Need Help w/ OCW Results

[bill123]

I shot the following session today:

4 rounds each group
Berger 175gr OTM Tactical 2.81" OAL, Varget, Lapua brass

Clearly 43.5, 44.1 & 44.7 are the smallest groups. I could work up around them but I understood that I should work up around consistency between successive groups not just the smallest groups.

I'd appreciate any suggestions.

 

[davkrat]

I'd say right around 44.5 is where you want to be. Besides just the small size of the groups I like that their POI is centered around the same spot. The other loads seem to oscillate around the slightly right of center POI that those three loads hit.

On a side note 44.5 grains of Varget is my go to for my .308 and 150 grain ETips. The lighter solid copper ETips seem to behave similar to a cup 'n core in the 168-175 range. I would not be surprised if you are in the ballpark with that load. What's your speed? I'd guess maybe around 2700-2750?

 

[justgoto]

Clearly 43.5, 44.1 & 44.7 are the smallest groups. I could work up around them but I understood that I should work up around consistency between successive groups not just the smallest groups.

I think you're combining the Audette Ladder Test with Newberry's OCW.


OCW test example

When finished, I had three shots on each of the five targets, BUT (!)... I don't look for the tightest group of the five and call that my load.

Here's what I do instead, and I'll explain why later: I look for the three groups of the five that come the closest to hitting the target in the same position. I noted that in this case, the three groups from the middle of the string were the ones which happened to hit the same POI, (all within about a 3/4" overlay, and all at a 2 o'clock position with relation to the bull) with the 39.2 grain group hitting low and left from that common POI by an inch.

You need to look at the POI, not tight groups.

To me, it looks like the charge weight from 44.1 to 45, are centered height wise, but slightly right. I'd try 44.5 or so.

 

[bill123]

I think you're combining the Audette Ladder Test with Newberry's OCW.


OCW test example


You need to look at the POI, not tight groups.

To me, it looks like the charge weight from 44.1 to 45, are centered height wise, but slightly right. I'd try 44.5 or so.

Is it possible that there are 2 nodes in there between 44.1 and 45?

 

[bill123]

I'd say right around 44.5 is where you want to be. Besides just the small size of the groups I like that their POI is centered around the same spot. The other loads seem to oscillate around the slightly right of center POI that those three loads hit.

On a side note 44.5 grains of Varget is my go to for my .308 and 150 grain ETips. The lighter solid copper ETips seem to behave similar to a cup 'n core in the 168-175 range. I would not be surprised if you are in the ballpark with that load. What's your speed? I'd guess maybe around 2700-2750?

Thanks for the input!

 

[justgoto]

Is it possible that there are 2 nodes in there between 44.1 and 45?

There looks to be one node which would regularly produce a .5MOA group; using a charge weight that varies more than .5grs.

 

[bill123]

There looks to be one node which would regularly produce a .5MOA group; using a charge weight that varies more than .5grs.

Can you explain that? I'm not following you.

 

[crowsniper]

Looks to me like you need to back away from the target farther,the groups look very similar from low to high .

 

[bill123]

Looks to me like you need to back away from the target farther,the groups look very similar from low to high .

Unfortunately 100 yds is all I have now. I think I'll try another set from 44.1 - 44.7 in .1 grain increments.

 

[davkrat]

.1 might not matter a whole lot. The idea is to find a node where a fairly large change in powder charge still shoots to the same poi and group size. I'd try 44.5 and fiddle with OAL rather than power charge. Being on a node you could theoretically be a little sloppy with your powder charge and not see much change particularly at short ranges. Step it out and your likely to see some vertical if you aren't consistantly on powder charge.

 

[bill123]

.1 might not matter a whole lot. The idea is to find a node where a fairly large change in powder charge still shoots to the same poi and group size. I'd try 44.5 and fiddle with OAL rather than power charge. Being on a node you could theoretically be a little sloppy with your powder charge and not see much change particularly at short ranges. Step it out and your likely to see some vertical if you aren't consistantly on powder charge.

I thought that .1 would show me exactly where the node is but maybe it will be too hard to see a difference. Thanks for the advice.

 

[justgoto]

I thought that .1 would show me exactly where the node is but maybe it will be too hard to see a difference. Thanks for the advice.

I think you are confusing the use of the word "node."

node:
4
a : a point, line, or surface of a vibrating body or system that is free or relatively free from vibratory motion
b : a point at which a wave has an amplitude of zero


​

It appears the entire node is between charge weights 44.1 and 45; maybe just before 45.
With my 30-06; I usually find nodes about 1grain in size, occurring every 3grains or so.
I see Newberry's pattern within those charge weights. That entire pattern is the node; "that is free or relatively free from vibratory motion ."

I would choose the center-most point; that which is most "free from vibratory motion ."

 

[jsthntn247]

When I saw what you were loading I was just going to tell you to load 44.1 without looking at the target. After seeing the target 44.1 is definitely your best load just like it is in 95% of 308's. Any more testing besides seating depth is a waste of components.

 

[bill123]

I think you are confusing the use of the word "node."

node:
4
a : a point, line, or surface of a vibrating body or system that is free or relatively free from vibratory motion
b : a point at which a wave has an amplitude of zero


​

It appears the entire node is between charge weights 44.1 and 45; maybe just before 45.
With my 30-06; I usually find nodes about 1grain in size, occurring every 3grains or so.
I see Newberry's pattern within those charge weights. That entire pattern is the node; "that is free or relatively free from vibratory motion ."

I would choose the center-most point; that which is most "free from vibratory motion ."

I was interpreting the node as the center most point not a range. Is that incorrect? Does that mean it's not necessary to narrow it down to the .1 grain?