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Standard Deviation Question

GardDog

GardDog

LT
Full Member
Minuteman
Apr 16, 2009
2,200
1
52
New Orleans
#1
I have been reloading for target shooting / hunting for several years, with my only training coming from books and what I figured out from doing stuff the wrong way the first time. I have picked up a lot of great info from this forum and I have since refined my reloading process. I came upon this quandary after loading several different projectiles for my 300 WSM load development project. All of the cases were prepped with the same process, all of the powder was loaded with the same level of scrutiny, etc. All of the loads were with Win brass, 65 gr of H-414, Fed 215M, and set to 2.836”. The SD results were: 27.96, 6.04, 39.64 and 12.72. How is it that my Standard Deviation ranged from 6.04 to 39.64, even though the prep process was the same? Is it that different projectiles won’t give consistent results with the same powder? Also, the load with the SD of 6.04 was a 2” group….
 
#4
Re: Standard Deviation Question

What kind of chrono do you use? I have a Shooting Chrony and I don't trust it for crap. Its average speed on strings fits my field dope OK, but the extreme speeds and deviation stats don;t match what I see on paper.......
 
#5
Re: Standard Deviation Question

I have the Shooting Chrony Beta Master. I was just at a point where I don't know how I can get any more particular with my loading process and the results puzzled me.
 
#9
Re: Standard Deviation Question

Lower SDs are directly related to how you throw your powder and what primer you use. The more violent the primer the higher the SD numbers. Consistancy is the key word.

I have owned 2 Shooting Chronys. I sold the first and gave my older brother the other one. Now he uses mine. Look for a better unit. I have an OLD Pact that has been very good to me. Chronographs are one thing where you get what you pay for.
 
#10
Re: Standard Deviation Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JWP6114</div><div class="ubbcode-body">Never even checked my SD and i consistantly shoot sub .5 MOA at 100yds. </div></div>

Longer ranges (600 to 1000 yards) will eat you alive with high SD numbers.
 
#11
Re: Standard Deviation Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Victor N TN</div><div class="ubbcode-body">Lower SDs are directly related to how you throw your powder and what primer you use. The more violent the primer the higher the SD numbers. Consistancy is the key word. </div></div>

Can you expand on, "how you throw your powder"?

I'm using Fed 215M primers, are others associated with better performance long distance?
 
#12
Re: Standard Deviation Question

The primers are fine. How do you throw your powder charges? Do you thump...thump? Very quickly going to one stop then the other?

No matter what make powder measure you're using try this. Use your thumb and forefinger against the measure to stabilize your hand movements. For each and every powder charge move it in each direction taking 2 to 3 seconds per directional stroke. If it cuts a FEW kernals of powder go ahead and use that charge. If it grabs a whole bunch and everything binds up... put that charge back in the powder hopper. By moving very slowly in both directions and doing it at a consistant slow speed, you are letting the powder kernals align themselves better in the chamber of the powder measure and when dropping the cahrge the powder does the same thing in the case. Using this method can also help you get more powder in a case if you are using a compressed load.

Just for a FYI... This time of year we have very dry air inside the house. I made a 20 foot long ground wire out of small guage wire. 20 guage with aligator clips soldered on each end. I clip one end to the cold water pipe just around the corner on the washing machine. The other end I clip to the base of the powder measure. This helps a lot on static buildup. Static can cause a lot of powder to stick to your powder measure and not always drop into your cartridge case.

I hope these tips help out a little anyway.
 
#13
Re: Standard Deviation Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Victor N TN</div><div class="ubbcode-body">Just for a FYI... This time of year we have very dry air inside the house. I made a 20 foot long ground wire out of small guage wire. 20 guage with aligator clips soldered on each end. I clip one end to the cold water pipe just around the corner on the washing machine. The other end I clip to the base of the powder measure. This helps a lot on static buildup. Static can cause a lot of powder to stick to your powder measure and not always drop into your cartridge case.

I hope these tips help out a little anyway. </div></div>

My favorite anti static trick is to just wipe measure, funnel and anything podwer related with a dryer sheet (just wipe the outsides-static drops to nearly nothing). Also have your wife save them after they've been used in the dryer and throw them in with brass while tumbling-they catch alot of the dust.
 
#14
Re: Standard Deviation Question

I got away from the powder thrower and use an electronic scale and a pan funnel. Each load (I only do 20-30 at a sitting) is spooned out of the powder container into the pan funnel and measured to the 0.0. The pan funnel is poured into the case. It is slow going, but I'm trying for quality and not quantity.
 
#15
Re: Standard Deviation Question

I'm always open to discuss this type of thing if you want to PM me.

Have you checked the case mouths for carbon? Have you checked case necks for thick and thin spots? When prepping the brass did you uniform the primer pockets? Did you deburr the flashole?

I'm still considering the chrono unit itself.

Good luck.
 
#16
Re: Standard Deviation Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Victor N TN</div><div class="ubbcode-body">Just for a FYI... This time of year we have very dry air inside the house. I made a 20 foot long ground wire out of small guage wire. 20 guage with aligator clips soldered on each end. I clip one end to the cold water pipe just around the corner on the washing machine. The other end I clip to the base of the powder measure. This helps a lot on static buildup. Static can cause a lot of powder to stick to your powder measure and not always drop into your cartridge case.

I hope these tips help out a little anyway. </div></div>

Very interesting, I have noticed this (static) myself recently but wasn't sure why it had just started to happen. I will try some of the tricks you guys stated.
 
#17
Re: Standard Deviation Question

I have a shooting Chrony Beta Master and it does ok with me. I've been getting my SD's to stay in the 9.9fps range for the most part, and i've been happy with that. I'm not shooting for best rest or anything so i'm not expecting perfection, it does what I need it too.

I've read here and there that the chrony's are better if you have them in shade when shooting over them. Use the screens on blue sky days (per the instructions), but if you can get a fairly consistent setup, then you should get at least get consistently lousy readings (if that's the case anyhow).

Like I said, i've been happy with mine, but I don't expect top shelf chrono results from my $100 chrony.

Branden
 
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