Reasonable ES/SD goals?

[HomeSlice]

I tried a test load in my new 308 (pretty used to 223 77 & 80's). I used:

LC94 Match unfired
Fed 210
42.0 Varget (carefully weighed, see chargemaster thread)
175 Nosler CC
2.800 tip to primer, +/- .002"
.002 neck tension

I didn't do primer pocket uniforming or plash hole deburring yet, my tools for .30 aren't here yet.

Here's what I got out of 13 shots (a few missed as the sun started to go down):

Avg: 2592
ES: 118
SD: 32

I was pretty disappointed by the last two #'s. My .223 match loads are usually about 1/2 that. Now this is a first workup, so I'm nowhere near frustrated yet, but it did get me thinking:

What's a reasonable goal for ES and SD? Or are they just indicators, not to be worried about if all else is OK?

I eventually intend to shoot F/TR with this thing, so I'm hoping to get some good consistent ammo eventually.

Thoughts?

Thanks,
-Slice

 

[9H_Cracka]

Re: Reasonable ES/SD goals?

You are low on velocity/powder, putting you at somewhere less than the optimum place on the pressure curve.

That 118 fps ES will kill you for F/TR - you'll be 8 ring to 8 ring on elevation chasing your tail with the elevation knob at 800-1k. 600 won't be too bad but you'll not hold the X ring.

More cowbell (I mean powder) young man... juice it up!

 

[jrob300]

Re: Reasonable ES/SD goals?

I've also seen ES tighten up with once fired brass. Especially this last lot of Win. brass.

But your load does look a little slow.

John

 

[BCP]

Re: Reasonable ES/SD goals?

I use 42.5 in LC brass, hand thrown and get really consistent results over the chrono. It took me 1.5 grains to get another 34 fps average, so if you're getting 50-60 faster on one or two maybe your chrono or scale is buggered?

 

[MitchAlsup]

Re: Reasonable ES/SD goals?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HomeSlice</div><div class="ubbcode-body">
Avg: 2592
ES: 118
SD: 32
<snip>
What's a reasonable goal for ES and SD? </div></div>

You should try for an SD of 12-15 for a 5-shot group.

I noted that your brass prep is anemic, and you did not state the precisiion to which charges are weighted.

Generaly, 175s like to be launched at 2600-2650 (although some push them faster) and this tends to want something in the 44.0-44.5 gr Varget range. So, make a batch with a stepsize of 0.3-0.4 and walk up into the 44.5-45.0 gr range looking for pressure. Then back down after pressure is seen, and look for the first accuracy node under pressure signs.

 

[AJ300MAG]

Re: Reasonable ES/SD goals?

Reasonable ES... 15fps or less.

Lapua Brass
Fed 210M
42.8 Varget
175gr SMK
2.800 O.A.L.
.002" Neck Tension

Out of a 30" Rock Creek (1/11.27)

 

[9H_Cracka]

Re: Reasonable ES/SD goals?

Didn't think to ask about the chrono.

Given my experience with them over the years, unless I set your rifle up over my chrono and shot it myself, I'd be suspect of that 118 fps number unless you have repeated this ES over several strings.

 

[dar1246]

Re: Reasonable ES/SD goals?

A finish load should end up below 10 on SDs and 22 ES. You might have to work a more on seating depth and powder. But the work is worth the effort.

My sons 308 he shot for the Junior National Record. His and mine end up around 6 SD and 18 ES.

 

[Graham]

Re: Reasonable ES/SD goals?

For long range loads I look for SD's in the single digits; not always possible, and not a guarantee, but desireable assuming good performance from the load at 300 and beyond.

 

[pbcaster45]

Re: Reasonable ES/SD goals?

Primers also make a difference. I used .003 neck tension on all these test loads. Rifle was a Savage 16FLHSS with a 24 inch Lothar Walther barrel(six groove, 1 in 10).

Bullet: Nosler 175 gr. HPBT
Powder: Hodgdon Varget 43.5 grs.
Primer: <span style="font-weight: bold">CCI-BR2</span>
Case: Lapua (3rd Loading)
LOAL: 2.875 (2.294 Base to Ogive with Stoney Point)
Average Velocity: 2621.32 fps
Extreme Spread: 14.73
Standard Deviation: 5.65
Comments: Jam length with Nosler 175 gr. HPBT is 2.312 (about 2.893 LOAL). Bullets seated to give 0.018 bullet jump.

Bullet: Nosler 175 gr. HPBT
Powder: Hodgdon Varget 43.5 grs.
Primer: <span style="font-weight: bold">Federal 210 Match</span>
Case: Lapua (3rd Loading)
LOAL: 2.875 (2.294 Base to Ogive with Stoney Point)
Average Velocity: 2609.04 fps
Extreme Spread: 30.39
Standard Deviation: 11.22

Bullet: Nosler 175 gr. HPBT
Powder: Hodgdon Varget 43.5 grs.
Primer: <span style="font-weight: bold">Remington 9 ½</span>
Case: Lapua (3rd Loading)
LOAL: 2.875 (2.294 Base to Ogive with Stoney Point)
Average Velocity: 2604.11 fps
Extreme Spread: 39.69
Standard Deviation: 12.80

Bullet: Nosler 175 gr. HPBT
Powder: Hodgdon Varget 43.5 grs.
Primer: <span style="font-weight: bold">Wolf Large Rifle</span>
Case: Lapua (3rd Loading)
LOAL: 2.875 (2.294 Base to Ogive with Stoney Point)
Average Velocity: 2630.21 fps
Extreme Spread: 25.19
Standard Deviation: 7.54

 

[HomeSlice]

Re: Reasonable ES/SD goals?


Thanks for all of the replies. I know it's a little slow, but it's the virgin load for this rifle and fairly new components - not used this brass before, etc. so I figured I'd better start out low and test the rifle, load, and get it on paper.

Will skipping some of the brass prep induce that kind of variability? I plan to debur the flash hole and uniform the primer pocket, but my stuff from Sinclair to do large primers isn't here yet. I forgot to mention it in the original post, but all of the brass had a starting weight of 178.x grains, so I guess 178.5 +/- .5 grains. I weighed about 50 to get this batch of 25. Is it reasonable to use these same cases again to see the impact of fire forming, or should I use some new ones next time so as not to introduce too many variables at once?

The chrono is one of the M2's w/o the infrared screen. It wasn't dark, but it was evening in the shade. Do you think this renders the results questionable?

I've also got some Fed 210M primers, so I'll try those next time out. I knew primers would make a difference, but the post above is pretty illustrative! Wow.

More work to do, but you guys have confirmed for me that 118ES ain't good.

This is out of a 26" 1:11" 3 groove new barrel, BTW. Forgot to mention that too.

Thanks for all the help guys!
-Slice

 

[Greg Langelius *]

Re: Reasonable ES/SD goals?

I know I've put this out before, and I also know lot of folks think it's a bit off the mark, but for a lot of what we do, I think maybe what the chrono has to say is unreliable at the levels where ES/SD are calculated.

I believe that aside from getting ballpark numbers to figure basic trajectories, maybe the Chrono is a tool better suited to BR shooting than anything more practiocal than BR.

Yes, ES and SD certainly do mean important things where LR trajectories are concerned, but my quibble is about whether the common chrono can give you numbers that are reliable enough upon which to base a canny decision on ES and SD.

It's all right there in black and white, in the Chronos' usage instructions.

Readings are accurate to +/- 1%.

In plain English, this translates to readings of 3000fps being actually somewhere between 2970 and 3030 fps.

From this we are attempting to glean ES/SD numbers that are themselves hoped to be less than 1% of the reported velocity.

Personally, I don't think that's possible to any reliable degree. The logic of the situation shouts otherwise.

Greg

 

[AJ300MAG]

Re: Reasonable ES/SD goals?

Greg a chrono is only part of the equasion. When you see a group at 300 yards that is a flat horizontal line (wind changes) the chrono ain't lyin. I don't know anyone who'd base their results on chrono readings alone, including BR competitors...

 

[Greg Langelius *]

Re: Reasonable ES/SD goals?

That's my point exactly.

 

[Short-bus]

Re: Reasonable ES/SD goals?

I've been counting on my chrono less and less recently. I was out 2 weeks ago, shot over the chrony the same load that I shot yesterday. Back then it was reading about 100fps faster than what it shot yesterday. The chrono wasn't in the shade, I had the screens up, but the sun was still shining on the "eyes" at an angle, and I think that skunked up the readings. Went out yesterday without the chrono, shot at 550 and 700 yards and backtracked my dope to get my velocity of 2450 (208 amax). Looking at my target seemed ok to me, I only have a 10x Leupold, and I can't honestly say I can hold accurately enough to fire perfectly at that range, but a couple shots dropped real low at 700, but that could have been me, or it could have been the load, but i'm sure it was me, it's not the first time that i've pulled a shot low. If you have the ability, on target in the real world performance is what you should look at, not simply what a chronograph tells you.

Branden

 

[Alan Griffith]

Re: Reasonable ES/SD goals?

Preferably single digit ES.

Alan