think about 10 FPS max. is probably fine.
My stock .25 cal. Cricket has always chronographed 6-7 FPS max. spread every time I run 4 mags. through it.
But, 3 - 4 FPS is were almost all of them are. Seeing the chrony readout 4-up or 5- up is not uncommon during these strings.
That I believe is pretty amazing. Probably why it has always shot better than me. Especially at 150 - 200+ yards.
All my other (3 - regulated) guns are 10 - 15 FPS Max. spread. They do quite well too.
But, I've never shot them past a 100 yards on paper to confirm accuracy.
My stock .25 cal. Cricket has always chronographed 6-7 FPS max. spread every time I run 4 mags. through it.
But, 3 - 4 FPS is were almost all of them are. Seeing the chrony readout 4-up or 5- up is not uncommon during these strings.
That I believe is pretty amazing. Probably why it has always shot better than me. Especially at 150 - 200+ yards.
All my other (3 - regulated) guns are 10 - 15 FPS Max. spread. They do quite well too.
But, I've never shot them past a 100 yards on paper to confirm accuracy.
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Created: 01-18-2019 02:56:10 PM
Description: FX Crown. 25
Notes 1: JSB 25.39
Notes 2:
Distance to Chrono (FT): 3.00
Ballistic Coefficient: 0.036
Bullet Weight (gr): 25.390
Altitude (FT): 2000.0
Temp: 63 °F
BP: 27.89 inHG
Shots
# FPS FT-LBS PF
64 916 47.31 23.26
63 912 46.90 23.16
62 910 46.69 23.10
61 914 47.11 23.21
60 911 46.80 23.13
59 909 46.59 23.08
58 920 47.73 23.36
57 914 47.11 23.21
56 916 47.31 23.26
55 914 47.11 23.21
54 913 47.00 23.18
53 914 47.11 23.21
52 916 47.31 23.26
51 916 47.31 23.26
50 911 46.80 23.13
49 917 47.42 23.28
48 921 47.83 23.38
47 911 46.80 23.13
46 911 46.80 23.13
45 912 46.90 23.16
44 916 47.31 23.26
43 905 46.18 22.98
42 915 47.21 23.23
41 918 47.52 23.31
40 912 46.90 23.16
39 918 47.52 23.31
38 919 47.62 23.33
37 913 47.00 23.18
36 911 46.80 23.13
35 917 47.42 23.28
34 913 47.00 23.18
33 910 46.69 23.10
32 916 47.31 23.26
31 918 47.52 23.31
30 912 46.90 23.16
29 918 47.52 23.31
28 917 47.42 23.28
27 915 47.21 23.23
26 916 47.31 23.26
25 917 47.42 23.28
24 915 47.21 23.23
23 915 47.21 23.23
22 918 47.52 23.31
21 921 47.83 23.38
20 912 46.90 23.16
19 914 47.11 23.21
18 914 47.11 23.21
17 920 47.73 23.36
16 918 47.52 23.31
15 915 47.21 23.23
14 917 47.42 23.28
13 919 47.62 23.33
12 917 47.42 23.28
11 915 47.21 23.23
10 914 47.11 23.21
9 918 47.52 23.31
8 919 47.62 23.33
7 917 47.42 23.28
6 918 47.52 23.31
5 919 47.62 23.33
4 919 47.62 23.33
3 921 47.83 23.38
2 921 47.83 23.38
1 912 46.90 23.16
Average: 915.34
StdDev: 3.36
Min: 905
Max: 921
Spread: 16
True MV: 924.04
Shots/sec: 0.13
Group Size (IN): 0.00
how does this look? I’m under 2% but barely, should I try for better?
Description: FX Crown. 25
Notes 1: JSB 25.39
Notes 2:
Distance to Chrono (FT): 3.00
Ballistic Coefficient: 0.036
Bullet Weight (gr): 25.390
Altitude (FT): 2000.0
Temp: 63 °F
BP: 27.89 inHG
Shots
# FPS FT-LBS PF
64 916 47.31 23.26
63 912 46.90 23.16
62 910 46.69 23.10
61 914 47.11 23.21
60 911 46.80 23.13
59 909 46.59 23.08
58 920 47.73 23.36
57 914 47.11 23.21
56 916 47.31 23.26
55 914 47.11 23.21
54 913 47.00 23.18
53 914 47.11 23.21
52 916 47.31 23.26
51 916 47.31 23.26
50 911 46.80 23.13
49 917 47.42 23.28
48 921 47.83 23.38
47 911 46.80 23.13
46 911 46.80 23.13
45 912 46.90 23.16
44 916 47.31 23.26
43 905 46.18 22.98
42 915 47.21 23.23
41 918 47.52 23.31
40 912 46.90 23.16
39 918 47.52 23.31
38 919 47.62 23.33
37 913 47.00 23.18
36 911 46.80 23.13
35 917 47.42 23.28
34 913 47.00 23.18
33 910 46.69 23.10
32 916 47.31 23.26
31 918 47.52 23.31
30 912 46.90 23.16
29 918 47.52 23.31
28 917 47.42 23.28
27 915 47.21 23.23
26 916 47.31 23.26
25 917 47.42 23.28
24 915 47.21 23.23
23 915 47.21 23.23
22 918 47.52 23.31
21 921 47.83 23.38
20 912 46.90 23.16
19 914 47.11 23.21
18 914 47.11 23.21
17 920 47.73 23.36
16 918 47.52 23.31
15 915 47.21 23.23
14 917 47.42 23.28
13 919 47.62 23.33
12 917 47.42 23.28
11 915 47.21 23.23
10 914 47.11 23.21
9 918 47.52 23.31
8 919 47.62 23.33
7 917 47.42 23.28
6 918 47.52 23.31
5 919 47.62 23.33
4 919 47.62 23.33
3 921 47.83 23.38
2 921 47.83 23.38
1 912 46.90 23.16
Average: 915.34
StdDev: 3.36
Min: 905
Max: 921
Spread: 16
True MV: 924.04
Shots/sec: 0.13
Group Size (IN): 0.00
how does this look? I’m under 2% but barely, should I try for better?
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As a competitive FT shooter & tuner .... try my best to set up guns to hang at @ 1% velocity spread given equally consistent pellets to shoot.
That would be in a .177 at @ 900 fps staying +/- @ 5 fps
In a .20 cal at 800 fps +/- 4 fps
* However most times in the real world we're running 1 1/2 to 2% which is fine & realistically ideal for most serious FT competitors.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
AS TO THE high power STRING ABOVE ... Excellent being most larger caliber pellets don't size and weigh that consistent. KUDO's on a great tune IMO
Scott S
That would be in a .177 at @ 900 fps staying +/- @ 5 fps
In a .20 cal at 800 fps +/- 4 fps
* However most times in the real world we're running 1 1/2 to 2% which is fine & realistically ideal for most serious FT competitors.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
AS TO THE high power STRING ABOVE ... Excellent being most larger caliber pellets don't size and weigh that consistent. KUDO's on a great tune IMO
Scott S
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In my extensive fifty-yard accuracy testing of hundreds of airguns, I don't notice POI differences on shots falling within about 25 FPS extreme spreads. Even then I'd assign a (roughly) 1/4" POI difference at 50 yards to 25-30 FPS; meaning it takes a very accurate gun to differentiate such a small POI anomaly from the gun's grouping abilities. In my opinion it takes a gun capable of averaging 1/2" five-shot groups at 50 yards to identify a 1/4" flier with any high degree of confidence.
Mind you, most of my airgun accuracy testing for the last decade or so has been driven primarily by field-target competition accuracy concerns, and has (by necessity) neglected very high-dollar competition-specific airguns and optics, and tediously-sorted ammo. Nevertheless I believe this level of accuracy is adequate for most airgun purposes and shooters to 50 yards except serious bench-rest competitors.
A gun that consistently exhibits extreme spreads within about 25 FPS should also exhibit standard deviations within about 10; both well within the capabilities of most airgunners except top-level competitors.
Mind you, most of my airgun accuracy testing for the last decade or so has been driven primarily by field-target competition accuracy concerns, and has (by necessity) neglected very high-dollar competition-specific airguns and optics, and tediously-sorted ammo. Nevertheless I believe this level of accuracy is adequate for most airgun purposes and shooters to 50 yards except serious bench-rest competitors.
A gun that consistently exhibits extreme spreads within about 25 FPS should also exhibit standard deviations within about 10; both well within the capabilities of most airgunners except top-level competitors.
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I've noticed that my Crickets almost always do under a 10 FPS ES, both in .22 and .25. That's with pellets straight from the tin. Here's one that Ernest did on a .25 Cricket bull pup I had a couple of years ago after a tune, using .25 JSB 25.4 grain Kings. It says 9, but I'd call it 7 FPS, since it came off the reg. a shot prior to being called. I also did a 40 shot string with my .22 Cricket mini last weekend, and had a high of 869, low of 863 FPS (and only one 869). 250 bar fill, stock regulator, pellets direct from tin (JSB 18.1 grain).
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Gunny above has about a 1.7% spread (16 fps spread/915 fps avg). I suspect much of that variation is from the pellets, orientation of the barrel firing through the chrony, the breeze, and alignment of the stars and sun. It's extraordinary, especially for .25 cal. Best way to shrink it is to limit shooting to fewer shots, like stop at 42. Would've shrunk the spread to 10, or about 1%. Probably could pick a smaller string and done even better.
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