What is the desirable ES and SD for .308?

[TQB]

Hello,

What is the desirable ES and SD for .308 Win?

The rifle that I am using is a SAKO TRG 22 with factory 1:11'' barrel.

On my most accurate loads my SD is between 6 and 13 and my ES is between 14 and 36, being the lower values with Lapua Scenar 185gn, 39 gn of Vihtavouri N140 and CCI BR-2 primers.

What should the ES and SD be to insure adequate combustion?

Thank You,
Tiago

 

[AJC]

Single digets sd on a 5 shot string is ideal but less than 20 I'm still happy.

 

[watercam]

My Palma loads using Lapua SRP, 46.5gr. Varget, most any small rifle primer it seems, Berger or Sierra 155gr. match bullet:
ES - 12-15, SD - 7 today at the range with temp. about 70º...

 

[Straightshooter1]

Given that a .308 cartridge doesn't tend to produce as low SD's or ES's as cartridges like 6mm Dasher's, 6x47 Lapua's etc, I look for single digit SD and low teen ES's. Though I feel consistent high single digit ES's are possible, I haven't been able to do that . . . yet.

 

[TQB]

I got myself a A&D FX-120i WP, which seems to be an improvement from my Lyman Gen 6.
I hope I can get the the single digit SD as low teen reliably.

Thank You,
Tiago

 

[OKBoomer]

Keep in mind that your chronograph will have some error in its readings. For example, the Caldwell chronograph states +/- .25%. So, a 2600 ft./s bullet could be +/- 6.5 FPS. They don’t state if that’s a comparison with another chronograph or within the same shooting session. I suspect it’s within the same shooting session which would cut significantly into the threshold of 20 ft./s ES.

 

[AJC]

Keep in mind that your chronograph will have some error in its readings. For example, the Caldwell chronograph states +/- .25%. So, a 2600 ft./s bullet could be +/- 6.5 FPS. They don’t state if that’s a comparison with another chronograph or within the same shooting session. I suspect it’s within the same shooting session which would cut significantly into the threshold of 20 ft./s ES.

I believe that is an accuracy statement, and I have no real idea what or if consistency is a data set that is measured or reported

 

[TQB]

My chronograph is a Caldwell...

 

[Scott Harris]

Given that a .308 cartridge doesn't tend to produce as low SD's or ES's as cartridges like 6mm Dasher's, 6x47 Lapua's etc, I look for single digit SD and low teen ES's. Though I feel consistent high single digit ES's are possible, I haven't been able to do that . . . yet.

say what??? I routinely get 3-5 SDs over 20 shot strings with a 308 WIN

 

[Oleg S]

say what??? I routinely get 3-5 SDs over 20 shot strings with a 308 WIN

I’ve learned a few tricks from Scott

 

[BDman]

Some of my most accurate loads over the years had lousy chrono numbers but, if the accuracy remained at distance, I didn't care much. I experimented by trying different powders and I could usually find one that gave both. Sometimes, just a seating depth change would improve chrono numbers - but, sometimes, negatively affect accuracy. I've also improved numbers or accuracy or both with a neck tension change. I have had this discussion many times with some very accomplished shooters and believe it has to do with a particular barrel's harmonics and the powder's pressure curve.

These days, I'm mostly concerned with ES. If I can get a consistently accurate (3/8 moa or better) load with an ES of less than 20, I'm pretty much done with load development. My "go to" powders for .308 are Varget and RL 15. One of my friends, a top notch reloader and shooter, has a rifle that gets decent (.5 moa) accuracy with Varget but the chrono numbers are atrocious - ES in the 30's to 40's. With RL 15, accuracy is as good or better and ES is in the teens. Another friend has the opposite going on with one of his rifles.

There are many rabbit holes with components and load construction to get lost in when chasing accuracy and chrono numbers. Experimentation and KISS are diametrically opposed but it's what many of us do. So, change one thing at a time and maybe try shooting over another chrono. If accuracy is what you're happy with and ES around 20 you're probably GTG. Just MHO...

 

[NC308]

I am happy with single digits on the SD and low teen to single digits on the ES. But I have a few VERY accurate loads that show as much as 40 ES. With that said. I had a load that shot almost one hole 5 shot groups at 100 yards. But fell apart at 300?? I crony it and it was 50 FPS ES! Close up targets don’t tell the whole story!

 

[TQB]

Another question.

My accurate load at 100m has 2340fps and at 300m it seems to be accurate as far as I can tell with limited testing.

What would be the desirable velocity for a 185gn .308 Win round to be accurate at 300m or even at 600m?

Thanks You,
Tiago

 

[Dicko]

308 200-20x first group after ladder test. They can produce very good results

 

[Hohn]

You can calculate this for yourself. And you should, really, because an FTR shooter at 1000y will have much more stringent requirements than someone shooting shorter range or bigger targets.

All you need to do is look at the difference in impact position due to velocity at the ranges of interest.

So let's say you're shooting 1000y and you need to keep a 200.20x Berger within the X ring. You're load is pushing it 2800-2820 fps.

At 2800, it drops 28.2 moa from 100y zero.
At 2820, it drops 27.7 moa from 100y zero.

Thus, you know that if you want to hold a 0.5 moa vertical, you need an ES no worse than 20 fps.

Or else, you will need to rely on "positive compensation" to give you a better waterline than your SD/ES would predict.


So run the numbers based on YOUR speed and YOUR need.

 

[Toejoe12]

You can calculate this for yourself. And you should, really, because an FTR shooter at 1000y will have much more stringent requirements than someone shooting shorter range or bigger targets.

All you need to do is look at the difference in impact position due to velocity at the ranges of interest.

So let's say you're shooting 1000y and you need to keep a 200.20x Berger within the X ring. You're load is pushing it 2800-2820 fps.

At 2800, it drops 28.2 moa from 100y zero.
At 2820, it drops 27.7 moa from 100y zero.

Thus, you know that if you want to hold a 0.5 moa vertical, you need an ES no worse than 20 fps.

Or else, you will need to rely on "positive compensation" to give you a better waterline than your SD/ES would predict.


So run the numbers based on YOUR speed and YOUR need.

I highly discourage anyone to run 20x bullets out of a 308 at 2800-2820 fps. I’m hoping that’s a typo on your part

 

[MikeMcCasland]

I highly discourage anyone to run 20x bullets out of a 308 at 2800-2820 fps. I’m hoping that’s a typo on your part

Heard of a guy doing it with RL17.

 

[Monte F]

I highly discourage anyone to run 20x bullets out of a 308 at 2800-2820 fps. I’m hoping that’s a typo on your part

That raised my eyebrows also!

 

[PAPA65]

Don't waste your time on those number, but go by what your load shows on the target. That is what counts

 

[XTR]

Reloading is easy if you stay off of the internet.

How far are you planning to shoot. About 90% of the answers above are for long range (past 600 yards) shooting.

If you are shooting at 600 yards with Berger 168 Hybrids at 2700 to 2750FPS, that's a 50FPS ES you only get 3.8" of vertical from velocity changes.

That Lapua 185 from 2600 to 2650FPS has a difference of 4.4" due to velocity changes.

If you are getting precision that is good enough for you with a factory rifle, and if you are not shooting long range don't get wrapped up in it and have fun. Find a load that works for what you are doing and shoot it.