UPDATED: Head scratching day at the range

[RockyMtnUT]

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[Eric Musgrove]

A "Ladder test" is best done at 400+ yards. Even 600+ is very telling for barrel harmonics and vertical dispersion. Which is what a ladder test is for.

Find 3 or 4 in a row with very little vertical dispersion, and that is a good node. If your velocities are even 80fps, that shows how forgiving that node will be to velocity swings.

A ladder is not for best ES/SD.

Sorry I missed spoke when I said ladder test, I should have said OCW I had ladder test on my mind for another project. I only have a 300 max range so I guess I shouldn't even bother with it then for that gun.

 

[Eric Musgrove]

Once fired brass vs virgin.
The dreaded, and well known "6.5PRC chamber/die issue" where the SAAMI chamber is cut smaller than the SAMMI dies can size down to.
Carbon ring.
Environmental conditions like temperature (although unlikely with H1000).
Seating depth changes
Neck tension changes
Actual charge weight variations depending on how you are measuring them.

This next comment is not to throw any blame on the OP, but, not knowing what actual pressure signs might be there? Once you get to overpressure, speeds can do weird things.

I thought this issue was being found with harder brass such as ADG? I read on a thread here where is is not an issue with softer Hornady brass. I am able to bump the shoulder back no with no problems?

 

[Eric Musgrove]

I am not a big fan of the ladder system. For the following reasons:

1) Your data point is a single round per load. A sub 20 fps extreme spread is not bad so consider you realy don't know whether shot 1 was at the bottom of its ES and shot 2 was at the top of its ES. So what looks like 5 fps could really be 25 fps.

2) Ladder's are typically done at 200 yards, if you have a 3/4 inch rifle (not bad) and two charge weights that look like they are 1/4" apart, the respective groups could generate groups centered 1.5" apart.

3) 200 yards introduces greater shooter error than 100 yards.

Try using Optimal Charge Weight Method at 100 yards and for that size case, I would go in .6 grain incrmenets. To cover all your bases load Load 1 = 57.6, 58.2, 58.8, 59.4, Load 5 = 60.0. Shoot them in a round robin order on 5 different aiming points; i.e, Shoot Load 1 thru 5, then Load 5 thru 1, then load 1 thru 5 each on its own repsective aiming point. You should find two loads with a very similar groups size and a very similar POI relative to POA. Split the difference between those two loads. See attached sample target below. On the target below, load 7 and 8 (upper right) are the optimal loads so the final load is then 46.2. In this case I used .4 increments becuase the base load is in the 40s.

I have found this method to be much more reliable and consistent than the ladder method.

Sorry I miss spoke when I said ladder test, I had that on my mind from other current project. It was a OCW test like you mention. although it is not the same as you mention here. I was trying to use less components to find the node.

 

[Eric Musgrove]

Sort your Hornady brass, they vary in weight quite a bit.
That brass has been shot 2x's?

ok, the ones in the picture, yes that was the second firing on them

 

[lancetkenyon]

No that brass has already been processed and RTL. This is a pic of the 59.0 load, maybe some how the shoulder bump was more on the first set of brass? Less bump more pressure? It was sized on a different day but I am sure I measured them.

Ejector marks and swipes. Signs of pressure.

 

[RockyMtnUT]

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[Eric Musgrove]

Ejector marks and swipes. Signs of pressure.
View attachment 380811

yeah, that's why I stopped and went home

 

[lancetkenyon]

Lance, those are supposedly the 3 shot at 59gr that hit pressure on the last trip out? Which they did.

I'm guessing there's some consistency issues going on here.

Sizing 1x,2x etc? Not sure if shoulder bumped etc. Some are shot 1 and 2X...
Possible powder charge not exactly same when he reloaded the first time?
Barrel cleaning is its own separate issue.

If you only have Hornady brass then fine... Sort out 15 new brass by weight.
Size them as consistent as you possibly can.
Start over with charges. "I'd stay under you 59".

Write down everything on ready to fire round.

Go to range foul barrel with 10+ rounds of odd ball ammo and let cool fully down or come back another day because outside temps suck right now. Then start over with the 15.

Now, those 15 cases after being fired will be slightly different than non-fired new cases even after FL sizing. Keep them identified as such.

But they have two ejector marks. So twice fired overpressure. Not just the 59.0 load.

 

[RockyMtnUT]

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[Eric Musgrove]

Lance, those are supposedly the 3 shot at 59gr that hit pressure on the last trip out? Which they did. Even those 3 rounds are inconstant ever so slight from each other.

I'm guessing there's some consistency issues going on here.

Sizing 1x,2x etc? Not sure if shoulder bumped etc. Some are shot 1 and 2X...
Possible powder charge not exactly same when he reloaded the first time?
Barrel cleaning is its own separate issue.

If you only have Hornady brass then fine... Sort out 15 new brass by weight.
Size them as consistent as you possibly can.
Start over with charges. "I'd stay under you 59".

Write down everything on ready to fire round.

Go to range foul barrel with 10+ rounds of odd ball ammo and let cool fully down or come back another day because outside temps suck right now. Then start over with the 15.

Now, those 15 cases after being fired 1x will be slightly different than non-fired new cases even after FL sizing. Keep them identified as such.

Thanks for the ideas and places to start, I have no virgin brass. I did just sort some by weight and wow a huge difference 7 grain spread, but have enough in the middle with-in a grain of each other that is once fired I can test. Scale has never been an issue and I trickle the last .1 grain and I verify it with another digital scale.

 

[lancetkenyon]

I'm confused with the 2x. overpressure. I thought they were 1x fired and hit pressure at 59gr?
I better step out on this one, my head cannot be scratched anymore. I'm bald.

They were once fired before, then fired again for this test. Twice fired in the head stamp photos. Hence, the two ejector marks. Both times showed pressure signs.

 

[Eric Musgrove]

They were once fired before, then fired again for this test. Twice fired in the head stamp photos. Hence, the two ejector marks. Both times showed pressure signs.

Correct, that was from a previous test with 156 gr Berger.

 

[bamban]

This

Just got done helping a friend with his rifle with similar problem. Tried and tried to narrow down the causes. #1 cause was he was cleaning it too much/frequently and creating more issues than needed. Let that barrel foul up then figure out other variables if present.

That is so true about load work. At the AMU ammo shop I was talking to the shop boss how they develop their 600 yard ammo for service rifles. Typical matches the barrel would have 20, 30, or 66 rounds before the 600 yard event starts.

Their load work will have the barrel with that many rounds to make sure the system is stable fouled up.