Help me figure out what's going on. Changing ES and SD

[jager]

Just putting this out there, maybe someone has some ideas.

So I do the following when developing a rifle load.

• Prepare and prime my cases as normal, generally a week or 3 before I go to the range.
• Pre weigh 50 charges into test tubes. 10 charges per weight, so I have 5 different loads to work with.
• Load powder and seat the bullets at the range using a hand press. Just before firing. 
• Find the most promising load or 2, and fire 10 rounds of that weight.

The reason that I load at the range, is because when it's clear that certain load is way too slow or showing pressure signs I don't load any more at that charge, and I don't have to pull a lot of bullets later.

The last 3 times I did this, I got excellent SD and ES numbers (well excellent for me anyway) ES under 20, and SDs in the mid single digits for a 10 shot group.

Then I go home, load 50 or a 100 of that exact same load. And when I go to the range months or weeks later, the ES and SD has doubled or tripled.  Suddenly ES is closer to 60, and SD around 20

What's going on here? It's not a 1 off event, it has happened 3 times now.

Things I'm considering:

• Leaving the prepared cases for weeks before loading maybe allows time for some oxidation to form in the necks, and that somehow improves neck tension consistency.
• The powder left in the test tubes for a week or 2 adapts to the local humidity or something
• Maybe some low grade form of cold welding between the necks and bullet occurs, and that doesn't occur on the ones I fire within seconds of seating the bullet.

Any input or ideas welcome. 

I've now loaded a new batch using graphite dry lube between the necks and bullets to see if that will maybe help the cause.

[janfred]

What powder, bullets and brass are you using? Calibre of the rifle?

Do you leave the powder in the hopper?

How exactly do you prepare your brass? What do you use to clean them? I presume you wet tumble.

I think the graphite neck lube may be successful in sorting your problem. I suspect that your second and third  suspicions are correct.

Powder should be kept in an air tight container for as long as possible. I have seen a lot of variation with powders left in the hopper for days at a time.

Something else to try is normal dry tumbling. That way you do not remove the graphite in the neck that you paid so much to put there in the first place...

[jager]

What powder, bullets and brass are you using? Calibre of the rifle?

Do you leave the powder in the hopper?

How exactly do you prepare your brass? What do you use to clean them? I presume you wet tumble.

I think the graphite neck lube may be successful in sorting your problem. I suspect that your second and third  suspicions are correct.

Powder should be kept in an air tight container for as long as possible. I have seen a lot of variation with powders left in the hopper for days at a time.

Something else to try is normal dry tumbling. That way you do not remove the graphite in the neck that you paid so much to put there in the first place...

6.5 Creedmoor, somchem S365, Hornady ELD-x bullets, Lapua brass.

I wet tumble with stainless pins. I think that might be the crux. Probably makes the necks too clean.

I don't leave the powder in the hopper. It stays in the tin, but the pre weighed charges live in sealed test tubes for a week or 2 before the range day.

Should get a chance next weekend to go and test the lubed versions. Unfortunately my closest range is an hour and a half drive, so I struggle to get there often enough.

[janfred]

I have no idea what the difference in humidity is between your reloading room and the shooting range. What has been made clear by people more clever than me is that a standard .308 charge shows a variation of up to 2 fps per %point of relative humidity.

Juat some food for thought

[Treeman]

Are your cases all same make and same number of firings ?
Are you testing the SD over same number of shots ? Remember the bigger the test numbers the bigger the SD and likely the  ES may become. I am saying that 3 shots is 3 shots and the spread may be low, but the take same load same day and shoot 20 shots - you far more likely to be reporting what you reporting. ( Do not know if I am being clear )

I believe you are more likely to add problems by adding loading steps like graphite. Your uber clean cases should shoot like first shot cases, your dry tumbled cases are likely not to be as finicky, they "dry tumbled" have their own personality which you then keep if you do not S/S clean them. I have noticed that small caliber cases seem more prone to change in personality than say .270 Win - my 223 really gets a bit b'fkd. Till now, like now when reading your post, I have always doubted my findings or more like musings in this regard, but the more I think of it the more I believe some of my .223 reload issues are because I started S/S cleaning ....................sometimes and not all times.

[jager]

Are your cases all same make and same number of firings ?
Are you testing the SD over same number of shots ? Remember the bigger the test numbers the bigger the SD and likely the  ES may become. I am saying that 3 shots is 3 shots and the spread may be low, but the take same load same day and shoot 20 shots - you far more likely to be reporting what you reporting. ( Do not know if I am being clear )

I believe you are more likely to add problems by adding loading steps like graphite. Your uber clean cases should shoot like first shot cases, your dry tumbled cases are likely not to be as finicky, they "dry tumbled" have their own personality which you then keep if you do not S/S clean them. I have noticed that small caliber cases seem more prone to change in personality than say .270 Win - my 223 really gets a bit b'fkd. Till now, like now when reading your post, I have always doubted my findings or more like musings in this regard, but the more I think of it the more I believe some of my .223 reload issues are because I started S/S cleaning ....................sometimes and not all times.

I used 10 shot samples in all cases to get an SD and ES.  Still, it could be that I just got lucky, 10 shots isn't massively statistically significant.

Brass from same brand and batch, from the same box in fact.  There might have been a difference of 1 in the number of firings.

Anyway, hoping to get to a range at the end of the month, then I'll know if the graphite powder helped.

The other thing I'm considering is that the chronograph might not be the greatest, and different lighting conditions on different days might be playing a role. Going to try and borrow a magnetospeed.

[Treeman]

Yes, your average Chroni chrono will tell you your velocity too more than good enough for reloading -hunting, target shooting plinking and so forth, but if you shooting 600 m and so forth you going to need the real thing and they costly compared to the ol red reader.
If your chroni is closer than say about 9 ft you will never get true readings NEVER. ( likely the biggest cause of crazy readings - chroni too close and bad batteries)
If you shooting at different angles over chroni you also have numbers that jump about.
If you using cheap Chinese batteries or batteries of dubious consistency you can also experience some WTF moments.

I still believe the graphite will cause more issues than it will solve - usually crimping improves coated bullets consistency, but crimping comes with its own issues.

For now, make sure the chroni is up to task, then we can move forward. Do not use the coated bullets to test the chroni - you may just find a perfectly good chroni being held to blame for coated bullets behavior.

[223]

I think there are 4 things you should look at, but as always, don't ignore any other possibilities.

1. Clean case neck making contact with clean bullet shank.  Yes, there may be some form of reaction affecting the bullet pull force.  A slightly dirty or dry lubricated neck may help. The carbon deposit left from firing is also a lube.

2. Also consider that your case neck tension my change over time after seating.  This will depend on brass hardness and the amount of case neck expansion when seating the bullet.

3. Powder moisture content.  Variations do occur and can affect the final MV.

4. Chronograph accuracy.  Light-activated chronographs are very handy, but are affected by lighting conditions and especially angle.

[big5ifty]

Is the powder batch number the same for the low and higher ES loads ?

[jager]

Is the powder batch number the same for the low and higher ES loads ?

Yep. Same tin even.

I'm beginning to think it has a lot to do with a dodgy chrono.  Tried some new loads with graphite lube in the necks, slight improvement. But not massive.   

Anyway, the rounds are accurate enough (about 1MOA) for hunting, so will be using my current loads during this hunting season and work up some new loads in the spring.

[big5ifty]

What caliber is it, and how far is the chrony from the muzzle ?

I got what I consider to be fudged chrony readouts, usually my chrony will indicate 'dup' if a velocity repeats, but I had some shots just keep displaying the previous number, and all I can think of in my case is there was too much muzzle blast at five meters. I think I must go to 10 meters for 100+ grains of powder.

[jager]

What caliber is it, and how far is the chrony from the muzzle ?

I got what I consider to be fudged chrony readouts, usually my chrony will indicate 'dup' if a velocity repeats, but I had some shots just keep displaying the previous number, and all I can think of in my case is there was too much muzzle blast at five meters. I think I must go to 10 meters for 100+ grains of powder.

6.5 Creedmoor. About 3m from the muzzle. Definitely something to consider

[Treeman]

What caliber is it, and how far is the chrony from the muzzle ?

I got what I consider to be fudged chrony readouts, usually my chrony will indicate 'dup' if a velocity repeats, but I had some shots just keep displaying the previous number, and all I can think of in my case is there was too much muzzle blast at five meters. I think I must go to 10 meters for 100+ grains of powder.

6.5 Creedmoor. About 3m from the muzzle. Definitely something to consider

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I usually after some bad readings take 3 large strides, those stretch steps these days, closer to 5 m than 3 m likely somewhat over 4 m, that plus fresh batteries of reputable brand will be a very good start to eliminating faults outside of the rifle and load..

[223]

What caliber is it, and how far is the chrony from the muzzle ?

I got what I consider to be fudged chrony readouts, usually my chrony will indicate 'dup' if a velocity repeats, but I had some shots just keep displaying the previous number, and all I can think of in my case is there was too much muzzle blast at five meters. I think I must go to 10 meters for 100+ grains of powder.

6.5 Creedmoor. About 3m from the muzzle. Definitely something to consider

To keep my cheap Chrony out of the blast zone, I place it 3m away from the muzzle when testing handguns with fast-burning powder.
Magnum handguns with slow-burning powder and small to medium rifle loads 5m at least.
Large caliber rifle loads (375 and up) and those using slow-burning powder (7mm Rem Mag, 300, 338 LM etc) I test at 10m from the muzzle.  With a brake or suppressor 5 m should be good.

All this is to allow the bullet to pass over both sky screens before the blast wave or some un-burnt powder granules reach the first sky screen.

[Treeman]

I got what I consider to be fudged chrony readouts, usually my chrony will indicate 'dup' if a velocity repeats, but I had some shots just keep displaying the previous number, and all I can think of in my case is there was too much muzzle blast at five meters. I think I must go to 10 meters for 100+ grains of powder.
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10 m, ? lot a folk shooting revolvers will find the chroni being hit ever so often          I see some very wide results at the range with 38/357 owners, very wide and very high low.