OCW help

DarrellA · Aug 24, 2018

I'm running through Dan Newberry's OCW drill. Following his procedure I came up with 6 different loads, the results of which are numbered 1 - 6 in the attached pic. I'm just working through this step ad will get to seating depth later.

But for now, this is what I have. And I gotta say, I'm having a difficult time decoding the results. If I follow the OCW instructions to find the 3 groups that come closest to hitting the same POI I think that would be 4-5-6. But damn, there's not a whole lot of difference. I could easily convince myself it should be 3-4-5.

Materials are: .308, Varget, 168g SMK, Norma brass.

Suggestions?

Thanks

Speed3 · Aug 24, 2018

I'd pick 3 and do the same ladder with seating depth. As long as it's not 2000fps slow

DarrellA · Aug 25, 2018

I remembered that I have the "OnTarget" app and did some analysis with that. As it turns out, the closest 3 strings to the POA is the 3-4-5 group, just a smidgen better than the 4-5-6 group.

According to the OCW instruction, the charge used in target 4 would be the one to use. It also says to not get bowled over by a tiny group -- the group at 4 is the ugliest!

I'm going to have to ponder on this some more and get my head around what's not obvious (to me).

Pinecone · Aug 25, 2018

What charge weight increments did you use?

I see MANY people using too large of increments.

DarrellA · Aug 26, 2018

The charges were:

1 - 43.0
2 - 43.4
3 - 43.8
4 - 44.3
5 - 44.7
6 - 45.2

It's the horizontal stringing in #4 that really has me scratching my head. All shots were round robin with a minimum of 3 minutes between shots. 24" SS bull barrel in a DPMS upper.

Moorvogi · Aug 26, 2018

I can see why you're having a hard time w/ this one. I'm still new to OCW also but unless i'm imagining things, the POI is walking in a circle. Could it be that you're "scatter group" is #4?? I haven't looked at load info in books but i'm curious what happens if you add another 2 targets (45.6 and 46gr). In all my other OCWs i had a spectacular group right before a scatter group. This is why the OCW made a huge diffrence for me because conditions change and BAM.. there goes your load all over the place.

Moorvogi · Aug 26, 2018

Speed3 said:
I'd pick 3 and do the same ladder with seating depth. As long as it's not 2000fps slow

Good feedback for someone wanting to do a ladder, he's doing an OCW test though.

Speed3 · Aug 26, 2018

Just giving my advice, often times seating depth and neck tension play a larger factor than charge weights. Just my $.02 and I've stayed at the holiday inn.

There are generally 2 accuracy nodes, one on the lower end and one on the higher end. His powder jumps are 1% if I remember correctly, might be worth the effort to drop them to .7%.

Pinecone · Aug 27, 2018

The OCW method is to shoot for charge weight. Then once you find the proper charge, you then play with seating depth.

When I did mine, the groups got tighter the longer the loaded round, out to the max that would fit in the magazine. But it is a factory Rem 700 barrel, so likely has a porn star throat.

Speed3 · Aug 27, 2018

Pinecone said:
The OCW method is to shoot for charge weight. Then once you find the proper charge, you then play with seating depth.

When I did mine, the groups got tighter the longer the loaded round, out to the max that would fit in the magazine. But it is a factory Rem 700 barrel, so likely has a porn star throat.

I'm well aware of OCW method and only used for charge weights. Just trying to help the OP not get too hung up on charge weight (although its where everyone has to start). Seating depth and neck tension (in that order) also play a decent role in "groupings".

Don't forget, bullet selection/profile plays a role in seating depth(typically berger likes to touch lands and sierra likes a jump) as well as the throat and how the chamber was cut (aka reamer and freebore). Seating depths need to be monitored as the throat erodes (.308 has a much longer barrel life than say a 6.5-284) so you are going to have to load them longer as the throat erodes.

When first doing load testing with OCW... keep everything consistent, bullet 2 thou off the lands, cases trimmed to 1 thou differences, same lot of powder etc. Like the OP, I will start with 1% differences and then narrow it down to the higher accuracy node and then do .7% differences if they aren't touching. All of these are shot "round robin". Example 40gr shoot one...then 40.4gr shoot and move on. Once I determine the accuracy node and if all the holes aren't touching, I will go back and do .7% variances, 40gr then 40.3gr then 40.5gr etc.

Then move on to seating depth( leaving everything else exactly the same). Start off touching the lands and back off 2/3 thou increments. If the bullets don't touch, that's not your load and move on. You can either load all of your rounds long and use a hand press to adjust while at the range for seating depths...or just load them at home.

I wont get into neck tension, lubing inside of the necks and bullets, etc. That might be a might much for what the end use of the OP.

Good luck in finding "your load", its a process for sure.

DarrellA · Sep 22, 2018

After studying the numbers for a good long while, I decided that target #2 (from the OP) was where I should concentrate. So I loaded up 3 rounds .2g above and 3 rounds .2g below the original #2 charge. This is what I got. I think I picked the right spot. The centers of these 2 groups are only 0.077"/.073 MOA different from each other in POI from POA.

I may start playing with seating depth next. But I don't know …. Group 1.a is .555 MOA, Group 2.a is .506 MOA. I don't know that I have the skill to shoot much better than that no matter what I do with seating depth.

DutchV · Sep 29, 2018

So let me see if I follow this...using the OCW method (which I just discovered, and scanned) - we are chasing a powder charge that is optimum, but mostly ignoring seating depth? That is, keeping it consistent and safe, of course, but not doing anything special about it?

I've read lots of stuff, and reloaded plenty of pistol ammo, but not much rifle. You do hear different things - some rumor, some fact - just trying to make sure I'm reading it right.

Pinecone · Oct 2, 2018

Yes, find powder charge. Then adjust seating depth.

If you look up and read Optimum Barrel time, you will see why.

A lot of people have pet ways to develop loads. OCW has been validated by a LOT of people.

Funny thing is, if you do it right, for a given set of components, you end up with the same answer.

DutchV · Oct 2, 2018

Pinecone said:
Yes, find powder charge. Then adjust seating depth.

If you look up and read Optimum Barrel time, you will see why.

A lot of people have pet ways to develop loads. OCW has been validated by a LOT of people.

Funny thing is, if you do it right, for a given set of components, you end up with the same answer.

This is very helpful, thank you.

DarrellA · Oct 3, 2018

This link will take yo to the best explanation I've found regarding seating depth, read the posts by Tripwire.

http://forum.snipershide.com/threads/trying-to-understand-seating-depth-and-accuracy.98842/

He convinced me to give it a try. So I've loaded up 5 three round sets, each .003" apart, over and under the seating depth I used in the OCW tests. As soon as I can get to the range I'll see if it makes any difference.

Speed3 · Oct 3, 2018

DarrellA said:
This link will take yo to the best explanation I've found regarding seating depth, read the posts by Tripwire.

http://forum.snipershide.com/threads/trying-to-understand-seating-depth-and-accuracy.98842/

He convinced me to give it a try. So I've loaded up 5 three round sets, each .003" apart, over and under the seating depth I used in the OCW tests. As soon as I can get to the range I'll see if it makes any difference.

LOL see post #10

You will see differences in the group sizing by changing the seating depth changes. Some bullets like to be in the lands (Bergers VLD) and some like to jump (Sierra SMKs), it really depends on the profile of the bullet.

Good luck and post your results.

Squaregrouper · Oct 3, 2018

DarrellA said:
The charges were:

1 - 43.0
2 - 43.4
3 - 43.8
4 - 44.3
5 - 44.7
6 - 45.2

It's the horizontal stringing in #4 that really has me scratching my head. All shots were round robin with a minimum of 3 minutes between shots. 24" SS bull barrel in a DPMS upper.

I know I'm late to the party. I am not an expert, but being anal with these things leads to consistency, so here goes...
Your POI on #5 looks the best and trends towards #6 vs. #4. I would load up more- tightening the charges before focusing on seating depth. At long distances, .2gr of powder will be more significant than minuscule changes in seating depth.
Try this, with 4 loads of each:
44.5
44.7 (#5)
44.9
45.1

Personally, I would shoot the charge weights above, determine the best POI and then load the winner and a group +.1gr and -.1gr before worrying about seating depth.

ETA- I was taught the charge that has the most consistent speed is preferred over the one with a slightly better POI. A 25fps spread at the muzzle is not linear and still 25fps at 1000yds. If you have a chrono, use it.

.

onedash · Oct 3, 2018

Is it with new brass? I realized pretty quick that I had much better luck with fire formed (neck sized brass) and that it (Remington 700) liked 175gr SMK's better than 168gr.

DarrellA · Oct 3, 2018

squaregrouper said:
Your POI on #5 looks the best and trends towards #6 vs. #4. I would load up more- tightening the charges before focusing on seating depth.

Are you saying that #5 looks best because the POI is closest to the POA? If so, I thought the drill was to find POIs that are most consistent to each other, not closest to the POA. Am I misunderstanding that or am I misunderstanding why you like #5?

I did tighten up the charges in the next round of tests, see Post 11. The POI of the charges in that test were very close to each other. While the groups don't look that great, (but 1/2 MOA ain't bad!) I hope the seating depth drill will tighten them up a bit.

Thanks!

DarrellA · Oct 3, 2018

onedash said:
Is it with new brass? I realized pretty quick that I had much better luck with fire formed (neck sized brass) and that it (Remington 700) liked 175gr SMK's better than 168gr.

All new. And, yeah, I've been wondering about exactly that, using once fired brass.

Thanks

OCW help

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