Reading groups OCW - input requested

[jxb]

I'm working up one as well. Please keep us posted on progress.

 

[No i deer]

See if 33.5grs is repeatable..
I like to shoot 2 groups at each charge to see if its repeatable rather go for a screamer group.
Repeatability is the key

 

[Cfshooter]

32.7 and go to seating depth testing.

 

[Checkmate101]

I plan

The problem I have is that you didn’t take the time to de coppper the barrel and break in the throat prior to this test ?
So all you have to go on is what you see here without flags.
Hopefully your choices moving forward will repeat.
Please report back

I plan on reporting back for sure. Hoping things will improve with additional break in and testing. Do you mean just getting rounds down range and a cleaning procedure for deciphering and breaking in the throat? Forgive my ignorance, but I haven’t heard about those procedures if it is something drastically different than that.

 

[jelenko]

I'm assuming the OP is asking about Newberry's Optimum Charge Weight load development.
If so, the method is specifically NOT to choose the smallest group. It's to select the charge weight that is between two other charge weights on either side that have POI's closest.
Extract from Newberry's instructions: [My emphasis added]

14. Triangulate the groups. This means to connect all three shots in a triangular form, and determine the center of the group, and plot that point on the target. Measure this point's distance and direction from the bullseye, and record the information somewhere on the target. Do this for all of the targets. If you have a called flyer, you should discount that shot, or replace it in the group if you have an additional round loaded with that charge (and having a fourth round is always a good idea).

15. You will now look for the three groups which come the closest to hitting the same POI (point of impact) on the targets. The trend of the groups should be obvious, normally (but not always!) going from low and favoring one side, to high and favoring the other side. But along the progression, there should be a string of at least three groups that all hit the target in the same relative point.

16. After you have carefully measured group sizes and distances and directions from the bullseye, you will know which three groups come the closest to hitting the target in the same POI. You now choose the powder charge which represents the center of this string. For example, if 34.7, 35.0, and 35.3 grains all grouped about 1.5 inches high, and about 3/4 of an inch right of the bullseye, you would choose the 35.0 grain charge as your OCW (optimal charge weight). This charge will allow 34.7 and 35.3 grain charges to group right with it. This will be a very "pressure tolerant" or "resilient" load.

17. Remember, don't get "bowled over" by a tiny group which falls outside the OCW zone. You can tune any of the groups to be tiny with bullet seating depth changes. After you have determined the OCW, you may want to try seating the bullets deeper or longer in .005" or .010" increments to see where your particular rifle does its best. If you're a real stickler for accuracy, you can do another "round robin" test using varied seating depths, perhaps in .003" increments. Look for at least two seating depth stages that hit the same POI and group tight as well. This said, I have often found that OCW recipes are so reliable that seating depth alterations--especially for game hunting cartridges--often don't seem necessary.
Link to his full instructions:

http://www.ocwreloading.com/about.html

 

[Doom]

In this test 32.6 is about the center of a "node" and it appears another one may be starting at 33.5 gn which is about 3% higher which is whether the next one should be.

 

[CharlieNC]

Is it just vertical? I thought OCW was done on both vertical and horizontal. But, I am no where expert on OCW.

And, to clarify - when I do an OCW, I shoot prone with a sling - 1/2 MOA groups are just great for me.

For me the horz and vert generally do go together. But as mentioned in following posts, sometimes the wind doesn't cooperate in that regard. With a stable vert charge weight, you then have the possibility to tune horz with seating depth. I elect to test both simultaneously using a hybrid version of the Boyer matrix.

 

[Doom]

For me the horz and vert generally do go together. But as mentioned in following posts, sometimes the wind doesn't cooperate in that regard. With a stable vert charge weight, you then have the possibility to tune horz with seating depth. I elect to test both simultaneously using a hybrid version of the Boyer matrix.

Vertical is most important. My range runs N-S and the prevailing winds are in that direction so it's usually easy to test both. What you can't do is try and chase the wind. If the wind is going to be a factor then you need to keep the POA the same in all cases and try to shoot in the same or similar conditions. I this case it becomes more of three Audette ladders and should be evaluated as such.

 

[BCP1980]

I know I’m a little late to the thread, new member, I have had success at a very similar load 26” barrel 1:7 twist using Berger 109lrht, 33.8g N150 seating .015 off touch fed GMM primers current velocity avg 2960 with about 275 rounds on barrel. Tested all the way up to 34.8g where primers were starting to crater and getting ejector swipe. Planning more testing this weekend