Multiple Nodes Vs. Seating depth relationship.

[Rh0dz]

I currently have a 6.5cm load that shoots lights out. Problem is it's just shy of meeting the power factor for NRL Hunter. Im running 140 bergers at 2680.

I attempted load development this time by looking for optimal seeing depth first, then fine tuning with powder. As I've read, most rifles have an lower and upper accuracy node. Question, is seating depth typically constant regardless of upper or lower powder node? For you that start your load dev. with seating depth, what is your process? I've read the Burger VLD process but wonder what others are having success with.

Load:

Berger LR Target 140s
Lapua brass (virgin)
#450
H4350 40.7gr
.057 jump
2680 ft/sec

 

[Rh0dz]

 

[Conrad]

I think you can bump up 0.5 gr at a time pretty easy and see what it does around 42 gr. My 24” barrel does 2750 with 144 LRHTs and 42 gr H4350. Shooting 50 thous off.

 

[straightshooter1]

I currently have a 6.5cm load that shoots lights out. Problem is it's just shy of meeting the power factor for NRL Hunter. Im running 140 bergers at 2680.

I attempted load development this time by looking for optimal seeing depth first, then fine tuning with powder. As I've read, most rifles have an lower and upper accuracy node. Question, is seating depth typically constant regardless of upper or lower powder node?

No.

For you that start your load dev. with seating depth, what is your process? I've read the Burger VLD process but wonder what others are having success with.

From the Berger website:

Load 24 rounds at the following COAL if you are a target competition shooter who does not worry about jamming a bullet:
1. .010 into (touching) the lands (jam) 6 rounds
2. .040 off the lands (jump) 6 rounds
3. .080 off the lands (jump) 6 rounds
4. .120 off the lands (jump) 6 rounds

Load 24 rounds at the following COAL if you are a hunter (pulling a bullet out of the case with your rifling while in the field can be a hunt ending event which must be avoided) or a competition shooter who worries about pulling a bullet during a match:
1. .010 off the lands (jump) 6 rounds
2. .050 off the lands (jump) 6 rounds
3. .090 off the lands (jump) 6 rounds
4. .130 off the lands (jump) 6 rounds

Shoot 2 (separate) 3 shot groups in fair conditions to see how they group. The remarkable reality of this test is that one of these 4 COALs will outperform the other three by a considerable margin. Once you know which one of these 4 COAL shoots best then you can tweak the COAL +/- .002 or .005. Taking the time to set this test up will pay off when you find that your rifle is capable of shooting the VLD bullets very well (even at 100 yards).

Berger LR Target 140s
Lapua brass (virgin)
#450
H4350 40.7gr
.057 jump
2680 ft/sec

Keep in mind that whatever one's jump is, it doesn't tell anything about seating depth because:

. . . different comparator inserts used for jump measurements vary where there can be as much as .040 or more difference.

. . . different chambers have different dimensions. Like, one might have a chamber with a freebore of .167 while someone else's freebore might be .221 or maybe .124 and the .057 jump would be a very different seating depth between those chambers.

It's better to inform about COAL to get a better idea of how a cartridge is actually set up (even though there some variation in bullets OAL).

 

[Conrad]

That’s cool and all but it’s a 140 hybrid…..bump your charge, meet PF and go shoot.

 

[Doom]

I would look to get the load up to about 42 gr with your current seating. But that is well above some max loads so I don't know if you can get there. Should get you about 60-70 fps. The other option is to decrease the COAL along @straightshooter1 recommendations. Also, I would expect about 20-30 fps higher velocity with resized fired brass.

 

[Rh0dz]

I would look to get the load up to about 42 gr with your current seating. But that is well above some max loads so I don't know if you can get there. Should get you about 60-70 fps. The other option is to decrease the COAL along @straightshooter1 recommendations. Also, I would expect about 20-30 fps higher velocity with resized fired brass.

I went up to 42.5 today with Lapua srp virgin brass and had zero pressure signs. Groups opened up a bit. I guess I'm going to push it some more in .2 grain increments and see if I can get a higher node.

 

[Aftermath]

I shoot VLD's almost exclusively but I do load development the same for whatever style bullet. I go about the load development a little differently and it does work (for me). I start with the bullet just shy of the lands by 0.002" or just barely touching. I start with the minimum recommended charge weight and load 5 rounds, shoot, look for pressure signs, checking velocity and such. Then I increase the charge weight by a half grain and load 5 rounds, shoot and look for pressure signs and such. Repeat until I do see indications of pressure and go back down to the previous charge weight.
Then I start seating the bullet deeper into the case and look for some accuracy "nodes", ignoring velocity. I will choose the one that is closest to the lands and check velocity again. Then I do the next accuracy node and check for velocity again. Repeat if you have another sweet spot.
Then I test for more charge weight at those accuracy spots just in case I can get more velocity safely and still have acceptable accuracy. The vast majority of the time, if I increase the velocity, the accuracy suffers and I have to do a seating depth search again. Usually I go ahead and do that because I like velocity as long as it doesn't hurt the accuracy. I'm not restricted to some velocity because I'm not going to go shoot that NRL Hunter.
As stated above, find that PF that works for your 140's by increasing your velocity. Then find a seating depth that settles in for your rifle.

 

[Jack's Dad]

Going higher than 42.5 seems a bit crazy. I'm 41.5 mag length brand new 24 inch barrel getting 2810 fps.

 

[kthomas]

I'm not sure what velocity you would need to make power factor, but I would do a velocity ladder to see what charge weight gets you in to the needed PF without getting any pressure.

From there, I would load up some ammo with that new charge weight and see how it shoots. I wouldn't change anything except charge weight at first.

 

[spife7980]

I'm not sure what velocity you would need to make power factor

380,000pf/140gr=2,714 fps

 

[kthomas]

380,000pf/140gr=2,714 fps

Should be no problem to achieve that with a slight CW bump

 

[spife7980]

I went up to 42.5 today with Lapua srp virgin brass and had zero pressure signs. Groups opened up a bit. I guess I'm going to push it some more in .2 grain increments and see if I can get a higher node.

You were at 2680 with 40.5gr but with 2 more grains you still havent hit power factor at 2715 fps and are still looking for more speed?
How fast was 42.5 for you?

With my experience of lapua brass, 4350 and 140 rdfs you are real close to hitting some pretty substantial pressures there.

 

[Rh0dz]

You were at 2680 with 40.5gr but with 2 more grains you still havent hit power factor at 2715 fps and are still looking for more speed?
How fast was 42.5 for you?

With my experience of lapua brass, 4350 and 140 rdfs you are real close to hitting some pretty substantial pressures there.

42.5 was 2810ish. Well into power factor but am chasing a group similar to what's at the lower charge.

 

[Doom]

42.5 was 2810ish. Well into power factor but am chasing a group similar to what's at the lower charge.

How may 3 shot groups are like that?

 

[CK1.0]

Don't mean to crash in anyone's rifle reloading lore/mythology party... but why are you assuming your lower powder charge (or any other powder charge really) has anything to do with the size of your groups? That's only one single variable, and unless you're locking your gun into a fixed mechanical rest and actuating the trigger electronically or something, and putting calipers and micrometers on every single other little detail, then there are quite a few other variables going on that could've affected your results. Not to mention, shooting 3 or 5-shot groups can make things even murkier since that's not really a reliable/useful sample size (shoot and compare 2 different 20-shot groups of your current best/worst loads and I bet they'll look eerily similar).

It's more important to make each and every round as exactly the same as you can... versus, how many grains of powder or how many thou off the lands you are. You could even come up with a "bad load" and if each and every round you make has powder dropped to the kernel and you can seat all your projectiles to within a couple thou, it will shoot... and miraculously/coincidentally, you'll have found one of those mythical nodes that exist on shooting forums and in some guy's heads, but not in the natural world.

Just figure out how many grains of powder it takes to hit 2714fps, load all your bullets to the beginning of a jump range where the average group size does not change much and will not be affected as the throat erodes (or simply choose the longest jump that shoots from the start), done.

 

[spife7980]

Ah yes, the “load development is a lie” theory where everyone else in history is wrong about their first hand results.

 

[Rh0dz]

I appreciate everyone's feedback. Hand-loading is obviously not an exact science and there are multiple avenues to achieve successful results. My main question was for those who start load development with testing various seating depths at a mild or low charge when shooting a new caliber. I'm newish to reloading and mostly am interested in feedback from those who have found multiple velocity "nodes" for their rifles. Did they both shoot well with the same or similar seating depth? Or, did you have to tweak seating depth again for higher/lower velocity nodes.

I'm approaching load dev. from the perspective that seating depth is the macro adjustment and using powder to fine tune the optimal jump distance. I am finding this to be true as while shooting virgin brass I had several of the brass with loose neck tension and the bullets were seated .003-.004 deeper then the others and the POI shifted much more then with the powder charge change.

 

[Rh0dz]

Here is an example of loose neck tension or a thinner bullet that seating .004" deeper. The POI shifted to 7:30

 

[CK1.0]

Ah yes, the “load development is a lie” theory where everyone else in history is wrong about their first hand results.

More like “load development is a Rorschach test” (for a lot of guys anyways).

Much of the lore/mythology dictates guys burning up their components looking for some perfect recipe… when they should probably admit they don’t always shoot every single group as well as the last/next (the human is the biggest variable), and they might just be better off saving for a more precise scale so all of their drops are as exactly the same as possible.

More/less fuel = more/less speed, always. There are no “nodes” or “flat spots”, if it looks like there are, then that just means the sample size is too small to see it, and one hasn’t shot enough groups to recognize that they’re seeing what they want to see.

 

[diggler1833]

In part, I want to agree with the above statement. I certainly don't shoot with the same level of proficiency from day-to-day. That being said, I also don't expect to see much deviation in group size on a consistent load either if I'm firing from a stable position.

I do however believe in charge weights were some ES and SD will tighten up, and found that it usually corresponds with case fill. I also believe in *mild* velocity flat spots where velocity does go from being pretty linear in correlation to charge weight, to having a lesser/greater affect for a certain range.

Does that mean I believe you'll see a wild swing in accuracy with a slight charge weight and seating depth adjustment? Probably not, but there are exceptions and I own a barrel that is one of those.

Everything has an effect on the tuning fork that is our barrel. Sometimes it is inconsequential if we are lucky, sometimes we just get cursed with a picky barrel.

We will forever argue on how much effect someone is going to observe based upon our own observations with our own unique sample set...which is stupid if going beyond a generalization. Show me where someone has it nailed down, and I'll show you someone who gets fantastic results doing it a different way...and they'll inevitably end up on here pointing fingers at each other and saying the other is stupid.

 

[straightshooter1]

I'm approaching load dev. from the perspective that seating depth is the macro adjustment and using powder to fine tune the optimal jump distance. I am finding this to be true as while shooting virgin brass I had several of the brass with loose neck tension and the bullets were seated .003-.004 deeper then the others and the POI shifted much more then with the powder charge change.

I would say that shift you got was not due much to the deeper seating depth, but mostly due to the "loose neck tension". Neck tension is a significant factor in developing a good load. It's something that needs to be worked out just as seating depth. Above all, it needs to be consistent.

 

[Rh0dz]

I would say that shift you got was not due much to the deeper seating depth, but mostly due to the "loose neck tension". Neck tension is a significant factor in developing a good load. It's something that needs to be worked out just as seating depth. Above all, it needs to be consistent.

Understood. I punched out the virgin brass w/ a mandrel and a few pieces were looser than the punch out diameter. I just shot them to fire form the brass, but point taken.