220 Swift OCW testing. Where do i go from here??

[Ccctennis]

I have been working on OCW testing for my 220 swift. I took everyones advice from last time and went up from 3 shots per charge weight to 5 shots for initial testing.

I will add the photos of the targets and would like to get some opinions on where to go from here? Do i have 2 nodes, maybe three? Do i need to shoot 10 shots or more in a specific node?

Test Details.
Projectile was Hornady Varmint 55 grain SP
Powder was H380
Range 100 yards
Test was 5 shots in .3 increments.
Starting at 39.0-41.7 grains

testing was done over three days. the wind was mostly calm with occasional breezes head on.

 

[Ccctennis]

Here are the rest of the targets.

 

[Mike 338]

39.6 looks best to me.

Not sure what you've done up to this point but doing just an OCW test could be leaving some good accuracy on the table.

I usually start by finding a rough seating depth that I will do most of my initial development with. If I intend to use the magazine as I would in a hunting rig, I begin testing at maximum magazine length, assuming max mag length does not already jam the bullet into the rifling. If I want to and/or your magazine allows seating the bullet close to the rifling, that's where I start. Read this: VLD: Making it Shoot | Berger Bullets

Following Newberry's OCW development, you should then start by finding your maximum charge weight. I'd read his instructions (on left of page menu bar) http://www.longrangehunting.com/forums/newreply.php?do=newreply&noquote=1&p=1074604 . Finding your max charge weight might provide an OCW node at higher velocity.



On your particular test, I would have first found my max charge weight (which you may already have), spread the charge increments out by another 2or3 /10ths of a grain or 1%+ and tried a few more increments, working all the way up to slightly below maximum charge weight. Newberry uses 2% increments. Because all your test loads are so close together, there isn't a lot of separation in the triangulation of your groups to definitively provide the data to say, "these are the best". If you used three shot groups instead of 5 shot groups, and spread things out a little more, working your way up to just below max charge weight, you could have gotten all your data without using any extra shots. Basically, just follow the instructions.

Edit: I didn't see the 2nd series of targets. I still like 39.6.

 

[flashhole]

My experience has been 100 yards is not a sufficiently long enough distance to week out loads. 200 yards is minimum in my opinion.

 

[Ccctennis]

I wish I could stretch out to 200 yards but I only have 100 yards as my option.

Ultimately isn't everything exponential? If I am shooting .3 moa at a hundred wouldn't it open up to close to .3 moa at 200 yard? I know a bad group at a 100 isn't going to tighten up between 100-200 yards. Once I get out to the ranch this summer I can shoot anything between 300-1000 yards but I was hoping to only take out a good batch of tested reloads. I have to thin out the yotes this summer.

I agree with 39.6 was best 5. I had one group better if you throw out the shot I pulled.

 

[Mike 338]

Once you find your OCW, I'd test primers (5 shots). I try to have a good selection of primers on hand and I try them all. The one that's "supposed" to be awesome isn't always the case. Then fine tune seating depth assuming you've already located a rough sweet spot. Then fine tune powder charge in .1 or .2 grain increments in each direction but stay fairly close to your OCW.

To answer your question of "isn't it all exponential"... that's the theory. The idea of finding your OCW, which can also be done with a ladder test, is to build loads within a band that produces "stable" results. When a person builds loads which may not have stable characteristics, very minor variations may upset how that load performs, such as case wall thickness, lot to lot powder variations, lot to lot bullet variations, minor temp variations and so on. Bug holes one day can open up quite a bit another day with jumpy loads and adding more distance only exposes this as well as everything else that isn't quite right. I wouldn't assume 1/2 MOA @ 100 yds is 1/2 MOA @ 400 until you've confirmed it.

I think flashhole is right that accuracy testing is better done at somewhat longer distances. I like about 150 to 200 yds or a distance that wind won't play a significant role. Ladder tests, which may be the best method but requires an inherently accurate rifle and at least 300 yards or more so the OCW test is a good way develop loads on shorter ranges.