NFOA MEMBERS FORUM
Ammunition & Hand Loading => Cartridge and Shotshell reloading => Topic started by: OnTheFly on June 13, 2013, 09:46:19 AM
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I am new to reloading, though I am working with a friend who has done a lot of reloading for precision rifle. We went to the range and chrono'd several different loads and found that we had a Standard Deviation (SD) of around 30. However, the accuracy out to 25 yards was, in my amateur opinion, very good. I was shooting off of a rest at a 6 (or maybe 8?) inch target and I grouped five rounds quite close. Of course "close" is considering the basic pistol sights, my ability to hold said sights in the same position, and my trigger pull. In the attached photo, the five shots are in a line at lower left from about the 7 to 8 o'clock position.
(http://i1120.photobucket.com/albums/l484/OnTheFly64/IMG_0938_zps983ea8f3.jpg) (http://s1120.photobucket.com/user/OnTheFly64/media/IMG_0938_zps983ea8f3.jpg.html)
My friend is used to seeing a much smaller SD, but logic seems to dictate that in a pistol caliber which is normally not shot beyond 25 yards, a larger SD is acceptable.
What say you pistol reloading experts? Is my logic sound? Edumacate me.
Fly
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Sounds about right to me. I shoot for single digit SD in rifles if I can, but for handguns I doubt it wod make much of a difference unless you're doing something like IHMSA silhouettes out to 200 meters.
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If ya aint got the pistol in a vice then there's just too much movement & play that can come into effect.
Compare all the ammo you load up with some factory and go from there.
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My reloading friend chrono'd some commercial ammo and he said the SD was much lower. Waiting to hear back from him on how low that number was.
Fly
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Reloading, shooting and statistics :o May I be excused, Mr Fly, my brain is full :laugh:
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A variance in muzzle velocity should have little or no effect on lateral [side-to-side] point of impact.
If velocity variance has any effect on POI at all, it will most likely show up in vertical POI variance. However, in the case of a handgun at 25 yards, POI variances due solely to velocity variances are probably not even measurable.
Some of the factors which affect variations in muzzle velocity are
variations in:
>primer brand [unless all ammo is loaded w/same primer batch]
>primer flash hole diameter
>cartridge case headstamps [different manufacturers]
>case cleaning
>bullet weights [weigh your bullets to 0.1gr and see what you find]
>bullet seating depth
>powder charge [unless each load is weighed to 0.1gr]
>bullet seating depth
>bullet crimping
>barrel warp under heating
It's almost impossible to separate the effect of these different variables on velocity variance.
Now, a 30ft/second SD for muzzle velocity means that the entire population of your shots experiences a variance range of 180ft/second.
Example: Assume standard distribution and an average MV of 1000ft/sec. Then the velocity range for all shots would be 910-1090ft/sec, with an occasional flyer above or below this range.
Which is a pretty hefty variation, but probably other factors [trigger pull, etc.] would have more effect on POI.
Final Analysis: The primary purpose of a handgun is personal protection. What shows on your target will work for you. Just fine.
sfg
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My reloading friend chrono'd some commercial ammo and he said the SD was much lower. Waiting to hear back from him on how low that number was.
Fly
I misspoke. He only looked at the data on commercial ammo.
Fly
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Reloading, shooting and statistics :o May I be excused, Mr Fly, my brain is full :laugh:
Ok...I must admit that I am a little bit of a CDO math geek. Maybe not as much as JTH, but more than most. ;D
Fly
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A variance in muzzle velocity should have little or no effect on lateral [side-to-side] point of impact.
If velocity variance has any effect on POI at all, it will most likely show up in vertical POI variance. However, in the case of a handgun at 25 yards, POI variances due solely to velocity variances are probably not even measurable.
Some of the factors which affect variations in muzzle velocity are
variations in:
>primer brand [unless all ammo is loaded w/same primer batch]
>primer flash hole diameter
>cartridge case headstamps [different manufacturers]
>case cleaning
>bullet weights [weigh your bullets to 0.1gr and see what you find]
>bullet seating depth
>powder charge [unless each load is weighed to 0.1gr]
>bullet seating depth
>bullet crimping
>barrel warp under heating
It's almost impossible to separate the effect of these different variables on velocity variance.
Now, a 30ft/second SD for muzzle velocity means that the entire population of your shots experiences a variance range of 180ft/second.
Example: Assume standard distribution and an average MV of 1000ft/sec. Then the velocity range for all shots would be 910-1090ft/sec, with an occasional flyer above or below this range.
Which is a pretty hefty variation, but probably other factors [trigger pull, etc.] would have more effect on POI.
Final Analysis: The primary purpose of a handgun is personal protection. What shows on your target will work for you. Just fine.
sfg
Thanks SFG. Very interesting information. Since you listed "bullet seating depth" twice, does that mean it has twice the effect as the other items you listed? ;)
Fly
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CDO
CDO???
(IF it's good then I'm that too, because I LOVE math and physics. Taught it through DiffEq at the college level for a decade. )
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CDO???
CDO = arranged how someone with OCD would 'spell' it...
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Fly:
Since you listed "bullet seating depth" twice, does that mean it has twice the effect as the other items you listed? )
Actually, it means that sometimes I don't do a thorough job of proofreading stuff before posting to the Forum.
sfg
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CDO = arranged how someone with OCD would 'spell' it...
NO!!!
It is the PROPER way to arrange the letters unless you are one of those people that just like to throw letters together without any acute organization or fanatical attention to detail. ;D
Fly
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Fly:
Actually, it means that sometimes I don't do a thorough job of proofreading stuff before posting to the Forum.
sfg
As an air traffic controller once said to me...It happens to the best of us, and you've just proven it.
Fly