ES question

[fr3db3ar]

I reload with Varget and weigh by hand down to the kernel. IE: I add or subtract one kernel of Varget to get my scale exactly on the line.

I have an ES of 30 on my .308 loads and 26 on my .223

Does anybody get any closer than that in their loading? Is 30 bad?

 

[fdshuster]

Not bad. I've recently chronographed some of my 6ppc & 6BR loads, and got ES's in the high teens and low 20's. The important question is, how do the loads group?

Sometimes a different primer, or a change in neck tension can make a small difference.

I personnally would not be concerned with those numbers in a 308 & 223, as long as the groups are acceptable. JMO

 

[jlow]

There are many variables that affect MV other than the powder.

So starting from the back, how consistent the powder is ignited will affect the pressure curve and thus MV, this could include the primer characteristics, the primer hole and whether there are burrs inside to deflect the flame from the primer. The volume consistency of the case, the seating depth of the bullet, the consistency of the shape of the bullet.

Neck tension also affects chamber pressure/MV which in turn is affected by the length of the neck, neck thickness consistency, how smooth the inside of the neck is, the ID of the neck, the bullet bearing surface length, the consistency of bullet diameter, etc and we have not even talked about the shape of ogive of the bullet and location relative to the lands in the barrel.

As many variables I can list, other can list many more…. ES of 30 is not bad but ideally ES is 10 or less if you are shooting long distance i.e. 600 plus yards.

Sorry, one mistake, I meant SDEV of 10 or less not ES.

 

[jhelmuth]

jlow is correct.... ES is a result of the total consistency for the cartridge (and not all factors are equal). So charge weight would be a fairly high factor. I think neck tension would be #2 (in my mind) - which would be more than just the neck size and runout as the brass elasticity would also be a part of that in total (so annealing becomes important). A close #3 would be case volume, followed by ignition (primer and flash hole) consistancy.

The more consistent you can be with the entrire loaded cartridge, the lower your ES is going to get. I don't achieve and ES of 10 very much, but 20 is doable... (over 20 rounds)

 

[jcampbellsmith]

ES only tells you the difference in velocity between your fastest and slowest shots, nothing else. No amount of hocus pocus can get ES to tell you anything more.

http://riflemansjournal.blogspot.co.uk/2010/07/statistics-for-rifle-shooters.html

Regards JCS

 

[fr3db3ar]

ES only tells you the difference in velocity between your fastest and slowest shots, nothing else. No amount of hocus pocus can get ES to tell you anything more.

http://riflemansjournal.blogspot.co.uk/2010/07/statistics-for-rifle-shooters.html

Regards JCS

I understand that but it leads to vertical stringing at distance. I'd like to keep it small but am unlikely to go to the extremes to get it.

Right now both loads shoot just over 3/4 MOA at 400 if I do my part.

 

[Jay Christopherson]

I'm usually much more concerned with standard deviation than I am with E.S.

I reload with Varget and weigh by hand down to the kernel. IE: I add or subtract one kernel of Varget to get my scale exactly on the line.

I have an ES of 30 on my .308 loads and 26 on my .223

Does anybody get any closer than that in their loading? Is 30 bad?

 

[jlow]

Yes, ES is the difference between the highest and lowest value. The reason that this number can be deceiving can be illustrated by the following example:

Lets just say you went out and shot 20 rounds and chrono them and half the rounds had an MV of 2700 fps and the other 2650 fps the ES for this string would be 50 fps and the SDEV would be 26 fps.

Now if you went out the next day with a load that you thought you had improved and shot another 20 rounds and now 19 rounds had an MV of 2700 fps but one round was 2650 fps. The ES for this string would still be 50 fps but the SDEV would be 11 fps.

You can see that if you only look only at ES, there was absolutely no change and so if you took this value as a way to judge if you made any improvement, you would conclude wrongly that there was absolutely no change. On the other hand the improvement is clearly visible if you look at SDEV which takes into account the degree of variability of the rounds plus its overall consistency. This is why SDEV is a more useful value to look at.

 

[dooley]

ES, is probably not relevant for hunters at distances less than 300yds but ES means more to long range target shooters, certain cartridges are easier to get low ES's, the 308 is not one off them, in approx 50 years of reloading I very seldom got ES's under 30 fps with this cartridge, on the other hand I have a 290 thou necked 260 Rem which very often gives me under 10 fps ES, which suprises me as I can never get ES's on my 6.5x47 lap that good, both have 30 inch heavy barrels, I would have expected to get lower ES's on the smaller cartridge, it seems the older I get the less I know. dooley UK

 

[mikecr]

fr3db3ar, what are your barrel lengths?

 

[joejo]

ES, is probably not relevant for hunters at distances less than 300yds but ES means more to long range target shooters, certain cartridges are easier to get low ES's, the 308 is not one off them, in approx 50 years of reloading I very seldom got ES's under 30 fps with this cartridge, on the other hand I have a 290 thou necked 260 Rem which very often gives me under 10 fps ES, which suprises me as I can never get ES's on my 6.5x47 lap that good, both have 30 inch heavy barrels, I would have expected to get lower ES's on the smaller cartridge, it seems the older I get the less I know. dooley UK

so what do you suppose the reason is? why should a 308 not shoot low es? i am just asking bc i shoot a 260 295 nk (on my second barrel; exactly the same) and have never been able to settle them down much. it can keep them in the teens but i typically get that odd ball to shoot 30 fps different. is it case design? do benchrest type 30 degree shoulders have a better tendency to shoot more consistant? if so why? on a side not my friends 6.5 lapua is usually single digit, go figure. i have come to the conclusion that is hit or miss.

 

[fr3db3ar]

fr3db3ar, what are your barrel lengths?

These are both AR's. 16" for the 308(DPMS Oracle) and 18" for the 223(R-15)

I'll have to check the numbers when I get home for SD.

 

[Rtheurer]

Another consideration here is that your shooting a Semi Auto rifle. Not saying that the AR type Platform cant be acccurate by any means.. But compared to even a semi Custom rifle you wil have to set your shoulder back enough to feed out of the magazine function. Compare that to a bolt gun where you can set the shoulder back .0015 ish..... can cause some variations that show up as higher ES and SD numbers.

Lots of Variables pointed out here with some great answers. Look at Dave Berg's results.... I can almost bet that is not a factory Semi Auto Gas gun?????? Nice job Dave..

I guess what Im saying is you might be hoping for alot in the platform your using.

Dang good Questions.
Russ T

 

[fr3db3ar]

Thanks to all for your input so far. I was just wondering over all how good my numbers were. From all the reading I realized neck tension would be a factor and I'm limited to length by the mag.

I'm fairly happy with 3/4 MOA, but when it comes to accuracy are we really ever totally satisfied?

I know I'm unlikley to be shooting single holes @ 300 like I've seen some of you guys doing but I can try. ;D

 

[Rtheurer]

I'm fairly happy with 3/4 MOA, but when it comes to accuracy are we really ever totally satisfied?

Indeed sir.... no we are not.
RT

 

[mikecr]

I think a 16" barrel is ridiculous for a 308, and has to be a contributor to the higher ES.
The poor design of the cartridges(223/308) is another contributor -from a precision reloading perspective.
Gas taken from the bore, by design, is another contributor.

All things can be overcome, but not assumed away.

 

[amlevin]

I'd satisfied with those numbers even though some may consider them terrible.

I don't bother too much with ES for all the stated reasons. One fast round and one slow round can give you a monster ES but what did the majority of the rounds do?

Yesterday I tested some loads that shot great at both 100 and 300 yards with .3 MOA or less accuracy.

15 rounds over the chronograph yielded an average speed of 2550.5 fps.

ONE round was slow @2514.9 and caused an extreme spread of 50.6 fps. (High was 2565.5)

However, the Mean Absolute Deviation was only 9.8 fps.

It only takes one round to disappoint you with a high ES and then one tends to loose track of the other rounds that in many cases were within only a few feet per second in speed. 7 shots were less than 5 fps in variation.

Now all I have to do is figure out what caused that one round to be slower than all the others.

BTW, these loads were all in Winchester Brass, neck turned, 3x fired, and not annealed. The bullet was a Hornady 178 gr A-Max (not match).

Next outing I will have the cases annealed and pay very close attention to neck tension.

 

[Beau]

fr3db3ar, what are your barrel lengths?

These are both AR's. 16" for the 308(DPMS Oracle) and 18" for the 223(R-15)

I'll have to check the numbers when I get home for SD.

The best ES I've ever measured out of a gasgun was 20 fps, and that was only over 5 shots. I'm sure another 5 would have widened that.

Over 10 shots, the best I've ever measured was 35fps ES.

Boltguns seem to be a different story, even with "inaccurate" cartridges like the 30/06.

By far, most loads I've measured that used dumped charges have an ES of over 50fps with many over 100fps. A large portion of the high-spread loads exhibited excessive pressure, however.

Looking back over my data, it was disturbing how many of the weighed charges were clustered around the high SD & ES end of the data!

 

[fr3db3ar]

Ok, I ran the numbers for the SD

223 = 22.7
308 = 13.4

Good ? Bad ?

Leave 3/4 MOA well enough alone? These are hunting guns that I'd like to shoot long range for practice.

 

[Rtheurer]

The 308 actually looks a whole lot better than I expected... how big was your sample? 5 rounds? I think you could tweek the 223 a little as I have got my NRA Servcie rifle in the teens pretty easy with Long single loaded ammo ( 600 yard line ammo)

Think about what your trying to accomplish.... I say I can do some real damage with a 1 MOA rifle....If it can hold 6" or less at 600 yrds thats pretty darn good and you could go forth with alot of confidence... Sure a sub1/2 MOA gun is what everyone wants but what the heck I wouldnt bet my life standing in a field with a good marksman and a 1 MOA rifle.
This is no kidding I ( actually a group of us)was talking to Maj Land.. Carlos Hathcock's C.O. while I was in Quantico in 2008... He said that Gysgt Hathcock's sniper rifle was a 1 1/2 MOA rifle..... It was real consistant but still a 1 1/2MOA rifle and ammo combo. Just sayin.

RussT