OCW results interpritation

[Dr. Richard Gray]

Crimping also affects flyers. I wouldn't mess too much with seating depth or at least be very observant with your cartridge specs. Also, you might try letting the barrel cool down between shots. Whereas the barrel heats up will also cause some variations.

 

[Dr. Richard Gray]

In group 2 and 5 you have a 1 marked next to the flyer (so to speak). If that is your 1st round and the others are 2 and 3 respectively. It appears that barrel temperature is your factor.

 

[Monteria]

It's a mountain rifle with a pencil thin fluted barrel. It is floated, but I am very cognisant of heat and always allow cllong between every shot. They are not 1st shots. They are marked first bad shot.

 

[asd9055]

What you are doing is a combination (modified) Satterlee/Ladder Test (round robin, which is good for the ladder)
In Satterlee you look for velocity nodes. In Ladder you look for smallest vertical displacement. I have not plotted your pressures, so with Ladder Test, I would pick load #4. You can plot your pressures and see where your velocity node would be.
Before proceeding I would do bullet seating test with which ever load you pick.

QL works but has to be calibrated.
For that wide of temperature changes I would develop loads for maybe 3 temperature ranges If I were to shoot long range

 

[Monteria]

I suppose it is somewhat of a hybrid. I see no reason to shoot loads without the chrony. I would like to see small SDs, but really the point of plotting velocity is more for QL tuning. Unfortunately I dont think the chrony is very accurate. The magneto speed, which I dont use during load development, consistently returns more consistent and higher velocity readings... That, I suppose, just is what it is.

 

[asd9055]

I suppose it is somewhat of a hybrid. I see no reason to shoot loads without the chrony. I would like to see small SDs, but really the point of plotting velocity is more for QL tuning. Unfortunately I dont think the chrony is very accurate. The magneto speed, which I dont use during load development, consistently returns more consistent and higher velocity readings... That, I suppose, just is that it is.

I like to use both. I spend the last few months researching and talking to long range competition shooters about load development. My take and personal belief is, bullet seating comes first. Figure out the most "forgiving" jump. Then develop the load with which ever method works for you.

 

[Korhil78]

I would still find my max and use the lower node if you are worried about pressure in hot temps. You are using retumbo powder which is pretty temp stable so I wouldn't worry too much about it unless you are loading right up to max pressure.

 

[Monteria]

According to Quickload forecast, which I did previously tune using magnito speed numbers, the highest load in that run should be just barely over pressure at 95°. I've been pondering that since it was first mentioned this morning and, considering the time of year, I think it's time to push for pressure at today's temps and adjust down for pressure next spring when temps start to rise again. So next Saturdy I should have a new OCW test to ponder.

 

[Roninco]

Listen to the "Modern Day Sniper" podcast, episode 14 on April 1, 2020. Scott Satterlee describes load development and bullet seating tests. He advocates bullet seating test first then load development. Not the gospel but interesting information.

 

[Dr. Vette]

You're going to waste a lot of components going by 0.2.
For Weatherbys (257/7mm/300/340) I use 0.5gr as my smallest change, and it works great. There isn't enough % difference in charge to see much going by 0.2 grains at a time.

 

[asd9055]

Just one more thing ti keep in mind.
According to Berger, the 215 grn bullet in 10 twist rifle at 2915 fps is marginally stable in the cooler temperatures. Getting stable in warmer weather. Altitude will make a difference as well.

 

[corsair4360]

I spent a bit analyzing your target photos and have a question. The 84.2 grain load looks like two shots amost in one hole and another an inch away. Is that shooter error or? How about repeating that test and let us know the results. Hope that helps

 

[asd9055]

Corsair,

I think the third hole is on the data sheet. So they make a triangle with about 2+ inches on each side.

Monteria,
Any reason you like to go to the 215? If you check to see what Weatherby sells for the 300, its a range from 150-200 grns. I shoot 180 in my old 12 twist and 200 in my new 10 twist. Less than 1/2" MOA each

 

[Doom2]

Just my opinion. But here goes.

You noted you shot round robin. Since you are shooting a rather stout rifle getting set up consistently is critical and I suspect some of your spreads are associated with not getting set up consistently. Try not shooting round robin.

I would also recommend not using the chronograph when shooting 3 shot groups and concentrate only on the target. Your standard deviations are meaningless. The ES tells you something but not enough to really depend on.

I think you can try working around #4 with a seating depth test to tighten up that spread.