Knowing a bad node..?

[timelinex]

So I worked up a load of 44.8gr varget in winchester brass and 175smk's. I seat it .005 into the lands.

I'm having a slight issue with it though. It seems like sometimes it will shoot just about the best damn group I've ever shot and other times it throws one. So for example, I shot 5 groups today at 100 yards. 2 groups were UNDER .25 moa. 2 groups were around .75moa, both with two of the shots almost in the same hole and the third in 'outer space'. The last group was slightly above 1 MOA. When I chrono'd this load, 5 rounds had an extreme spread of FOUR!

I don't have this problem with factory SW ammo, so I'm assuming its not me. I always grouped 95% of my groups in the .6 to .7 range, but never above .8 and almost never below .5

I remember reading before that if a node frequently gives you 2 rounds in the same whole and one out of it, then its actually a bad node.

So could this be a bad node, even with such badass ES??

 

[Tripwire]

Re: Knowing a bad node..?

If you know it's not you, then believe the bullet.....

 

[rideHPD]

Re: Knowing a bad node..?

Does any other combo close to it work? I haven't begun reloading yet, but from what I know about harmonic oscillators you may just be on the edge of the resonance band, and the slightest variance can through it outside the band. This could be variances in the ammunition, to very slight changes in the rifle (very very minor movement of the action, changing local forces where it contacts the stock). Unlikely, but possible.

 

[callen3615]

Re: Knowing a bad node..?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: timelinex</div><div class="ubbcode-body">



I remember reading before that if a node frequently gives you 2 rounds in the same whole and one out of it, then its actually a bad node.
</div></div>

Very interesting. Id like to get my groups tighter than they are. I seem to get the groups where 2-3 shots go in the same hole and I get one flyer that blows it out to .5-8 moa. If it wasnt for those id have a 1/4 moa gun! hard to believe.

 

[Tripwire]

Re: Knowing a bad node..?

Let's look at a few things here......

ES is a measurement of speed, round vs. round, in a series of shots; and as it's applied to load developement is a measurement of efficiency, round to round to round. The lower the ES the more efficient your system of barrel/propellant/primer/bullet/case capacity is working together, making the bullet reach a fixed point nearly at the same exact time.

Good node vs. bad node as we see it on paper, is a measurement of WHEN the bullet exits the barrel in relation to barrel harmonics and the occilation of the muzzle due to those harmonics.

It is perfectly reasonable then to achieve the perfect badass low ES, shot to shot to shot, and have the timing, or bullet exit, on a bad node in the barrel harmonics...or when the muzzle is moving the most.

Within the principles I develope a load, as many others do, with OCW, the very essance of the method is to achieve a load that will obtain a high degree of "accuracy" across a broad range of consecutive powder weights, sometimes across a whole grain or more of powder weight. This by default, during testing, generates a fairly high ES situation from your low charge weight to your high charge weight within what you deem as a good node....yet we get what we are looking for...."accuracy".

So what the OCW method of load developement proves is that ES is not the ONLY factor in developing a good load, you need to understand barrel harmonics and achieve a perfect timing of the bullet exit to get true "accuracy". If I can get the same point of impact across a whole grain or more of powder weight, which means the bullet speed increases corrosponding to the powder weight increase, then ES is basically meaningless to the equation. Of course the most prudent of us will find the middle of that good node and with all the anal retention we can muster, load forever more that exact powder weight for some degree of "consistancy"....but our own testing proves that's not absolutely necessary.

The Holy Grail of course would be a perfect ES within a perfect node, but with the barrel harmonics addressed and a good node found, it's not worth it to me to chase my tail to ensure my bullets are all flying the exact same speed within just a couple or three feet per second.

Believe what the bullet does........

 

[timelinex]

Re: Knowing a bad node..?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tripwire</div><div class="ubbcode-body">Let's look at a few things here......

ES is a measurement of speed, round vs. round, in a series of shots; and as it's applied to load developement is a measurement of efficiency, round to round to round. The lower the ES the more efficient your system of barrel/propellant/primer/bullet/case capacity is working together, making the bullet reach a fixed point nearly at the same exact time.

Good node vs. bad node as we see it on paper, is a measurement of WHEN the bullet exits the barrel in relation to barrel harmonics and the occilation of the muzzle due to those harmonics.

It is perfectly reasonable then to achieve the perfect badass low ES, shot to shot to shot, and have the timing, or bullet exit, on a bad node in the barrel harmonics...or when the muzzle is moving the most.

Within the principles I develope a load, as many others do, with OCW, the very essance of the method is to achieve a load that will obtain a high degree of "accuracy" across a broad range of consecutive powder weights, sometimes across a whole grain or more of powder weight. This by default, during testing, generates a fairly high ES situation from your low charge weight to your high charge weight within what you deem as a good node....yet we get what we are looking for...."accuracy".

So what the OCW method of load developement proves is that ES is not the ONLY factor in developing a good load, you need to understand barrel harmonics and achieve a perfect timing of the bullet exit to get true "accuracy". If I can get the same point of impact across a whole grain or more of powder weight, which means the bullet speed increases corrosponding to the powder weight increase, then ES is basically meaningless to the equation. Of course the most prudent of us will find the middle of that good node and with all the anal retention we can muster, load forever more that exact powder weight for some degree of "consistancy"....but our own testing proves that's not absolutely necessary.

The Holy Grail of course would be a perfect ES within a perfect node, but with the barrel harmonics addressed and a good node found, it's not worth it to me to chase my tail to ensure my bullets are all flying the exact same speed within just a couple or three feet per second.

Believe what the bullet does........ </div></div>

Thanks for your great explanation. I'm gonna try finding a led sled to use, to take myself out of the equation. I will do a final test to see if its me or the combo.

I did an OCW test, BUT to be honest I didn't really see results like in the examples by Newberry. His results showed OBVIOUS nodes. I saw nodes in group tightening, but I don't think I really saw POI nodes. They all floated in the same exact general region. There was no pattern of any sorts. Here was a copy of of the POI layout I made:

10,11,12 seem all fairly close, but #12 was 46.9gr of varget and the last round of it was actually overpressure and froze my bolt. Also, the groups produced were around 1.25 MOA instead of the <.5moa the other 'nodes' made.

These tests were done with my bullet .01" jammed into the lands. Would you recommend I try to take advantage of what looks like a node in the high pressure region, and test different jumps on the bullet. Since I won't be jamming the bullet into the lands, that should relieve the pressure.

 

[Tripwire]

Re: Knowing a bad node..?

The last phase of OCW is bullet seating depth adjustment.....

What that does is provide a simple effective fine tune adjustment to bullet exit timing by making the distance the bullet travels a tad shorter or a tad longer, depending on which direction you see it needs to go; which puts more physical distance between the shockwave and the bullet's exit, allowing the bullet to exit when the muzzle is more at rest. This is a finer adjustment than you can make with bullet speed and incremental changes in powder weight, which is obvious since we can see repeatable "accuracy" across a broad range of consecutive powder weights and bullet speeds within a good node. In my experience it only takes a plus/minus of no more than .005" seating depth adjustment either way to see a positive difference. One rare instance I had to go something like 8 or 9 thou longer to get it dialed in.

I know, it sounds like a bunch of mystical voodoo until you take the whole thing, which happens faster than we can imagine, and break it down by it's components, and look at it with the applicable laws of physics.

Bullet seating depth adjustment, as it's applied to OCW, is not a substitute for searching out a node. A large change in seating depth can, and often will, move you completely out of a node, which will only serve to confuse things. It comes after the node is found, and the node is proven, and it's sole purpose is to shrink group sizes with the node's middle charge weight, if that's needed at all.

If you are jammed into the lands, in even the slightest fashion, then there is only one direction you can go with respect to the principles of OCW, and that may be the wrong way, and take you out of the node.

Of course you can jam further into the lands to shorten the bullet's barrel time, but that also changes the dynamics of whats going on with the internal ballistics by raising the pressure of the load to some degree...which ultimately changes the "explosion" (technically the extremely rapid combustion of propellant in a confined space), which produces the shock wave, which produces the barrel harmonics, which you are trying to tune the load to in the first place.

Counter productive in my opinion......

Jamming in my opinion is the lazy man's way, and the uninformed man's way, to attempt making up for poor chambers, poor load practices, horrid runout, etc. Sure, some will call BS on that opinion but there's an exception to every rule anyway, somewhere, if you dig deep enough. Most people think jamming is the only way to go because they read it on the 'net.

If you have a good chamber, a trued action, and good load practices, that produce ammo with the right critical dimensions and low runout, then there's no reason at all to jam in the lands. And there's an exception to even that equipment criterea, as seen with two bone stock factory rifles that shoot VERY well with an OCW load and a jump due to long throats.

If my mag box allows contact with the lands I like to start with at least a .015" or .020" jump...if I'm shooting TSX's then I automatically start with a .050" jump. One lesson I learned a few decades ago about bullet jump was with a stock Remington 700 chambered in 270 Win and the short little 90 grain Sierra HP. Reaching the lands was tough to do even with the big 150 and 160 grain bullets, and with the 90 it was impossible. That 90 grain bullet was THE best shooting bullet out of that rifle, and the jump to the lands was a whopping 250 thousandths of an inch....that's a quarter of an inch. It was one of those lucky golden nuggets of repeatable and dependable VERY sub MOA accuracy because it was at least 20 years prior to Dan's introduction of what we know as the OCW principles.

Jamming lands is an over rated myth, in my opinion......

 

[eracer]

Re: Knowing a bad node..?

Why oh why didn't I get into reloading 25 years ago?

It's so cool.

 

[timelinex]

Re: Knowing a bad node..?

Took the rifle to a distance and looks like for now I will be keeping the load, until further notice. Took it out as far as 990 yards. Unfortunately it was right before night time and we were in the middle of the desert, so by the time I got to the 990 yard target I only had time to fire 4 rounds before we had to pack up and go. First round was right on elevation wise but I underestimated the wind. One correction and the next 3 were on target. Here is the group it produced(the one big splash is a 338 hit):

I know 3 rounds is far from enough to call a load good. But it has gave me hope that this load might actually be the one. I will try to get out and do more long distance shooting sometime this month to confirm. Its hard considering I don't have a jeep , and all my spots are deep in the desert. Its not fun hiking 2 miles in 110 degrees with 80lb's of steel/rifles etc.. on your back.

Anyways, the one major thing I was astonished by is the predictability of this load. When I use to run SW ammo, they produced good accuracy but I always had a hard time getting it right on target elevation wise. No matter how much I tweaked the numbers, different distances didn't add up to produce accurate elevations. When I chronoed the load, even though the accuracy was good, the ES was around 30-40. When I chronoed my handload, my ES was 4. Which isn't fully accurate considering its less than the accuracy window of a chrono. But putting that number into the ballistics calculator put me dead nutz, elevation wise, on all the distances I tried. Even this 990 yard group was almost completely centered with no elevation adjusting. Not sure if the tiny ES had something to do with it or not but so far I'm liking it.

This is all just me thinking outloud, until I confirm with many more rounds! I just got a 24" piece of AR steel, which will be put out at a mile+. So I guess the mile will be the ultimate test for the load!