OCW: Do you like 3, 4, or 5 shot groups?

[Bc'z]

Well if the 3rd is horizontal with the 1st 2 your at a place you need to be, providing the 1st 2 are not vertical.
Jim are you getting ready to shoot an OCW?

 

[Pawnee Bill]

I like one shot groups because the measurements look better.

Danny

Good one!!

 

[JFrank]

Well if the 3rd is horizontal with the 1st 2 your at a place you need to be, providing the 1st 2 are not vertical.
Jim are you getting ready to shoot an OCW?

Nah
I’m no good at those, I’m learning from you!

 

[rhovee]

Some May call it a 5 shot group. I call it a (3) shot group with two fliers.

 

[dcali]

More is always better. That said, groups don’t get smaller by adding more shots. A smaller number per group will get you in a rough tune quickly. But if you want to discern a good load from a great one with any confidence, you’re going to have to shoot more than a five shot group to verify. You can take advantage of the fact that groups are not truly independent to help guide you and reduce round count. If you’ve got a huge group right next to a small one, there’s a good chance one of them is lying to you, for example.

 

[Ned Ludd]

More is always better. That said, groups don’t get smaller by adding more shots. A smaller number per group will get you in a rough tune quickly. But if you want to discern a good load from a great one with any confidence, you’re going to have to shoot more than a five shot group to verify. You can take advantage of the fact that groups are not truly independent to help guide you and reduce round count. If you’ve got a huge group right next to a small one, there’s a good chance one of them is lying to you, for example.

Those lying little holes in the paper!!! LOL. The question is which one is lying? I believe it is rare, or even nonexistent to have a group shrink up tight to one ragged hole by the influence of outside random factors (i.e. wind, shooter error, etc.). So I generally would believe the huge group right next to the small one would be the liar. Nonetheless, that's where a 5-shot group can sometimes help with your confidence level. If you put 4 into one ragged hole, but slightly jerked one shot, or maybe you saw your wind flag jump out right as you let one shot go, that's usually a good sign the load has promise, even though the group spread might be wrecked with that one hole that is out.

For the OP - the whole point of the OCW test approach is to find two (or more) successive charge weights where the center points of each group impact the exact same relative spot on the target (i.e. not moving around relative to point of aim). It is not about the smallest group. The idea is that you will have then found a charge weight "window" across which velocity/barrel harmonics tends to put bullets into the same point of impact. These OCW windows are analogous to having several successive increasing charge weights print holes at the same vertical point in a ladder test. Again, you're looking for a charge weight region where barrel harmonics produce the same vertical POI. The important point with the OCW test is that three shots is sufficient to locate the center point of a group. Chances are that adding two more shots to each group won't change the center point of each group by very much.

 

[Doom]

Ned has described Newberry’s OCW approach extremely well. I will add that part of the concept is to find a charge weight that is tolerant of lot variations in powder, primer, bullet and brass. The goal is reproducible, tolerant ammunition suitable for practical long range shooting, in both commercial and custom rifles.

In reviewing many 223 and 308 loads developed by numerous methods and posted they typically fall in the OCW ranges.

Typically the loads found by this method are portable, meaning they shoot well in most rifles.

Bottom line is it works.

 

[M14AMU]

https://flic.kr/p/2iXxcTZ

I load what I think is right and if it’ll do the above from 1000 yards....it’s good enough!

 

[INTJ]

Once I have narrowed in on the potential charge weight regions/nodes as you have, I typically use 0.1 gr increments to cover each window and 5-shot groups. 5-shot groups may be a little more informative statistically, even though 3-shot groups will usually tell you what you need to know. Where 5-shot groups really offer something more than 3-shot groups is in terms of the velocity data/statistics. Once you have identified the final load(s) you want to use, go back and "validate" them by shooting 3 to 5 5-shot groups to confirm that both precision and velocity remain consistent.

This ^^^^

 

[bsekf]

Group will never get smaller after the 2nd shot! All of my rifles and loads shoot 1 shot groups beautifully!

I keep hearing that horizontal is good and vertical is bad. I presume that reasoning is taking wind into account? Misread the wind and get more horizontal?

However if you have a head or following wind, won't that cause vertical?

I do 3 shots until I get something good, then I do 5 or more. Sometimes my 5 shot groups turn to patterns and I blame my technique or my inability to read the flags or my original load wasn't really that good. Does that happen to everybody.... or just me?

Bill

 

[Zero333]

Am I the only one who does 4-shot groups during initial OCW testing ???

 

[rardoin]

Am I the only one who does 4-shot groups during initial OCW testing ???

No, you are not.

 

[hambone1971]

Am I the only one who does 4-shot groups during initial OCW testing ???

I always do 4 shot OCW testing these loads fit my 20 round plastic boxes better for labeling.
5 loads of 4 rounds each of powder to test.
If 6.5 CM I'm testing at .2 g to find the node, if 338 Lapua it will be .3 g to find the node.
You can miss a node if you use to big a .grain jump each test load.
My nodes seem to be 2.7% apart give or take.
Someone mentioned chasing the node with use.
I have a 6.5 CM now with 5000 rounds that still prefers almost the original load when new.
Its's 41.8 RL16 now 41,9 when new, still a 1/2 MOA gun.
Works for me... HB

 

[xswanted]

I usually run with 3 shot groups to test loads on a new barrel.

Once I find 2 promising loads I will shoot 3-5 5 shot groups to see if they are consistent.

Then load up to 50 and try at varying yardages to see what they'll do.

The only time I don't use this method is if the rifle in question is a bit of a barrel burner, such as a coyote calling rifle. Then I stick with 3 shot groups and strings of fire.

 

[INTJ]

Group will never get smaller after the 2nd shot! All of my rifles and loads shoot 1 shot groups beautifully!

I keep hearing that horizontal is good and vertical is bad. I presume that reasoning is taking wind into account? Misread the wind and get more horizontal?

However if you have a head or following wind, won't that cause vertical?

I do 3 shots until I get something good, then I do 5 or more. Sometimes my 5 shot groups turn to patterns and I blame my technique or my inability to read the flags or my original load wasn't really that good. Does that happen to everybody.... or just me?

Bill

Yes, the assumption is that wind causes horizontal spread. That doesn't make sense to me either as I see as many headwinds and tailwinds as crosswinds. Not to mention those times where the wind flags are pointing at each other.

 

[tomswede]

Yes, the assumption is that wind causes horizontal spread. That doesn't make sense to me either as I see as many headwinds and tailwinds as crosswinds. Not to mention those times where the wind flags are pointing at each other.

Not sure what is being said here. Head and tail winds have minimal impact ( as long as they don’t have vertical components).

 

[bsekf]

Thanks INTJ! How about a right hand twist climbs up and right and a left hand twist climbs up and left..... or the other way around..., as you increase powder!

How much vertical can you blame on cross wind?

If you shoot straight up or straight down there is is no horizontal (drop), if you shoot perfectly level, you get the most horizontal (drop). So if you are shooting on a range that is 10 degrees up or down, how much less horizontal (drop) do you get? And would it be the same up as down? If you are shooting on a 45 degree range, does the horizontal or amount of drop (trajectory) reduce by half? This has not been my experience. Shouldn't physics and gravity enter into trajectory calculations?

I've been locked in the house too long!!!!

Bill

 

[INTJ]

Not sure what is being said here. Head and tail winds have minimal impact ( as long as they don’t have vertical components).

If the terrain was perfectly flat then there would be a minimal impact. If there is a berm or other elevation change there is vertical.

Further, if you have a headwind or tailwind and you pick minimum vertical over minimum horizontal, you are not likely picking the best group.

So when I have to pick a load for competition, I pick the group shape based on the current wind conditions. That doesn't always mean the least vertical wins.....

 

[Straightshooter1]

I keep hearing that horizontal is good and vertical is bad. I presume that reasoning is taking wind into account? Misread the wind and get more horizontal?

However if you have a head or following wind, won't that cause vertical?

I've found that a chart like this is helpful with regards to this.

 

[David Milisock]

I have 2 potential nodes im fleshing out. One range is somewhere in 41.3 - 41.9 and another in the 43.3-43.9 range. To really zero in, which option would you recommend?

.2 increments (4 groups of 3 shots = 24 total shots)
.2 increments (4 groups of 4 shots = 32 total shots)
41.3 | 41.5 | 41.7 | 41.9
43.3 | 43.5 | 43.7 | 43.9

.3 increments (3 groups of 5 shots = 30 total shots)
.3 increments (3 groups of 4 shots = 24 total shots)
.3 increments (3 groups of 3 shots = 18 total shots)
41.3 | 41.6 | 41.9
43.3 | 43.6 | 43.9

I'm talking varmints, 300 yard, 5 shot groups, I tend to go for the best group in the highest velocity range. If my 6mm or 223, groups best at 3200 FPS, say 1" but groups 1 1/8" at 3,900 FPS I go for the higher velocity.

Then I go to the range with the rifle and other firearms, shooting the rifle 1 time and after 30 minutes again to get fouled cold bore zero.