Ladders and OCW decipher

[Zero333]

This is my brothers rifle. He shot the OCW at 109 Yards and I shot the 2 ladders at 328 yards...

308 Win.
168 SMK
Varget
Win Brass
BR-2

Savage 11 Left hand action
Shilen 308w Pre-fit 26"
Boyd's laminate stock, pillar and glassed.
Didn't feel like setting up the chrono... sorry
Switching 10-15mph wind, the odd 20mph gust. No wind flags
Shot of Harris Bi-pod and rear bag.

Considering POI and vertical...
I was thinking around #3 - 43.2gr ?

 

[USMCDOC]

This is my brothers rifle. He shot the OCW at 109 Yards and I shot the 2 ladders at 328 yards...

308 Win.
168 SMK
Varget
Win Brass
BR-2

Savage 11 Left hand action
Shilen 308w Pre-fit 26"
Boyd's laminate stock, pillar and glassed.
Didn't feel like setting up the chrono... sorry
Switching 10-15mph wind, the odd 20mph gust. No wind flags
Shot of Harris Bi-pod and rear bag.

Considering POI and vertical...
I was thinking around #3 - 43.2gr ?

When i looked at the first target.. i was thinking 44.4 or 44.7, but as soon as i saw the second target.. i was drawn to the 43.5 load.

 

[adamjmac]

in my experience powder charge is about consistent velocity, and seating depth is about group shape. All I think we can say about these tests is to stay away from 45 and higher.

 

[jlow]

I don’t do ladders (let's not go there...) but just looking at your OCW, the most consistent average POI (i.e. an average POI that is not moving) is between 43.8 to 44.4 – it basically does not move between these. Assuming it was not a particularly hot or cold day that you shot these groups, I would choose a powder weight between the three which would be around 44.1 grains. Take that charge weight and do seating depth at 3 thousands interval both longer and shorter to find your best seating depth. Once you have that, come back and test powder weight at 0.1 grain interval if necessary.

 

[mikecr]

#1 Why would you shoot ladders in big wind?
#2 What was the chosen seating based on?

 

[Ned Ludd]

Solely based on the data you have shown, you probably are looking at a couple of nodes; somewhere around 43.5 gr, and somewhere around 44.7 gr. My first inclination might be that 44.7 gr is likely a hot load, but the 168 SMK is a fairly short bullet and you may have them seated long, so that may not be true. IF (and that could be a big IF) the 44.7 gr region is not overpressure, that is where I would likely end up for a number of reasons. However, if the 44.7 gr node is is too hot, the area around 43.5 gr would be worth investigating further in 0.1 gr increments, maybe you could test 43.2 to 43.8 gr again in 0.1 gr increments, using the OCW method (i.e. not a ladder). No reason to push the limits unnecessarily by going after the high node unless you are very confident it is not over MAX pressure. Velocity data for these loads would also be helpful in the decision-making process.

 

[A_Gamehog]

43.8 thru 44.1 the POI does not change, you could be .1 grain off between each load and the POI would not change.

Seating depth changes should tighten up that group. Repeatable load somewhere around 43.9-44.0

 

[Zero333]

Thank you everyone for your input.

Everyone has good points and I've given lots of though to everything.

Looking at ladder #2 (on the right), I find #5 (43.8gr), #6 (44.1gr) & #7 (44.4gr) are on the same vertical plane and right besides each other too. On the OCW, the same charge weights have the same POI but not the best vertical or groups size.

A_Gamehog says playing with seating depth should tighten the groups around 44.1gr. Therefore would the 44.1gr charge weight be worth a seating depth test ? or is there too much vertical on the OCW with 43.8 - 44.1 and 44.4gr to invest further testing in that area ?

From the beginning I thought #2 - #3 - & #4 (42.9 - 43.2 & 43.5gr) was a node and #8 (44.7) could be another ? Not much vertical in those charge weight either.

 

[jsthntn247]

Solely based on the data you have shown, you probably are looking at a couple of nodes; somewhere around 43.5 gr, and somewhere around 44.7 gr. My first inclination might be that 44.7 gr is likely a hot load, but the 168 SMK is a fairly short bullet and you may have them seated long, so that may not be true. IF (and that could be a big IF) the 44.7 gr region is not overpressure, that is where I would likely end up for a number of reasons. However, if the 44.7 gr node is is too hot, the area around 43.5 gr would be worth investigating further in 0.1 gr increments, maybe you could test 43.2 to 43.8 gr again in 0.1 gr increments, using the OCW method (i.e. not a ladder). No reason to push the limits unnecessarily by going after the high node unless you are very confident it is not over MAX pressure. Velocity data for these loads would also be helpful in the decision-making process.

I agree with this. I would do a seating depth OCW at 43.2. I would then pick the best seating depth and shoot 43.2, 43.3, 43.4, 43.5, 44.5 44.6, 44.7, 44.8 for 5 shot groups OCW style at 100 over a Chrony and go with the one that yielded lowest ES with still grouping good.

 

[jlow]

Thank you everyone for your input.

Everyone has good points and I've given lots of though to everything.

Looking at ladder #2 (on the right), I find #5 (43.8gr), #6 (44.1gr) & #7 (44.4gr) are on the same vertical plane and right besides each other too. On the OCW, the same charge weights have the same POI but not the best vertical or groups size.

A_Gamehog says playing with seating depth should tighten the groups around 44.1gr. Therefore would the 44.1gr charge weight be worth a seating depth test ? or is there too much vertical on the OCW with 43.8 - 44.1 and 44.4gr to invest further testing in that area ?

From the beginning I thought #2 - #3 - & #4 (42.9 - 43.2 & 43.5gr) was a node and #8 (44.7) could be another ? Not much vertical in those charge weight either.

It’s funny how the OP can read my post and skip to three post down that says the same thing and only quotes the later post?

 

[dmoran]

It’s funny how the OP can read my post and skip to three post down that says the same thing and only quotes the later post?

Maybe do to some of your other input:

I don’t do ladders (let's not go there...)

 

[jlow]

Maybe do to some of your other input:

Donovan, you are not still sore?

 

[dmoran]

Donovan, you are not still sore?

Never was...

 

[jlow]

Never was...

Could have fooled us....

 

[Zero333]

It’s funny how the OP can read my post and skip to three post down that says the same thing and only quotes the later post?

Sorry jlow. What can I say. My memory can be a bit too short at times

 

[Ned Ludd]

Zero333 - do you know what the velocities were for any of these charge weights?

 

[Zero333]

Zero333 - do you know what the velocities were for any of these charge weights?

Unfortunately no

Now I wish I had set up the chronograph.

I fear chrono results might influence my perception of the results the wrong way in this type of testing.

 

[jlow]

Sorry jlow. What can I say. My memory can be a bit too short at times

It's fine. I just want to point it out. If you are going to ask for help, it's best to give reasonable acknowledgment, that way you encourage people to continue to help.

 

[Zero333]

It's fine. I just want to point it out. If you are going to ask for help, it's best to give reasonable acknowledgment, that way you encourage people to continue to help.

Acknowledged

 

[RonAKA]

Didn't feel like setting up the chrono... sorry

My opinion is that you need to repeat the ladder test under better shooting shooting conditions while taking velocity readings on every single shot. It is also ok to shoot more than one shot at each load level, but still record the shot #, and velocity for each individual shot, so you have a complete set of data. Using powder weight only, makes the assumption that velocity produced will be proportional. Especially without having an optimized seating depth that is not necessarily going to be true. When you have the detailed data including the vertical POI for every single shot, and more you have the better, I highly recommend plotting it using Excel. It is really hard to interpret shots scattered all over a target. But, when you plot them on a graph it often becomes very clear. Excel has an X-Y scatter graph capability which lets you input velocity and elevation for every shot and then produces a graph. It can also draw a best fit line to make the results clearer. Here is an example, with three different bullets on one graph. They all produced quite similar results. I now target about 3420 fps for this gun in this bullet range regardless of powder used, and seating depth. My practice is to get the sweet spot velocity first, and then experiment with seating depth next. After that I change powder and primers trying to get velocity spread down. If you try to do it all at the same time, you end up with a dog's breakfast...