Low ES and SD data

[finnaddict]

Is it possible to have low ES (20) and SD (9.2) and have POI print like a scatter gun?

 

[ShootDots]

Yes it can.. Also I don't think that 20ft e.s.'s and almost 10s.d.'s are "low"... I consider e.s.'s inside 10f.p.s. to be low. A good 1000 yard e.s. is 12 - 15>>> what you should strive for is 12 or less! I have had single digit e.s. not shoot all that good and relatively high e.s.'s shoot decent. When you have good e.s.'s and not so good of groups, try modifying the charge either up or down depending on where you are in pressure. Then work with various seating depths and finally primers selection.. You will, or I better say, SHOULD get your accuracy to where you want and keep your e.s.'s UNDER 15 and under 12 would be better..

 

[finnaddict]

Understood. I say low because that is the lowest I have managed so far with this load. It is a .308, IMR 4064, D46-170gr. This seems to be the case. High ES with decent groups. I have already been working on changing the charges some.

 

[ShootDots]

I understand... If you have some H4895 / RL-15 or Varget, you might want to try any one of those too..

 

[dkhunt14]

I agree with ShootDots. I have seen real low E.S. shoot bad at 1000 yards and seen 20 feet or so E.S. shoot good. I prefer to get the ES as low as I can get it as long as it still shoots. Matt

 

[finnaddict]

I have H4895 but only 3 rounds worth of it.

 

[Grimstod]

Yes it can.. Also I don't think that 20ft e.s.'s and almost 10s.d.'s are "low"... I consider e.s.'s inside 10f.p.s. to be low. A good 1000 yard e.s. is 12 - 15>>> what you should strive for is 12 or less! I have had single digit e.s. not shoot all that good and relatively high e.s.'s shoot decent. When you have good e.s.'s and not so good of groups, try modifying the charge either up or down depending on where you are in pressure. Then work with various seating depths and finally primers selection.. You will, or I better say, SHOULD get your accuracy to where you want and keep your e.s.'s UNDER 15 and under 12 would be better..

I second that. I tried a very low powder charge in a case once to see what it would do. Fps variance was 1fps but grouping wasn't that great. About 1.5moa plus velocities were only 1760fps. I little slow for a 174gr bullet out of a 22in barrel.

 

[amlevin]

I recently saw a huge drop in ES on my loads. I had increased neck tension. I have to "jump" my bullets as rounds that put the bullet in the lands can't be magazine fed. Spoke with a very successful BR shooter and he advocated more neck tension unless you are able to start the bullet in the lands. His feeling is that a jammed bullet provides the same dynamics as extra neck tension.

Just an observation.

 

[jsthntn247]

I recently saw a huge drop in ES on my loads. I had increased neck tension. I have to "jump" my bullets as rounds that put the bullet in the lands can't be magazine fed. Spoke with a very successful BR shooter and he advocated more neck tension unless you are able to start the bullet in the lands. His feeling is that a jammed bullet provides the same dynamics as extra neck tension.

Just an observation.

That's why factory ammo is crimped, all of it is loaded for a jump.

 

[Grimstod]

That's interesting. I imagine that getting the bullet closer to the lands would be more ideal though, right?
Are there any articles or write ups in books out there about this?

 

[Erik Cortina]

20 ES is not bad. Adjust seating depth to bring the groups in.

Most of my best shooting guns have had ES around 20, and when tuned properly, they hammer.

Do a proper seating depth test to see where the node is and see if the groups you get are satisfactory.

 

[amlevin]

That's interesting. I imagine that getting the bullet closer to the lands would be more ideal though, right?
Are there any articles or write ups in books out there about this?

That's pretty much the consensus among those that can do this. With some rifles, and shooter's preferences, that's not always possible. Own a Remington factory chambered rifle? Good luck on reaching the lands with much bullet left in the case neck. Want to shoot your rifle as a "repeater", having rounds fed from the internal magazine box? Good luck with most rounds where the bullet is "seated out into the lands".

No neck tension makes for a real mess unless you're hand chambering each round.

Different needs, different approaches.

 

[normmatzen]

Classic example of how important tuning is at long range!
If it were practical to calculate the difference in impact point at 1000 yd with a 15fps E.S. it would surprise you. But with the correct tune, either careful determination of powder charge and set back or with a mechanical tuner, the deviation in POI can be tuned out.

 

[dkhunt14]

Classic example of how important tuning is at long range!
If it were practical to calculate the difference in impact point at 1000 yd with a 15fps E.S. it would surprise you. But with the correct tune, either careful determination of powder charge and set back or with a mechanical tuner, the deviation in POI can be tuned out.

I agree mostly with this. I believe it has to do with the vibrations in the barrel and also the bullet going to sleep. Matt