Speed increased, powder charge is the same.

918v

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Jul 15, 2007
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#51
I'm curious, because I really want to know how this works. Is that to raise or lower the pressure in the case - which will raise or lower the velocity?
It doesn’t raise or lower velocity, just gets your bullet back in the node. For example, if your node was at 2950 FPS with a spread of 10 FPS and now you’re at 2980 with a spread of 30, changing the oal will lower the ES by restoring the bullet/barrel harmonics sweetspot. You’ll find your velocity didn’t really change that much.

I think what happened in your case is your throat eroded and your bullet is jumping more. You might have had a marginal load to begin with and that little change in jump might have ruined it.

When I find a node I map it out by powder charge vs OAL. I find the middle of the oal range and the middle of the powder charge range and use the load where the two intersect.
 

260Girl

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May 16, 2018
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#53
It doesn’t raise or lower velocity, just gets your bullet back in the node. For example, if your node was at 2950 FPS with a spread of 10 FPS and now you’re at 2980 with a spread of 30, changing the oal will lower the ES by restoring the bullet/barrel harmonics sweetspot. You’ll find your velocity didn’t really change that much.

I think what happened in your case is your throat eroded and your bullet is jumping more. You might have had a marginal load to begin with and that little change in jump might have ruined it.

When I find a node I map it out by powder charge vs OAL. I find the middle of the oal range and the middle of the powder charge range and use the load where the two intersect.
Thanks for taking the time to explain that.

The load could have been marginal. The gentleman who re-barrelled the action told me to try that powder charge. I determined the OAL and loaded it. Up until now, it has been very accurate at matches, so I didn't see any reason to spend the bullets testing it.

Also, The barrel is about a third of the way through it's expected life, so some erosion could be possible too.

When you say that you found the middle of he powder charge range, do you do a ladder test within the node. (I read a SH post about that earlier). Or, do you do groups?

In my research about load testing, I've read that people test at 100, 300, 500 and even 1000 yards. What distance do you use?
 

918v

Manipulated by Variables
Jul 15, 2007
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#56
Thanks for taking the time to explain that.

The load could have been marginal. The gentleman who re-barrelled the action told me to try that powder charge. I determined the OAL and loaded it. Up until now, it has been very accurate at matches, so I didn't see any reason to spend the bullets testing it.

Also, The barrel is about a third of the way through it's expected life, so some erosion could be possible too.

When you say that you found the middle of he powder charge range, do you do a ladder test within the node. (I read a SH post about that earlier). Or, do you do groups?

In my research about load testing, I've read that people test at 100, 300, 500 and even 1000 yards. What distance do you use?
I do groups. My standard is half inch at 100 yards so I test in .1gr charge increments vs .005” oal increments until the groups open up. Ideally you want to have a broad range so that plus/minus .2gr/.010” maintains half moa. If that load’s velocity has single digit SD it doesn’t matter at what distance you test.
 

260Girl

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#57
I do groups. My standard is half inch at 100 yards so I test in .1gr charge increments vs .005” oal increments until the groups open up. Ideally you want to have a broad range so that plus/minus .2gr/.010” maintains half moa. If that load’s velocity has single digit SD it doesn’t matter at what distance you test.
Thanks for explaining that. What you said about the possibility of erosion made sense and Jay mentioned in his post that he did well with less jump with the 140 gr hybrids. I decided to try adjusting OAL (CBTO) first.

This morning, just for the heck of it, I adjusted the seating depth of 5 already loaded rounds. I seated them at .005 off the lands, which was .015 longer than what I've been loading.

These rounds were from a Lot that I've been shooting for the past couple of weeks. I needed to practice shooting a group @ 200 yards, so I used that distance.

The temp was slightly cooler and DA 500' lower than my last practice.
Here are the results:

Group 1 - 5 rounds, .020 off lands
Avg. MV 2724, SD 6.0, group size @200 yards was 1.25" - same as last week.

Group 2 - 5 rounds, .005 off lands
Avg. MV 2732, SD 2.8, group size @200 yards = .80"

I'm not back to where I was, but that appears to be an improvement. My groups at 100 or 200 yards use to be fairly uniform and would spread out pretty evenly as I took the rifle out to farther distances. Now at 100 yards, I have a 3- round .25, knot in the center, with 2 rounds in orbit on either side. At 200 yards it's a .5 MOA knot. I think I'll make a few more slight adjustments to the AOL, then make some slight powder adjustments.

I appreciate your help!
 
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Greg Langelius *

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Aug 10, 2001
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#59
A couple of things. There is great advice above.

If it were my situation, I would do a ladder test, 200yd is plenty for now.

I would also take note that Varget has been criticized many times in the past for varying performance from lot to lot. What I do with Varget is to keep track of lot numbers, and when the lot number changes, I do a mini load workup with charges just higher and lower as well as the normal charge, just to see if there's room for improvement with the new lot.

I am the resident fossil here, and I tend to take change slowly. I still hold group size as a valuable thing, especially when confirming an old load when components get changed, and that includes Varget lot numbers.

Varget is a good powder, but for my 260, I prefer H-4350. It may also be better with the 6.5x47. For me, Varget behaved as if it were faster than ideal with the 260 and 140's.

I started with the 260 in 2001/2002, and was using the 140SMK. When the 142SMK came out I went with the crowd, but the 140 remains a fine bullet, and can have advantages in semi's with its shorter length. I tried the 140 A-Max, and got flyers. When they brought out the new AMP jacket, I tried the A-Max again and the flyers had gone away. Now, I'm testing the 143 ELD-X, and things are bogged down with outside issue; for instance, my Wife just came home from hospital following an accident where burns are involved. She's doing great, but right now she's pretty helpless/immobile, and while I definitely don't mind, keeping up with her takes much time.

Lot numbers are important with bullets, too. When I started getting flyers with same size main groups, the issue tended to follow bullet lot numbers. I wouldn't just blindly rule out bullets, they are more highly suspect, IMHO, when things tend to go sidewise without some other glaring reason. Bullet manufacturing is an industrial process with machine setup and parts wear-out being critical to bullet quality. We all watched when the Lake City 173 match bullet quality slowly augured in on its nose due to lack of production machine maintenance, ushering in the switch to 175SMKs by Uncle Sugar. That's a large part of why seconds become available from time to time. Seconds are different, and we seldom get to know how or why. Factory QC is usually way good enough for the likes of me, but YMMV (Your Mileage May Vary...).

For example, a thousandth or two increase in bullet diameter can boost velocities, and if it's not absolutely consistent, can also throw out flyers.

Bench marking can work both ways. For example, I just got a bunch of IMI 168 Semi-Auto Match from Midway to try out. I will be running it against a 168gr match load of mine in a heavy barrel bolt gun, just for giggles and such. If it works well enough, I may not need to handload for the 308 after this. At age 72, time is more than money.

Greg
 
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260Girl

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#60
People have been really helpful and have posted some good information. Many thanks to everyone who responded.

As I understand it, Varget can produce a lot of fouling. I've ordered something to use on my bore in case I have a carbon build up.

One suggestion was that the heat/temperature increase may be a factor. I'm looking at that as well.

As far as components go - I've learned that they are a lot more variable than I realized, and that it's a good idea to keep data on individual lots, so I can tell if a change in my ammo can be tracked to a change is a specific component.

I've noticed changes with Varget from lot to lot, too. I used IMR 4350 for my .260, but never considered it for my 6.5 x 47. At this point I'm going to stay with Varget.

Thanks for the suggestion to do a ladder test at 200 yards. I'll keep that in mind as I move forward with adjusting my load.

I'm finding it to be true "that time is more than money". Also, that I like to shoot better than I like to load. And, that I can wear out a barrel really fast trying to find a "perfect load".

Thanks Greg.
 
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Greg Langelius *

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#61
Welcome.

I see the .260 as somewhat under powered when compared to its perennial rival, the 6.5-284. But of the two, I choose the 260 because of bore life. And now, I see the 6.5CM as being somewhat less (which is somehow being represented as more). And then, there's the 6.5x47, which I find as quite intriguing despite even less case capacity. I've seen it do remarkable things at 300yd, and wondered whether it's a genuine 1000yd capable cartridge. Looks like it is.

As for Varget vs H-4350, I agree, now's not the time to change horses in midstream.

But downstream...? According to the Hodgdon site, in the 6.5x47, H-4350 produces the highest listed velocity.

200yd vs 100yd testing for LR chambering demonstrates vertical dispersion better than 100yd, while still keeping the effects of wind down to a manageable/understandable degree. That vertical dispersion relates to things a chrono can tell you, but I don't own one. My target is my chrono.

Almost any powder can produce exaggerated fouling up until the pressure level gets significant. Carbon fouling is (IMHO) what's left of kernel coatings after combustion. Traditionally, those coatings have been graphite, which is coincidentally a dry lubricant. Coatings are evolving, and my intuition suggests they may be in some way related to moly. When folks bring moly to the table (er, bore...), I consider it to be an added complexity in the bore velocity/bore friction/pressure/velocity equation. We already have our dry lube in the form of 'carbon' (graphite) fouling. Anything which reduces bore friction in turn reduces pressure, and in turn reduces velocity. Bore fouling status bears directly on velocity, and is why a clean bore needs fouling to deliver a steady POI. Bore pressure is better when it's up there (but not peaking), in order to ensure that the fouling is mostly, if not all, the residual kernel coating. If I thought moly was a valuable complication, I would mix it with my powder, not plate it onto my bullets.

If I sound like I like hot loads, I don't; I think they do only a few things, like burning up barrels and blowing up guns. Metal fatigue is reality, as is Mean Time Between Failures (MTBF). Velocity does not conquer wind, good shooting skills do that; and cranking up the velocity is just a tempting illusion.

Confused yet?

The complexities can be confusing until one takes a step back and applies the scientific method. Accept that there are complexities, but also that they work fine together until we start manipulating the individual factors.

Doing so with a method is called experimentation, without the method, it is just shooting in the dark. If I'm going to do manipulation, it will be about removing individual factors, and not about slipping additional ones into the melee. Removing a factor reveals the consequences of the factor's presence, and putting it back in confirms the conclusions. Once we know the consequences, with and without the factor, we can try substitution, and gain more insight. Reintroducing the original factor in combination with the new factor reveals whether they are compatible, i.e. whether the new factor helps or hinders.

I'm not talking about your issue right now, but about issues in general.

The point is that this stuff is a long game. The other point is that, like you, I am mindful of bore longevity. Maybe too mindful, but that's just me.

Keep your experiments down to altering only one factor at a time. It's tempting to skip the middle stuff, but if we do, we really don't know which alteration makes which outcome a reality. The time to combine factors (components) is at the beginning, and provides the whole foundation for the experiment. When the experiment fails to achieve progress, it usually means that the initial foundation is non-supportive.

Make your experiments statistically meaningful. Three round groups are occasionally thrilling, and statistically meaningless. Five round groups show coarse trends, but are not conclusive. Twenty round groups are very revealing, but hard on the bore. You have to weigh all of these alternatives. Once you 'have' your solution, test it rigorously before committing to volume ammunition production.

Stay the course, finish a sequence of test regardless of how intuition pesters you. Without a full data set, the experiment is flawed. Accept that barrels are a 'wear item' and that what you are doing is more about testing than about competitive achievement. Share your results and you will usually learn more from the sharing. In order to save barrels, you usually need to burn barrels initially. Careful/judicious test design and experimental discipline can keep that necessary bore wear down to the minimum.

The human memory being what it is, take notes; complete notes; and follow up your conclusions with a journal.

Greg
 
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260Girl

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#62
Pearls of wisdom, Greg. Thank you!

I am currently shooting the 6.5 x47, which for me is very 1000 yard capable, but I am working on putting together another .260 just because I like the caliber. No scientific basis... I just like the way it shoots!
 
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mijp5

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May 7, 2009
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#66
3 shot groups have caused me a lot of trouble in load development. Even in situations where a 3 rd group would appear to be a good gauge, it has made me waste a whole lot of time. But still, a bad 3 rd group should rule out a load
 
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260Girl

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#67
3 shot groups have caused me a lot of trouble in load development. Even in situations where a 3 rd group would appear to be a good gauge, it has made me waste a whole lot of time. But still, a bad 3 rd group should rule out a load
Based on my experience with a load for a different rifle, 3 shot groups did help me rule out a oal/powder charge, so in that respect I have found them helpful. I also had them cause trouble, so that's something for me to keep in mind. Thanks for the reply.

With this 6.5 x 47 load, I currently have a flyer in a 3 shot group, and 2 flyers in a 5 shot group, so I think a 3 shot group will be helpful at this point.
 

supercorndogs

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Feb 17, 2014
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#68
There is going to be some variation from shot to shot, even with the same powder charge. Aside from a possible change in the chronograph function, you would have to shoot something like 30 to 40 rounds of each charge weight to have good confidence that you were getting a useful average.

If this wasn't in the exact same shooting session, a slight change in the angle you were shooting over the chronograph may change the distance that the bullet travels over the screens.
The screens on her magneto speed? I think you are in over your head here, and you should be reading and learning from some of these posts. Not just going to the bottom and commenting with out reading the thread.
 

260Girl

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#69
Well you narrowed it down to yourself or a finicky rifle that acts like an off the line 700. Get some Match grade ammo and keep it on hand as a benchmark. Or check your aiming parts and make sure your bipod is on tight. Why does everybody think the load they wasted all that time on suddenly went to shit? Make sure all your shit is wired tight.
Well you narrowed it down to yourself or a finicky rifle that acts like an off the line 700. Get some Match grade ammo and keep it on hand as a benchmark. Or check your aiming parts and make sure your bipod is on tight. Why does everybody think the load they wasted all that time on suddenly went to shit? Make sure all your shit is wired tight.
One suggestion posted was to use a bore cleaner for carbon, in case I had a carbon ring causing increased barrel pressure. I did this, but didn’t see any improvements in my group accuracy. Remembering what you suggested about making sure everything was tight, I checked the action screws. They were not tight. The front one turned with almost no effort at all. I torqued them to 45 in. lbs. and... no more flyers!

My barrel is still faster and my groups not as tight, but I can tweak the load if I need to. The important thing is that I got rid of the flyers!

Thanks for the suggestion Culpeper!
 
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