Need help interpreting OCW test results

[Tonmarchelli]

I decided it was time to do some serious load development so I took my rifle out today to perform an OCW test on it. It is a remington 700 sendero II with aics chassis, timney trigger, and Harris bipod. The bullet components are virgin remington brass, hornady 208 amax, h1000 powder and cci magnum primers. Shot prone from 100 yards in 95 degree heat and it was windy.

I'm not an experienced shooter by any means so I'm sure some of the outliers are fliers. Not good enough to call them yet. The picture below is the target with all the hits.

I'm no pro but it seems there is a node around 75gr. And another one around that 76.4gr

Anybody else out there who can interpret it better than me. Thanks for the help.

 

[roggom]

I'd be curious to see what 75.2 was. Remember the first part of the OCW is consistant POI, so if you draw lines between the holes the center would be your point of impact. The 74.9 -75.7 are pretty close. I would make another run at 74.9 75.2 75.5 and see what you get. The 74.9 looks great but dont let small groups sway you unless they are repeatable.

 

[bh-ltr]

Agreed that I'd like to see 75.2 because you have decent similar POI between 74.9 and 75.7. If you were able to get a decent group in that same POI location I'd take 75.2 as my load. If you believe that the wind kicked that high shot a little bit right on the 77.2 load that may also make 76.8 look fairly good. I often look for 3 decent sized groups with similar POI in a row and pick the middle to allow for that load to have the greatest pressure variance tolerance possible. Even if the group is a bit larger and I have three groups in a row with the same POI and the groups are good I usually still go there. Might be worth doing a ladder test if you have a longer distance to shoot. That way you only have to shoot one bullet per load to get started and it may help you determine your OCW favorite point.

 

[Dan Newberry]

You have a big time scatter node at 77.2 grains. You can read about the scatter node at my website (google OCW and "Dan" and you'll find it).

That means the accuracy nodes should be on either side of that node, at 1.5 percent intervals.

That takes us downward to 76.0 grains. And upward to 78.3 grains.

If you don't have any pressure signs at the 78 grains area... give 78.3 grains a try, there ought to be a node there.

Otherwise, work around the 76.0 grain charge area, and alter seating depth of the bullet in and out a couple of stages, .005" apart until you find the optimal seating depth.

Other points...

Your target squares should be simple squares, empty in the center... that way you can "lock" the crosshairs into the box. The solid black aiming point isn't going to give you the best results.

You should expect to see the scatter group somewhere during a 5 stage OCW test. It's good to find it, as it gives you direction as to where the nodes should be.

If you can get that 208 AMAX to even 2800 fps (which should be easily done), it'll drift only .6 MOA per mph of wind at 1000 yards. That's pretty impressive. You've got to drive the 6.5's like you literally stole them to get those kind of drift numbers at 1000.

Good luck.

Dan

 

[jfields]

You have a big time scatter node at 77.2 grains. You can read about the scatter node at my website (google OCW and "Dan" and you'll find it).

That means the accuracy nodes should be on either side of that node, at 1.5 percent intervals.

That takes us downward to 76.0 grains. And upward to 78.3 grains.

If you don't have any pressure signs at the 78 grains area... give 78.3 grains a try, there ought to be a node there.

Otherwise, work around the 76.0 grain charge area, and alter seating depth of the bullet in and out a couple of stages, .005" apart until you find the optimal seating depth.

Other points...

Your target squares should be simple squares, empty in the center... that way you can "lock" the crosshairs into the box. The solid black aiming point isn't going to give you the best results.

You should expect to see the scatter group somewhere during a 5 stage OCW test. It's good to find it, as it gives you direction as to where the nodes should be.

If you can get that 208 AMAX to even 2800 fps (which should be easily done), it'll drift only .6 MOA per mph of wind at 1000 yards. That's pretty impressive. You've got to drive the 6.5's like you literally stole them to get those kind of drift numbers at 1000.

Good luck.

Dan

Dan,

I'm glad to see you on the Hide! I have read your articles and been using the OCW method for the last couple of years with great results. Your method makes the most sense for load development and just plain works.

Thanks,

-J

 

[AZ.noob]

Hey Tonmarchelli... I'm out on the west side also... where do you shoot?

Windy again today, tomorrow, Friday... I'm wanting to get out to do a little load development myself, but may wait for more favorable conditions. I'd just assume eliminate any variables that I can.

 

[Tonmarchelli]

Thanks for all the help so far guys ill keep updating this thread with further tests. It's awesome to get advice from the master himself. I think based off of what I've heard I'm going to run a few other tests. One exploring that low node around 75gr so ill do 74.9,75.2,75.5. The other one will look at dans suggestion on the scatter node that Dan pointed out. It sounds perfectly logical. And falls right where I've seen people's loads. Right around 76.0. And look at the 80.3 area. But I'm hesitant to run at or near max loads on the gun.

Or is my thinking totally off?

 

[Tonmarchelli]

Hey Tonmarchelli... I'm out on the west side also... where do you shoot?

Windy again today, tomorrow, Friday... I'm wanting to get out to do a little load development myself, but may wait for more favorable conditions. I'd just assume eliminate any variables that I can.

Hey. I live in surprise. My 100-200 spot is out bell/sun valley parkway. I'm still searching for that great 600-1000 yard spot.

 

[Dan Newberry]

78.3... not 80.3...

If you can get a satisfying load under max, that's the way to go. Brass isn't getting any cheaper...

 

[Tonmarchelli]

78.3... not 80.3...

If you can get a satisfying load under max, that's the way to go. Brass isn't getting any cheaper...

Thanks! 80.3 probably wouldn't even fit in the case.

Dan does my next phase of testing sound like a good approach? I want to find a load so. Can start to stretch my distances out.

 

[SICARIO]

Here are some Targets I made up too, if you want printed targets: http://www.snipershide.com/shooting/snipers-hide-reloading-depot/187766-ocw-targets-download.html

 

[High Binder]

Here are some Targets I made up too, if you want printed targets: http://www.snipershide.com/shooting/snipers-hide-reloading-depot/187766-ocw-targets-download.html

Nice, I like these! Thanks!

 

[Dan Newberry]

Dan does my next phase of testing sound like a good approach? I want to find a load so. Can start to stretch my distances out.

Yes, I'm sure you'll find what you're looking for if you cover the bases that you mention...

Dan

 

[Tonmarchelli]

Ok guys, I went out today and explored the further loads as advised by you guys. the conditions were about the same as last time. I called a few fliers as my rear bag wasn't agreeing with me today. I did call the flier on the 75.8 group. So I think with both the tests ive done, Im going to use 75.5 as my load. then mess with seating depth and continue to work on my technique to shrink the group. but that 75.5 group is .905" edge to edge so .605" center grouping right? .6 MOA? not bad for a novice shooter. (hopefully im interpreting that right.)

Here is a pic of the target. The higher charges weren't as reliable as I'd hoped. but that's OK. I'd rather not load at or near max anyways.

What do you think?

 

[Eznutz]

Tonmarchelli,

I think that is a safe bet as long as the 75.8 was indeed an interrupted shot...aka flinch of some sort. It looks good and next move on to the seating depth.

 

[Dan Newberry]

That probably was just a flyer at 75.8, as the 76.1 group goes right back to that same point of impact.

It actually does look like something between 75 and 76 grains should work for you.

Apparently the pressures got too high for good accuracy as you went beyond 78 grains, something that is not uncommon.

76.5 would have been interesting to see.

Dan

 

[Tonmarchelli]

thanks guys, It looks like im going to load up some rounds at 75.5 and see how the gun shoots. Its starting to get a little warm here in phoenix so not sure how many more good days Im going to have.