115gr VLD loads for .243AI?

[BlackHawk95]

Hey guys, Great site. Well hopefully My .243 AI will be ready soon, Its my first semi - custom rifle. Ive been looking at alot of data for this cartridge and found a few loads for it. I looked in the sticky post too, but didnt find what I was looking for.

The rifle is a Winchester M70 action thats been blueprinted with all the tricks. barrel is a 27" 1 in 7 twist Lilja 3 groove in a Choate stock. Im mainly wanting to shoot the 115gr Berger VLD's or the DTAC 115. Ive only found two loads for this weight. Does anyone have any suggestions?

Is it also possible to take .243Win data and add 7% to the max and use that number as a max load for the .243AI?

Thanks in advance.

 

[chino1969]

Blackhawk95,
While I don't have an answer, here's how I would find a starting point. I'm assuming the brass has already been fireformed to the Ackley chamber. Start at the max. load for the parent .243 case and go up from there in .3 grn. increments and use a chronograph. The max. or stopping point should be no more than 7% above max. load for the parent cartridge. Ideally, if you have a 200 yd. range you can begin load development and note your velocities. For each .3 grn. increment, you will see a resultant velocity increase. At some point you will see no velocity increase with an increase in powder charge; the velocity may even drop. Your target should show an upward point of impact trend, corresponding to your velocity increase. At this point you are in an 'overbore' situation where the extra powder is not giving you more velocity. Somewhere in this climb, before reaching over bore, you will notice shots grouping together; you are actually doing an abbreviated ladder test. For example, you just shot your 12 shot test beginning with 45.0 grn. of H4831. You notice that three shots are grouped close to each other at 45.6, 45.9, and 50.2 grn. Pick the 45.9 grn. charge for further experimentation. Change seating depth, etc., but that charge should be real close to what you are looking for. Dan Newberry does a very good job of explaining the ladder test with more detail.
Chino69

 

[BlackHawk95]

Chino, Thanks for the reply. Ok, I was thinking I could use the .243 win data and go up 7% from there. Right now Im going to try three different powders Retumbo, H1000 and RE-25. From what Ive read, these are slower and cooler burning powders. So it may help with barrel wear.

I was planning on fireforming the brass buring barrel break-in, so when the barrel is ready Ill have the brass to work on accuracy laods.

Thanks,
Jerid