OCW input requested

[jackbrownii]

Got to the range this weekend to try 80 grain Berger varmint bullets in my Savage Benchrest in 6mmBR. I'm scratching my head a little trying to figure out OCW nodes.

I scanned the targets and ran them through OnTarget for the measurements. Then, I put the numbers in Excel and graphed it all. The powder in question is VV N135.

First is the target using CCI BR4 primers. There was one shot at 30.7 grains that was way out. I think I didn't have the rifle back in the rest properly, so I included a plot with it included and without.

The second target is with Federal 205M primers. I think it shows a node between 29.8 and 30.7 except for the 30.4 grain group that is higher than the surrounding ones. The groups were shot round robin and I don't recall anything unusual when I fired the shots for that group. Thoughts?

Thoughts and suggestions would be appreciated.

 

[nastynatesfish]

I was just going to post a question on this. I'm interested in learning more about the OCW liads testing. If your not using the called powder in a cartridge how do you start. Load development? What do you start you OAL at? I'm lookin at this for a 260 rem with 140s and a 7-08 win

 

[jsthntn247]

Your node is between 31.0 and 31.3 with the 205 primers. However, I would shoot 31.0, 31.3, and 31.5 again because 31.3 might actually be the center of the node but you just did not test high enough to see. Do that and then play with seating depth and you will have a fine shooting load.

 

[TonyR]

Your node is between 31.0 and 31.3 with the 205 primers. However, I would shoot 31.0, 31.3, and 31.5 again because 31.3 might actually be the center of the node but you just did not test high enough to see. Do that and then play with seating depth and you will have a fine shooting load.

+1 on this node; but I would recommend bracketing these charge weights and shooting 5 shot groups instead of 3 shot groups and 0.2 gr increments instead of 0.3 grain increments. That will help your see the node better with that small case. I have used 0.1 grain increments to find the limits of the node with my 7mm short mags which are much bigger than the BR case. It can also be helpful to shoot the ladder over a chronograph. I almost always see the lowest ES in a 5 shot string that doesn't always have the smallest vertical spread but is still very good. If you test at 200 yards, the ES can be as important as the 200 yard vertical when you take the load to 1000 yards.

 

[jsthntn247]

Your node is between 31.0 and 31.3 with the 205 primers. However, I would shoot 31.0, 31.3, and 31.5 again because 31.3 might actually be the center of the node but you just did not test high enough to see. Do that and then play with seating depth and you will have a fine shooting load.

+1 on this node; but I would recommend bracketing these charge weights and shooting 5 shot groups instead of 3 shot groups and 0.2 gr increments instead of 0.3 grain increments. That will help your see the node better with that small case. I have used 0.1 grain increments to find the limits of the node with my 7mm short mags which are much bigger than the BR case. It can also be helpful to shoot the ladder over a chronograph. I almost always see the lowest ES in a 5 shot string that doesn't always have the smallest vertical spread but is still very good. If you test at 200 yards, the ES can be as important as the 200 yard vertical when you take the load to 1000 yards.

You are correct, smaller increments would be better with that small of a case. I believe the OP is on track to a fine shooting load if those were fired at 200.

 

[jackbrownii]

Thank-you, gents. I hadn't thought about running higher. The top end was chosen after looking at a bunch of different sources for 80 grain bullets and N135. Notably, it is lower than what Berger has in their manual, but they were higher than the other sources.

Regarding smaller increments: That was in the plan for the next step of examining a node more closely. (Along with 5 shot groups. )Would you have done smaller increments in the first stage? It would seem to start to take a lot of shots to cover the range. Or would you have also covered a smaller charge range to start with?

I was rather happy with initial results on this at 200. It appears this rifle likes the 80 grain bullets more than the Berger 88 grain varmint bullets, though I may just need more fiddling with those. ;D

 

[jackbrownii]

I was just going to post a question on this. I'm interested in learning more about the OCW liads testing. If your not using the called powder in a cartridge how do you start. Load development? What do you start you OAL at? I'm lookin at this for a 260 rem with 140s and a 7-08 win

Powder selection: I did some reading on here about powder recommendations and looked in various loading manuals to find something that filled the case reasonably well for the bullet weight. QuickLoad software helped a bit, too. I was happy to see N135 doing well as I like the VV powders.

OAL, I went with 0.015" off the lands for this stage of development. Fine tuning the seating depth is upcoming.

This is the specific idea I was working with: http://optimalchargeweight.embarqspace.com/ocw-instructions/4529817134

 

[TonyR]

Thank-you, gents. I hadn't thought about running higher. The top end was chosen after looking at a bunch of different sources for 80 grain bullets and N135. Notably, it is lower than what Berger has in their manual, but they were higher than the other sources.

Regarding smaller increments: That was in the plan for the next step of examining a node more closely. (Along with 5 shot groups. )Would you have done smaller increments in the first stage? It would seem to start to take a lot of shots to cover the range. Or would you have also covered a smaller charge range to start with?

I was rather happy with initial results on this at 200. It appears this rifle likes the 80 grain bullets more than the Berger 88 grain varmint bullets, though I may just need more fiddling with those. ;D

I think you have it right. With something new and unfamiliar, I always start very low and shoot a long ladder that may cover several nodes as your data does. Just keep refining and narrowing things down, just as you haveplanned. How refined depends on what you plan to do with the gun and where you do load development. If you are testing off a bench and under a shed, then it really helps to know the bounds of the node if you plan to shoot out in the open either for prone matches or varmints. If so, a load that is at the bottom of the node during development may actually shoot at the top of the node out in the open. Same thing between morning and afternoon where there can be a big temperature swing. If you don't know the boundaries of the node, these and other variables can either put you out the bottom or the top depending on where you started out.