OFtrash
Well-Known Member
Don't beat me up to bad. Im not completely new to reloading but have never really paid too much attention to ES and SD till getting into long range shooting. So my question is how much does powder choice affect ES and SD?
Powder choice vs ES and SD
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More experienced should chime in here but IMO it can. Of course every gun is different but in my experience in certain rifles powder choice did make a difference. As you go through load development and trying different things you should notice where all other things being equal (ie same bullet, seating depth, primer, brass) only changing powder that one will have better spreads than others. Much like when selecting charge weights. Hope this helps.
deadidarren
Well-Known Member
Well I only load one way that is I choose a powder that gives me good case fill without being too compressed for the speed that I'm after and depending on case size use a standard primer or a Magnum primer if it's slow burning powder in my 7 mm quite regularly get single-digit SD and very low double digit ES there are people out there who load better than me I am not exactly after every piece of speed that I can get but I do load to the top node .
I only use ADI (hodgden stick) powders as it's all that's available in Australia with any regularity .
I only use ADI (hodgden stick) powders as it's all that's available in Australia with any regularity .
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Es and Sd numbers are important, but not life threatening in the accuracy of a rifle. A lot of it comes down to how meticulous you are with your loading, accuracy of powder measured, seating depth, primer choice, brass is a big factor, and proper neck tension. Consistent neck tension is a big factor in ES and SD numbers. Single digit numbers are obtainable, but if you have an SD less than 20 you're fine shooting long range. Now if you're wanting to shoot bench rest, and shoot the smallest groups you can, then welcome to the black hole of reloading.
I've never had a powder that can't achieve good SDs, but I've had some that can't achieve a good SD at the velocity I want. Ball powders in particular tend to need high case fill to provide good velocity spread, which usually means near max charges.
OFtrash
Well-Known Member
I've done a lot CMP service rifle competitions so I have a fair amount of IMR 4895 that I used in my Garand and M1a and CFE 223 I used in the AR15. So Im trying to stick to what I have. I do not shoot as often as I use to due to mobility issues, so I'm kinda getting into shooting long range. Recently bought a Bergara B14 HMR in 308. Rifle seems to extremely accurate in load testing but I would like to see if I could get the ES and SD lower. The loads Ive worked up Im using IMR 4895 at 43.5 grains, 168 grain Nosler HPBT competition seated 15k off the lands, New Hornady Match brass with WLR primers. Average velocity 2,585, ES 44 and SD 15. These easily shoot around .75 to 1" MOA at hundred yards. Just wanting opinions on this load.
Thanks
Thanks
My biggest improvements in ES/SD has come from using better quality components and improving my reloading processes.
Think about temperature stable powders as well if you are serious about shooting long. You might be zeroed at a certain speed, with great accuracy, achieved at a giving temperature with great es/sd's. Now, with non-temperature stable powders, temperature changes, speed changes, zero changes, you miss. I suppose the largest factor is how big and far your targets are...
waveslayer
Well-Known Member
Industry Standard for reloading is SD's 10 and below. Even that it will affect your poi at distance
This!
Doom2
Well-Known Member
I don't know that any one powder is going to be intrinsically better than another but one of the main things that affects SD is the case fill. A case that is close to full is likely to have tighter SD than one less full so powder selection to get close to full is important. Conventional wisdom has been that single base extruded powders yielded smaller SD than spherical and ball powders. However that logic may not be the case today, or as significant a factor as it used to be.
Be careful when you go down the SD/ES rabbit hole. Many chase small standard deviations and look at small sample sizes. It is statistically unreliable to evaluate standard deviations with less than 20 samples. By definition the standard deviation does not fit a normal distribution like the mean (average). it is bounded by zero on the low side and it fits what is called a Chi-Squared distribution. To develop confidence in the standard deviation it takes a significant number of shots. When someone says they have a standard deviation of 8 fps that number has a confidence interval associated with it. For 3 shots that range is 4 to 50 fps. For 5 shots its 5 to 23 fps. For 10 shots 5.5 to 14.6, and for 20 shots it's 6 to 11.6 fps. If the reloader was looking for single digit standard deviation for his handholds he would be very unlikely to have it from the 3, 5, or even a 10 shot group. Even with the 20 shot group there is only a 75% confidence interval. This means that if an infinite number of 20 test were done 75% of them would be in the range of 6 to 10 fps.
Be careful when you go down the SD/ES rabbit hole. Many chase small standard deviations and look at small sample sizes. It is statistically unreliable to evaluate standard deviations with less than 20 samples. By definition the standard deviation does not fit a normal distribution like the mean (average). it is bounded by zero on the low side and it fits what is called a Chi-Squared distribution. To develop confidence in the standard deviation it takes a significant number of shots. When someone says they have a standard deviation of 8 fps that number has a confidence interval associated with it. For 3 shots that range is 4 to 50 fps. For 5 shots its 5 to 23 fps. For 10 shots 5.5 to 14.6, and for 20 shots it's 6 to 11.6 fps. If the reloader was looking for single digit standard deviation for his handholds he would be very unlikely to have it from the 3, 5, or even a 10 shot group. Even with the 20 shot group there is only a 75% confidence interval. This means that if an infinite number of 20 test were done 75% of them would be in the range of 6 to 10 fps.
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