Question regarding OCW

[RickInFL]

From Dan Newberry's OCW instructions...

"3. Consult at least three load data sources for maximum charge weight for the powder you've selected. Powder manufacturers are the most reliable source. You must then decide on what your maximum charge will be.

4. Back away from the maximum charge by 7 to 10 percent, and load one test round with this charge. Add 2% to the charge weight, and load another cartridge with that charge. Load a third test cartridge with the next 2% graduation. You will use these three cartridges for sighters, and more importantly to determine pressure tolerance in your individual rifle.

5. Add another 2% or so to the charge level used in cartridge #3 of step 4, and load three rounds with this charge weight. Add .7% to 1% to this charge, and load three more. Add that same graduation again, and load three more. Continue adding the chosen graduation until you have moved ONE increment above your chosen maximum powder charge."

I'm loading .308 168gr HPBT and IMR4064 with Lapua brass

Based on Dan Newbery's figures I'll be starting my .308 OCW loads at 42.5 grains of powder, which is 2.0 grs above the Nosler manual which suggest a starting load of 40.5 grains and a max load of 44.5 grains. Am I calculating this correctly in that using the OCW charge weight recommendations that I'll not load the first 2 grains from Nosler's min charge weight?

Also do I need to deduct .4% from the published data for the Lapua brass?

Thanks.

 

[8andbait]

You can start anywhere you wish within the weight range. I believe Mr Newberrys criteria is primarily for hunting weapons where we typically want accuracy and speed.
You can certainly start at the bottom charge weight and load three each at .3 gr increments and work your way up. You should see 2 or 3 obvious charge weights that will work if you start at the bottom. Remember you are not looking for the smallest group rather two or three consecutive groups that have the same or very close center point to each other.

I have used his method many times and it works nicely. Good luck

 

[RickInFL]

Thanks 8andbait, after reading into it further and watching a couple of videos I realized why he was starting well above minimum start loads ... I appreciate the input.

 

[el matador]

I think you're missing step 4. He recommends starting 7 to 10 percent below the max, so the first load you fire should be 40.0 to 41.4 grains somewhere, not 42.5. Trying to decide exactly where to start can be a pain. I usually decide on how many groups I want to shoot and what range of charge weights I want to cover, then work backward from there. If you want to go from 42.5 grains up to max and shoot 6 groups you would use .5 grain increments and load as follows:

Sighters/foulers (1 shot each): 41.0, 42.0
Groups(3 shots each): 42.5, 43.0, 43.5, 44.0, 44.5, 45.0

Some people like to shoot a straight pressure test before doing any kind of load development so they know where work from. To do that you could simply load 1 of each charge weight above and go shoot them. Once you see pressure signs use the next lower increment as your max load. This can be handy if you're using an unfamiliar cartridge or powder.

 

[azsugarbear]

I start about 2-3 grains below published maximum and then load one bullet at that amount. I then increase charge o.5 grains and load another and so on. I will usually stop about 4-5 grains above maximum for final load. But just because I load them all - it does not mean that I shoot them all. I shoot the lowest charge bullet over a chrony and slowly work up. I stop when I get a slightly sticky bolt. My new max charge then becomes one full grain below the sticky bolt charge. I pull the bullets from all unfired loads and use them for foulers.

Once I have established my max in my rifle, I then load 2 or three (depending on how many targets I am shooting) and then load down in half grain increments until I have about 10-12 different loads to shoot. I will usually find a couple of nodes somewhere in there.

 

[Bbear]

I do a bit different and combine two steps.
I'll do similar to assugarbear and start in the middle of the range and using .5 gr increments load to .5 gr OVER max. I'll load 5 of each round. Then shoot the OCW checking each case for pressure signs. As SOON AS I HIT PRESSURE SIGNS I STOP THE TEST!
If/when I find the node, the other 4 rounds of the one's that made up the node will go through the magnetospeed for velocity.
Then, back to the bench for fine tuning.

 

[RickInFL]

Thanks for the input everybody, I did go back and load rounds starting at the min start charge and worked my way up to where I started initially so next step is making it the range to see what they look like.