SDs and ES

[dar1246]

I have most of my SDs around 7.5 but you hear of loaders getting them down to like 3 to 5. How do you achieve these types of numbers? And is the work worth the effort from 7.5 to 4 in SDs?

Every load is fully done primer pockets, trimed,seat off the o-give,clean brass.

 

[Lindy]

Re: SDs and ES

This link might answer some of your questions:

http://www.shootersjournal.com./Features/Haps/EnglemanChronographStatistics.pdf

Consider also that your chronograph is probably not all that accurate anyway.

The test of a load which matters is not the chronograph statistics, but how the load shoots.

 

[dar1246]

Re: SDs and ES

Great article. Thanks

 

[kombayotch]

Re: SDs and ES

-Ensure your charge weights are uniform.
-Ensure your necks aren't hard (anneal)
-Ensure that your neck IDs are clean and smooth. A quick twist with a bronze brush with 0000 steel wool wrapped around it works well. Some will go as far as to polish the necks and even lube them.
-Ensure that you have uniform neck tension. This can be verified with gage pins.
-Try different primers to see which one performs best in your load.

 

[ChadTRG42]

Re: SDs and ES

I really think it's a little bit of luck to find a combination that will give you extremely low SD's and ES's. I've played with many different powders and calibers, and see a lot of decent ES in the 15-30 fps. I have found one load in my 260 Rem that had a 4.5 fps spread and a 1.5 fps SD on 7 rounds. It shot awesome, and that's the load I use. I've never seen anything this low and was shocked. I really think you have to pick the best powder for the given bullet weight and barrel length you are shooting to achieve the best results.

 

[dar1246]

Re: SDs and ES

I don't clean the inside of the necks out. I will try some of the steps you mention. Thanks for the help. Maybe a little luck will happen. Thanks

 

[Winchester 69]

Re: SDs and ES

Zediker:
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">A tolerable sd is 12. Anything more than that is not good; anything less than that doesn't perform any, if at all, better than a 12. However! It is at this number, so I say, where the popular tune of "...sd doesn't matter..." and its refrain of "...seen good accuracy with high sds..." starts and stops. Twelve.... Now we have an sd that "doesn't matter."</div></div>

As I read this, once you have a load that's shooting 12 or less, no further work will be beneficial to accuracy. Zediker is saying that a 4 won't shoot any better than a 7.5.

 

[GLShooter]

Re: SDs and ES

I like to get around a 10 for SD. Surprisingly an ES of 100 will often still shoot very well though I don't really on that happening every time!!

Work to get it all the same and I guarantee you it will not come out to the 1's and 2's that all the "professionals" get.

I've got a 38 PPC load that I shot one day that in 12 rounds the SD was 8.5 with an ES of 26. They all were X Ring and That's all I wanted out of it. End of test.

Greg L

 

[Lindy]

Re: SDs and ES

If you read the link I posted above, you'll find that a high ES might be used to disqualify a bad load, but it's an unreliable figure of merit for a good one.

 

[JLM]

Re: SDs and ES

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">If you read the link I posted above, you'll find that a high ES might be used to disqualify a bad load, but it's an unreliable figure of merit for a good one.
</div></div>

Actually I read that article quite awhile go Lindy and it was quite useful

Komb,

Gauge Pins? Can you elaborate?

 

[THibben]

Re: SDs and ES

Lindy,

Cheers for the article, it re-enforced my feeling and previous 'digging round' that my standard 5 shot groups are not a large enough sample for a useful SD value to be determined - and sorry I'm not about to start shooting 20 round groups. Same goes for the ES, but as you say it does allow you to throw out a 'duff' load.

Chronos now are for me an indicator of consitancy i.e. find a 'good' load that's travelling at the speed you'd hope for. Go away and load some more of this load on a couple of different nights (setting up from scratch) then try them again. If it's pretty much the same the second time out then that's good enough - trigger time's more benifit to me than <span style="font-style: italic">'picking the fly *hit out of the pepper'</span> to reduce the ES or SD by a fraction.

Stay safe

English

 

[kombayotch]

Re: SDs and ES

Gage pins: http://www.meyergage.com/products/individual_class_z_pins.htm

$2.50 each, $20 buys the 8 I use: 0.3040" to 0.3080" in 0.0005" increments. These can tell you if you have donuts, if the necks have excessive taper or if you're not getting consistent neck tension after sizing. They are just precision ground rods. You use them as go/no-go gages in a hole. Basically find the largest one that fits. Very common in machine shops.

 

[Lindy]

Re: SDs and ES

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...trigger time's more benifit to me than 'picking the fly *hit out of the pepper' to reduce the ES or SD by a fraction.</div></div>

I quite agree.

In fact, about the only thing I use a chronograph for any more is checking for variations of muzzle velocity with temperature.

 

[dar1246]

Re: SDs and ES

If the SDs have a varation like 20 and a ES of 50. Don't you think that might be a uncounted for flyer. It might take a little time to work up a load but the time is well spent. If you are shooting at a spot 24"x24" at 800 it might need to be concerned as much. If you are shooting at a spot 6"x6" wouldn't you have a little more confidence in the setup of the shot if your numbers were SD 8 and ES 30.

I know trigger time is the thing. But also is dry firing. With this be said. You can do alot of practice with dry firing. When you go to the range or where ever you feel more confident in the shots.

 

[Lindy]

Re: SDs and ES

Your true ES is likely close to 6 times the SD, and perhaps more, which one would confirm by shooting a lot of rounds over the chronograph - which, realistically, few shooters are ever going to do.

Some factors which contribute to variations in muzzle velocity will increase the velocity. Some will contribute to decreases in muzzle velocity. Once in a while, those factors will all combine in one direction, which we might call "a flyer".

It's going to happen.

It may be useful to bear in mind that about two-thirds of the velocities will be within one SD of the mean. Another 27 percent or so will be between one and two SDs, and the rest will be greater than two SDs from the mean.

If your muzzle velocity averages 2600, and the true SD is 10, that means that a big chunk of those rounds will be greater than 2610 or less than 2590, and some will be greater than 2620 or less than 2580. Some of that latter group may be substantially away from the mean velocity.

That's the nature of the beast. Variations happen.

And all of that assumes that you can trust your chronograph numbers, which is a whole other subject.

We'd like to believe we can really predict based upon what we can measure. That belief has limitations.

 

[dar1246]

Re: SDs and ES

There always will be varations. I think the chrono has a good place for load development. If the load shows signs like groups at 100 and low SDs. I would be it will shoot at longer ranges. That is depending on the cartridge.

 

[dar1246]

Re: SDs and ES

I wasn't brushing the necks out. That help. Thanks

The article was very informative. I started shooting a 20 shot group over the chrono. That is about as much as I would like. There is alot of great info there.

 

[kombayotch]

Re: SDs and ES

The neck is often where the problems lie...

 

[Carnivore]

Re: SDs and ES

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">I really think it's a little bit of luck to find a combination that will give you extremely low SD's and ES's. I've played with many different powders and calibers, and see a lot of decent ES in the 15-30 fps. I have found one load in my 260 Rem that had a 4.5 fps spread and a 1.5 fps SD on 7 rounds. It shot awesome, and that's the load I use. I've never seen anything this low and was shocked. I really think you have to pick the best powder for the given bullet weight and barrel length you are shooting to achieve the best results. </div></div>

OK Chad, since I shoot a 260 also, give up the load information! I'm looking for something better than I have now....

 

[ChadTRG42]

Re: SDs and ES

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Carnivore</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">I really think it's a little bit of luck to find a combination that will give you extremely low SD's and ES's. I've played with many different powders and calibers, and see a lot of decent ES in the 15-30 fps. I have found one load in my 260 Rem that had a 4.5 fps spread and a 1.5 fps SD on 7 rounds. It shot awesome, and that's the load I use. I've never seen anything this low and was shocked. I really think you have to pick the best powder for the given bullet weight and barrel length you are shooting to achieve the best results. </div></div>

OK Chad, since I shoot a 260 also, give up the load information! I'm looking for something better than I have now.... </div></div>

LOL! How much you willing to pay!