What is a "Node"?

[CharlieNC]

I do not disagree about what you are saying regarding group statistics. But the topic of the thread is about nodes, and anyone who can shoot at least on the order of one moa has the ability to effectively shoot an efficient ladder or ocw test with very few shots, as the response from changing charge weight greatly overshadows the one moa capability. Examples demonstrating this are shown here daily. Of course one may find that the powder, bullet, etc does not provide suitable results and no amount of testing Will make it so.

 

[CharlieNC]

OP look a few threads below and you will find a structured ladder approach detailed by @dmoran including how to evaluate the results. It may be helpful for you to shoot duplicate shots and take the center of the impact as the input, since a single errant shot could cause problems otherwise. Or Google Dan Newberry OCW as another option for the same objective using a bit different protocol. Both these approaches explain proven methods which you can use as is or adapt.

 

[Bart B.]

anyone who can shoot at least on the order of one moa has the ability to effectively shoot an efficient ladder or ocw test with very few shots, as the response from changing charge weight greatly overshadows the one moa capability.

I've shot hundreds of 10-shot groups at 200 and 300 yards across a 3 grain spread in charge weights with 308 Win cases. All sub MOA. Small change in elevation zero's but each charge weight produced virtual equal accuracy less than a 10% spread.

Charge weights did not overshadow MOA capability. Why?

 

[Bart B.]

. I am frankly seeking .25 to .4 MOA loads that are acceptably fast and repeatable

Are those the largest groups you'll accept? Or the average? Those numbers are what winning benchrest stuff shoots inside of at 100 yards.

What cartridge and I'll suggest a fast way to find a good load?

 

[CharlieNC]

I've shot hundreds of 10-shot groups at 200 and 300 yards across a 3 grain spread in charge weights with 308 Win cases. All sub MOA. Small change in elevation zero's but each charge weight produced virtual equal accuracy less than a 10% spread.

Charge weights did not overshadow MOA capability. Why?

Changes in POI, POI, POI due to charge weight are clearly differentiated from the noise (group size capability). From your descriptions it does not appear that you evaluate POI minimization as a criteria to define a node.

 

[Bart B.]

From your descriptions it does not appear that you evaluate POI minimization as a criteria to define a node.

Of course not for only a few shots. There's no logic to doing that unless there's at least 20 shots in the group; 30 is better.

I've never thought the size of a single, tiny few-shot group represents what all shots for the life of the barrel will shoot into. Those tiny groups happen when all variables are close to their zero point or cancel each other out. I've no way to know which one happened. The odds are in favor of the latter.

Have you ever looked at all the 5-shot group sizes fired by the top ten competitors at 100 and 200 yards with the same rifle in a benchrest match? There's quite a spread in their sizes. The smallest one is seldom the first one shot.

 

[gunsandgunsmithing]

Here's a 1.67 MOA plot of 27 ten-shot groups shot with the same ammo lot:

View attachment 1015277

Which 10-shot group was the smallest? Largest? Are all of their centers at the same place?

What if it was ten 27-shot groups? Or five 54-shot groups? Three 90-shot groups?

Are you talking rimfire here or centerfire..you did mention the word "lot" when referring to the ammo used.

Many of the variables that are inherent to rimfire ammo are vastly reduced by handloading for a centerfire. Frankly, ammo inconsistency is a big part of why I no longer compete in rf. It's literally a crapshoot..and yes, often lots of testing is required to be statistically significant enough to determine good ammo from better ammo. Some would call it great, but I don't think there is any "great" rf ammo.

 

[CharlieNC]

Bart since you do not subscribe to the standard concepts of defining a node based on poi sensitivity minimization, I would be interested in knowing your theory and procedure.

 

[Bart B.]

Are you talking rimfire here or centerfire..you did mention the word "lot" when referring to the ammo used.

Centerfire; a National Match lot of 7.62 NATO M118 ammo tested at 600 yards.

A "lot" of ammo has the same component suite across all rounds, be it 5 or 5,000 rounds.

 

[Tiratore]

If you ever get the chance, attend the presentation that Eley put together on their testing program, which incidentally shows how misleading groups of a small number of shots can be. Quite enlightening.

Mean radius is harder to compute, but a better figure of merit than group size if the goal is high score or number of hits close to the center.

 

[CTK]

Are those the largest groups you'll accept? Or the average? Those numbers are what winning benchrest stuff shoots inside of at 100 yards.

What cartridge and I'll suggest a fast way to find a good load?

I am starting over on the 6.5x47. I would like to average under .5 MOA. I also load for the 280ai. I have pretty good loads for the 280ai. I have shot some great <.2" loads at 100y with the 6.5L but they were at lower velocity.

 

[Bart B.]

often lots of testing is required to be statistically significant enough to determine good ammo from better ammo. Some would call it great, but I don't think there is any "great" rf ammo.

Rimfire match ammo since the early '80's is not as good as that made earlier. All companies changed their primer chemistry. All the USA 100-yard records set before then still stand. Sub half MOA test groups for a box of 50 was normal. Nowadays, you throw a party if a lot shoots under 3/4th MOA.

The Russian Olimp match ammo imported in the early 1990's to the USA was sub 1/2 MOA stuff at 100. But the Russian hoodlums closed it down a few years later to make AK47 ammo to export to their naughty friends in other countries. That's the stuff the Soviet Bloc used winning gold internationally setting records doing so. Federal made some really good rimfire match ammo back then but quit when the powder company raised their price way out of sight.

Eley Tenex, RWS R50 and R100 are best today.

 

[Bart B.]

I would like to average under .5 MOA.

That equates to all groups being under about .75 MOA.

If that's at 100 yards, note the groups will open up about 1/10th MOA for each 100 yards further down range.

 

[Bart B.]

Mean radius is harder to compute, but a better figure of merit than group size if the goal is high score or number of hits close to the center

That's how USA arsenals usually asses accuracy. They wanted to know the average distance they'll miss point of aim. Their current 7.62 NATO M118 Spcl Ball spec is spec'd different:

Average horizontal std. deviation: 10.3 in @ 1000 yds
Average vertical std. deviation: 14.0 in @ 1000 yds

Average Horizontal std. Deviation: 1.3 in @ 200 yds
Average Vertical std. Deviation: 1.5 in @ 200 yds

That 270-shot test group I posted had the group center determined then each shot hole's distance from it measured. It's mean radius is 1.9" and extreme spread about 10 inches; rings are 6" and 12". Shot from a 22" heavy match barrel in an M1903 Springfield or Rem 700 receiver laying in a Mann rest's V block. Mean radius numbers are about 1/5th that of extreme spread. A few of its 3 consecutive shot groups were about an inch; 1/6th MOA at 600 yards!!!!! But they were scattered all over; not centered.

 

[Bart B.]

Bart since you do not subscribe to the standard concepts of defining a node based on poi sensitivity minimization, I would be interested in knowing your theory and procedure.

Load Development for Factory Barrels

1. Ensure rifle's ready; barrel 100% free floated clear of fore end.
2. Use bullets with diameter at least .0003" more than barrel groove diameter and weight in upper weight range for barrel twist.
3. Use new cases or full length sized fired ones whose shoulder's are set back .002" and die's neck is .002" smaller than loaded round neck diameter.
4. Use stick powder about 2/3 to 3/4 up speed range of those listed for bullet weight. Charge weights 2/10ths grain spread maximum.
5. Use primers favored by competitive shooters using the same cartridge.
6. Seat bullets so COAL is 1/16" less than magazine length or to have 1/32" jump to rifling for single round loading.
7. Load 2 rounds at starting charge weight listed, then 2 more in 1 grain increments up to maximum. Test these to find two weights safe at upper range.
8. Most folks shoot smaller groups slung up in prone with the rifle resting on bags; one under fore hand and one under stock toe. Shouldered rifles on bags atop benches are not too repeatable from shot to shot.
9. Load 20 rounds of each then test them in 20-shot groups at desired range. Measure extreme spread or calculate mean radius from group center.

If shots start walking in some direction as barrel heats up, fix the rifle or shoot at a slower rate. If you cool the barrel, the odds of the rifle shooting to same point after getting back into the exact same shooting position are slim. Us humans are not 100% repeatable going back into the same shooting position after getting out of it.

Go with most accurate load.

That is pretty much how a few of us developed a load for Sierra's new 155 grain Palma bullet for 308 Win ammo. Several thousand rounds were loaded for its first use in a match wherein everyone shot the same ammo from prone with metallic sights. It shot about 3" or so at 600 yards in a couple dozen rifles with different barrel profiles; as reported by these top ranked competitors. I got razzed a bit having shot the high aggregate score over 4 days shooting 600, 800, 900 and 1000 yards in 15 to 20 shot strings.

 

[dmoran]

Load Development for Factory Barrels

How about for a match barrel, and very best accuracy?
Donovan

 

[savagedasher]

First we need to know what kind node your talking about . Larry

 

[shoot4fun]

First we need to know what kind node your talking about . Larry

Probably not the "If'n I node y'all wuz cumin I'd a made you'ns a cake" node.

 

[Bart B.]

How about for a match barrel, and very best accuracy?

That was covered in the last paragraph in my post. Those rifles were match barrel equipped. Border, Kreiger, Obermeyer barrels, for example. Mine was a virtual SAAMI spec chambered .3070" groove, .2980" bore, 1:12.7" twist, 4-groove, 30" medium weight Obermeyer.

About 3 inches at six hundred yards is as good as it gets. As is 7 at a thousand. Once in a while, they all will put a few consecutive shots in an inch. Using metallic sights.

 

[perry42]

It's the idea that certain cartridge / bullet combinations have multiple velocities where accuracy is best and similar. Conversely, at velocities outside these nodes accuracy is degraded.

IMHO it's myth. Even if it's true, who cares? Any shooter will shoot the most accurate load at the highest velocity they can and stay in the pressure range they are willing to accept.

For BP shooters using cross sticks for silhouette and long range competition, knowing where to place the barrel in the sticks means knowing where the "0" node is.

perry42