SD and ES changing as barrel gets dirty.

[powdergun]

I finally bit the bullet and bought a chrony ( Athlon). After years of reloading and using group size and ladder tests to find " The Perfect Load" without a chrony I am finally gathering some actual data about what I am shooting. My question is about how the SD and ES show changes as more rounds go through the barrels. What I am seeing is that after 2 or three groups the numbers start improving quite a bit. Is this a common observation ?

My 223 went from an ES of 65 fps on the first group ( 5 shot) to 9 fps after two groups and stayed there for the next four groups. I also saw a similar pattern with my 6.5CM but not so much of an ES on the first group then it stayed around 26 to 29 fps

 

[gunlaker]

If you start off with a clean barrel then definitely it'll take a few shots to settle down. I imagine your first one or two shots were the fastest?

 

[powdergun]

Strangely no. First shots were the slowest but not by much. Going back out tomorrow to see what happens with a different gun. This new toy is going to make me have to increase the ammo budget lol...

 

[I Dont Care About You]

Within a range, SD is totally irrelevant unless you are shooting pretty long distances. You won't see any difference on the target inside 300-400 yds at least.

 

[Lefty Dick]

Chasing statistical numbers in place of on target accuracy is a waste of time.

If a load presents a small SD/ES but shoots like crap, why waste your time…….

Shoot groups at 300, and evaluate, then break out the chrony, and whittle down the best looking groups by analyzing the statistics.

 

[Longbow]

In my experience precision is king until a little after 1 second time of flight. After that you need both. Having said that this is also driven by target size.

 

[KodiakHntr]

What I am seeing is that after 2 or three groups the numbers start improving quite a bit. Is this a common observation ?

My 223 went from an ES of 65 fps on the first group ( 5 shot) to 9 fps after two groups and stayed there for the next four groups. I also saw a similar pattern with my 6.5CM but not so much of an ES on the first group then it stayed around 26 to 29 fps

Question, are those more of a middle of the road load versus a closer to book maximum powder charge?

 

[track]

Chasing statistical numbers in place of on target accuracy is a waste of time.

If a load presents a small SD/ES but shoots like crap, why waste your time…….

Shoot groups at 300, and evaluate, then break out the chrony, and whittle down the best looking groups by analyzing the statistics.

The last time I shot a rifle (30-06) this year was, May 18, 2026. Oh, not that dreaded turdy-aught-six. Absolutely, no SD/ES was ever viewed, waste of time, especially for only a hunting rifle!

 

[boxhitch]

My question is about how the SD and ES show changes as more rounds go through the barrels. What I am seeing is that after 2 or three groups the numbers start improving quite a bit. Is this a common observation ?

yes, to a point. A sqeaky clean barrel may require fowling shots to get in the groove so to speak, but then should stabilize and be consistent for some time, then go off again as fowling gets too deep or a carbon ring forms.
Each barrel is diff as each load is diff, so numbers of shots will be specific to yours

 

[remington jim]

Es & Sd will VARY every time you go to the range and shoot ! Same gun same load same time same temp Same everything but different day . They are important to a point but do not obsess on them
I ve shot a lot of great groups with Near terrible Es & Sd s . BUT i do try to start off with decent ES and SD #s for Sure. .
In the end it’s the group size that Counts

 

[bearhunter]

Es & Sd will VARY every time you go to the range and shoot ! Same gun same load same time same temp Same everything but different day . They are important to a point but do not obsess on them
I ve shot a lot of great groups with Near terrible Es & Sd s . BUT i do try to start off with decent ES and SD #s for Sure. .
In the end it’s the group size that Counts

RJ, I agree with what you wrote.

However, most folks on this site don't shoot rifles in the same class you do.

They're trying to get match results with off the shelf hunting rifles.

The very odd jewel will give such results, but they're almost as rare as Unicorn horns, and with continued use, depending on how much they're shot, they become extinct.

Most shooters I know have anywhere from 1-5 CF rifles.

Less than 5%, at the very most, have custom rifles or rifles that have been rebarreled.

Some of them like to shoot a lot, several thousand rounds per year. Most are lucky to shoot 100 or less.

How many here have checked ES/SD on different grades of factory ammo? Not many.

Last year, I bought a bunch of ammo from a local estate sale. The fellow was a friend of mine, but never reloaded anything, because he didn't trust other people's reloads.

He had quite a bit of ammo on his shelves, mostly run of the mill stuff, but also several different Premium types.

I sold off most of it, but partial boxes don't move well.

I decided to shoot about 20 partial boxes with anywhere from 5-15 rounds, just to check extreme spreads.

There were three chamberings to shoot, 223 REM, 308Win, and 30-06.

Manufacturers were PPU, Federal, Nosler, Remington, and Hornady. Some of them, including Federal, Nosler, and Hornady were Premium loads.

I should have kept records of the results, but because I couldn't repeat the test, there really wasn't any reason to.

Regular ammo, from all of them, showed extreme spreads from 75 to 150 fps from the same box. PPU was the worst.

The Premium loads were better, but not by much, with nothing under 50 fps, with some around 100fps.

Accuracy was better with all the Premium types than all of the regular stuff.

I suspect it had more to do with the better quality bullets than ES.

All of the ammo used in this comparison were built for hunting purposes, not match winning.

 

[powdergun]

Even though I have been rolling my own for quite a while I never had a chrony. It is only in the last few years that I have added a couple of custom precision rifles to the safe and everything up till then have been factory guns. I thought picking up the chrony would help with fine tuning those rifles. Right now I am learning quite a bit as I find it very interesting as to how the chrony numbers correlate to what happens on paper.

The focus at this time is working with a 223 ( SPS Varmint in a Magpul hunter stock) and I realize it is a run of the mill gun but considering the cost of components these days it is a lot cheaper than playing with my 300WM which is a full custom but burns a fair bit of powder and premium bullets ain't cheap.

BTW: Thanks for all the info and advice. Much appreciated.

 

[bearhunter]

PG, IMHO, just use the best bullets you can afford to get as much accuracy as you can.

Every bullet type/from any particular manufacturer will have its own particular quirks. Sometimes a few will share those quirks.

Seating depths, good primers, sometimes neck tensions, and case lengths will have a lot to do with ES and even accuracy.

I've noticed that trimming cases to equal lengths can be much more effective than turning necks for thickness, which is most often a waste of time and effort, in standard factory chambers.

From reading the threads here, I learned to seat long for weight and diameter monolithic bullets very deep, instead of as close to the leade as possible for best accuracy.

I've also learned there is a very good reason for faster and slower powders for some bullets.

But, if a bullet does not have consistent jacket thicknesses all the way around for all surfaces, it can all be a waste of time, chasing small groups, but the bullet is still accurate enough and suitable for hunting purposes at reasonable ranges.

 

[remington jim]

Remember THIS ! without a GOOD - GREAT Barrel there is NO Accuracy !

 

[bearhunter]

Remember THIS ! without a GOOD - GREAT Barrel there is NO Accuracy !

You can have a great barrel and ho-hum bullets and get mediocre accuracy at best.

You can have ho-hum barrels and get mediocre accuracy with ho-hum bullets

But sometimes, you can have a ho-hum barrel, with premium or match bullets, and get acceptable accuracy.

Good barrels do not guarantee great accuracy, but when teamed up with good bullets, the odds of great accuracy are exponentially increased.

 

[todbartell]

Recently cleaned my 6.5 PRC and fired 1 fouler shot.

Next 5 rounds had an SD of 11 fps , After 30 rounds the SD was 8.6

 

[track]

Remember THIS ! without a GOOD - GREAT Barrel there is NO Accuracy !

That's right, all of my 8 custom "hunting" rifles achieved 1/2" or smaller group accuracy. I perfer stainless steel barrels with cut rifling, they have always performed.