Acceptable Muzzle Velocity spread ?

Westside

Westside

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Hi Guys,

I have been slowly dialing on my .223 for long range. Stock Savage LRPV.

To date i have discovered that measuring the powder down to the nearest grain has quite a significant impact on my "round to round" consistency when shooting beyond 800 yards.

I was still getting a 30 fps variation in muzzle velocity so i switched over to federal match primers (gm205m). This afternoon i discovered that switching primers from winchester small rifle to the federal match was able to drop my variation in muzzel velocity down to 9 fps.

So my question for you all is how much further should i chase this rabbit down the hole ? (Is a 9 fps variance from round to round considered a good thing?)

I did shoot my best 100yd group to date as well.

TgtGfx.223.jpg
 
Test again at 200 to 300yds on a nice calm day. If the vertical continues to be less then 1/4 min, you are done

The error in the chronie clock is likely larger then the numbers you are trying to do stats on.

Holes in paper will give you all the info you need.

A chronie just lets you know if you are about to discover Entropy.

Jerry
 
Anything under an SD of 10 is more than acceptable for match ammo. 9 fps (if it is repeatable) is phenomenal.

My BR puts 15 rounds into an ES of 14fps with an SD of 4.
 
Thanks guys, its nice to know i'm on the right track.

Jerry the Forster seating die showed up today and it worked like a charm on the 80gr Berger VLD's so now i have another round to work up :D
 
You should be measurng your powders to the nearest 1/10th of a grain! a whole grain can make a big difference in a small case like a 223.

With that gun I think you'll rapidly reach a point of diminishing return to dig any deeper to reduce ES/SD numbers. Neck tension, brass sorting, run-out can call be checked, but judge the results, not the numbers.
 
CyaN1de said:
www.OnTargetCalc.com
Click to expand...

I just found this software the other day too and I won't be without it anymore! I recommend it to everyone. Very easy to use once you do your first couple groups. I take my phone to the range and snap a pic of my group and just tape over the same target until it requires replacement.
 
Obtunded said:
You should be measurng your powders to the nearest 1/10th of a grain! a whole grain can make a big difference in a small case like a 223.
Click to expand...

Pardon my typo, i am measuring my current load to within one stick of varget.

Each stick weighs .02 of a grain.

I am trying to weigh out each charge so that they weigh 25.80gr on the scale.

In actual fact based on the scale and the actual weight of each stick of varget i am assuming that i am still getting a variation of about .06 gr from round to round.
 
aletheuo said:
I just found this software the other day too and I won't be without it anymore! I recommend it to everyone. Very easy to use once you do your first couple groups. I take my phone to the range and snap a pic of my group and just tape over the same target until it requires replacement.
Click to expand...

CyaN1de said:
www.OnTargetCalc.com
Click to expand...


Hey thanks for the heads up this software...very easy to use.


Here is the groups from load dev on my 6bbr savage i am selling

TgtGfx.jpg
 
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Westside said:
Pardon my typo, i am measuring my current load to within one stick of varget.

Each stick weighs .02 of a grain.

I am trying to weigh out each charge so that they weigh 25.80gr on the scale.

In actual fact based on the scale and the actual weight of each stick of varget i am assuming that i am still getting a variation of about .06 gr from round to round.
Click to expand...

What type of scale is that. Have you tried removing and re-adding some powder to see if your measurement is repeatable? You might increase the accuracy of your measurement by mounting your scale to some stiff (concrete) structure that goes directly to the ground. A large glass bowl that will completely cover your scale as well as a temperature controlled environment will further increase the accuracy of your measurement.

But the experts (not me!) all agree that you're producing good ammo, so... is it worth it?
 
thebigslide said:
What type of scale is that. Have you tried removing and re-adding some powder to see if your measurement is repeatable?
Click to expand...

I currently have a My Weigh Gempro-250 Precision scale

Yes if i add/remove a single stick of varget the scale display goes up or down by .02 gr.

If you do some reading you will find that these type of scale are using some computing software to calculate the weight change or so i am lead to believe.

This scale was:
- the best bang for the buck
- available in canada
- meets my current needs
based on my research.
 
Westside said:
was able to drop my variation in muzzel velocity down to 9 fps.
Click to expand...

You are shooting very good groups.

What do you mean by a "9fps variation"?

One measure is "standard deviation", which a scientific calculator can calculate for you, as can many chronographs. For sample sizes of at least 10 shots, SDs of 20fps+ is pretty middling for match ammo (though you'll commonly see this on first-rate commercial match ammo e.g. Federal or Lapua), SDs of 15 are typical of "decently good" handloads and are capable of shooting to 1000 yards with little to no penalty, SDs of 10fps are truly first rate and capable of winning national matches, SDs of under 10fps are fantastic if you can get it but not always achievable.

Another measure is "Extreme Spread", which is the difference between the slowest and fastest shot in a string. Using a small number of shots (2, 3, 5) gives a pretty "noisy" measure as you might imagine. Using larger shot strings gives more useable results. You'll typically find that the Extreme Spread for a 10-shot group is roughly three times as big as that group's Standard Deviation. In may ways the ES for a 10-shot group can be used as a "poor man's substitute" for calculating the SD, for example an ES of 45 is comparable to an SD of about 15.

If you consistently have 9fps SD for 5 or more shots, you have first-rate ammo.

If you have ESs of 9fps for at least 5 but preferably 10 shots, you have astonishingly good ammo.


In either case, get out and shoot it at 1000yards.....!!!
 
rnbra-shooter said:
You are shooting very good groups.

What do you mean by a "9fps variation"?

One measure is "standard deviation", which a scientific calculator can calculate for you, as can many chronographs. For sample sizes of at least 10 shots, SDs of 20fps+ is pretty middling for match ammo (though you'll commonly see this on first-rate commercial match ammo e.g. Federal or Lapua), SDs of 15 are typical of "decently good" handloads and are capable of shooting to 1000 yards with little to no penalty, SDs of 10fps are truly first rate and capable of winning national matches, SDs of under 10fps are fantastic if you can get it but not always achievable.

Another measure is "Extreme Spread", which is the difference between the slowest and fastest shot in a string. Using a small number of shots (2, 3, 5) gives a pretty "noisy" measure as you might imagine. Using larger shot strings gives more useable results. You'll typically find that the Extreme Spread for a 10-shot group is roughly three times as big as that group's Standard Deviation. In may ways the ES for a 10-shot group can be used as a "poor man's substitute" for calculating the SD, for example an ES of 45 is comparable to an SD of about 15.

If you consistently have 9fps SD for 5 or more shots, you have first-rate ammo.

If you have ESs of 9fps for at least 5 but preferably 10 shots, you have astonishingly good ammo.


In either case, get out and shoot it at 1000yards.....!!!
Click to expand...

I shot a 5 shot string across my chronograph [shooting chrony]. I do realize that it isn't the best measuring tool but it helps me confirm that my reloading methods are bearing fruit.

5 shots with standard winchester primer
-3118
-3135
-3120
-3152
-3111

5 shots with Match primer
-3117
-3108
-3117
-Error
-3109

So based on my rough math i am getting a 9 fps variation with my best reloads.
 
Westside said:
I shot a 5 shot string across my chronograph [shooting chrony]. I do realize that it isn't the best measuring tool but it helps me confirm that my reloading methods are bearing fruit.
Click to expand...
A Shooting Chrony is a decent piece of gear and will usually give you good results if used carefully.

5 shots with standard winchester primer
-3118
-3135
-3120
-3152
-3111
Click to expand...
average = 3127, extreme spread = 41, standard deviation = 16.4

5 shots with Match primer
-3117
-3108
-3117
-Error
-3109
Click to expand...
average = 3113, extreme spread = 9, standard deviation = 4.9

In each case, firing more shots can only increase your extreme spread. The measured standard deviation might get bigger, it might get smaller, but with more shots fired it will come to be a more and more representative figure for that load.

Your load with the match primers will certainly show a larger Extreme Spread if you measure 10, 15 or 20 shots, however what you have is certainly a very promising start and definitely suggests that it would be worthwhile to shoot a longer test string at some point (either over a chrony or onto a target at 800+ yards, either way will tell you how your velocity uniformity is doing).
 
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