Help with ladder test

[Jager]

It's curious that your load using virgin brass was notably and consistently better than that same brass once-fired. Usually we expect to see a modest improvement as fired brass fire forms to the chamber.

The once-fired brass that you're now working with - is that the same lot of brass that you saw 1/2 MOA from previously?

Same lot of powder? Same lot of bullets?

You've got a solid body of experience with that load in that rifle - 400 rounds is a compelling statistical sample. Given that long experience, I'd be inclined to re-run your ladder. And I'd load enough rounds to do it twice (cleaning the bore between each 21-shot segment - I'm including three foulers). I would pay attention to velocity - because that gives you a proxy into what kinds of pressures you're running - but would mostly ignore ES until you're dialed back into a load that is starting to look interesting.

Have you confirmed the amount of shoulder bump you're getting when you FL size?

QuickLoad shows a preliminary print (preliminary because it's using all program defaults) of 2914 fps with the 215gr Berger Hybrid out of a 26" barrel, with 78.0/RL-26. So it's in the neighborhood of what you're seeing.

 

[RegionRat]

isnt dod the same people that paid $300 for a HAMMER AND $500 FOR A TIOLET SEAT. i would not be using that life as a reference for the real world.

The "$500 Hammer" was an instrument that contained a piezoelectric force sensor for modal analysis testing.

It would have cost anyone else $800, but the Gov caught a break. Leave it to some "wet behind the ears" politicians to distract the public with BS, while the real waste went un noticed right in front of them.

The "toilet seat for $300" was a $100 custom airplane seat that includes $200 worth of paperwork because we have to let all the government bureaucrats in Richmond participate.

But fear not, the Clinton Administration kicked all the standards bodies out of the DoD and forced them into the ASTM and SAE. Everybody knows that an international committee gives a S@#T about the DoD's problems and America's defense industry capabilities. Enjoy your "real world" as you watch the standards and quality of life go down the tubes. YMMV.

 

[leclairk]

To answer a few questions; This is the very beginning of my load development process. I loaded all rounds at .03 off because that seemed to work well last time. My next step was to start playing with seating depths.
Neck tension; this is something I’m not totally clear about. I have a Whidden FL bushing die with a .333 bushing. One of my loaded rounds measures .336, so my neck tension would be .003? If I’m going to play with neck tension then I would need to buy multiple sizes of bushings to put in the die (not sure I want to spend the money on that). It did come with a .335 bushing so I have one of those.
All components I used for this test were the same lot numbers (bullets, brass, powder, primers). Shoulders on virgin ADG measures 2.192, one fired brass measures 2.192 so I did not bump the shoulder, only fl sized.
Given that I’ve got a node in the low 77’s, I may play with seating depths in that area just to see what happens. If I can’t get any decent groups then I’ll be forced to play with it other factors.

 

[INTJ]

The "$500 Hammer" was an instrument that contained a piezoelectric force sensor for modal analysis testing.

It would have cost anyone else $800, but the Gov caught a break. Leave it to some "wet behind the ears" politicians to distract the public with BS, while the real waste went un noticed right in front of them.

The "toilet seat for $300" was a $100 custom airplane seat that includes $200 worth of paperwork because we have to let all the government bureaucrats in Richmond participate.

But fear not, the Clinton Administration kicked all the standards bodies out of the DoD and forced them into the ASTM and SAE. Everybody knows that an international committee gives a S@#T about the DoD's problems and America's defense industry capabilities. Enjoy your "real world" as you watch the standards and quality of life go down the tubes. YMMV.

Also, the $400 flashlight was an aircraft emergency exit light that was usually powered by 28 VDC from the aircraft electrical system. In the event of a 3g sudden deceleration of a loss of 28 VDC power, the lights would illuminate and be powered by the back up batteries--think they were four D Cells. Also, each light could be easily taken from the plane and operated off its batteries.

The $800 coffee maker was a commercial grade coffee maker that operated off the aircraft electrical system and was designed to stay in place in the event of a crash.

 

[Webster]

isnt dod the same people that paid $300 for a HAMMER AND $500 FOR A TIOLET SEAT. i would not be using that life as a reference for the real world.

I think they paid $15,000 for the golf club they took to the moon. Heard stories of troops ordering ordinary batteries from the US and they were shipped from a military warehouse in Germany for about 10X what they cost in the US.

 

[Jager]

To answer a few questions; This is the very beginning of my load development process. I loaded all rounds at .03 off because that seemed to work well last time. My next step was to start playing with seating depths.
Neck tension; this is something I’m not totally clear about. I have a Whidden FL bushing die with a .333 bushing. One of my loaded rounds measures .336, so my neck tension would be .003? If I’m going to play with neck tension then I would need to buy multiple sizes of bushings to put in the die (not sure I want to spend the money on that). It did come with a .335 bushing so I have one of those.
All components I used for this test were the same lot numbers (bullets, brass, powder, primers). Shoulders on virgin ADG measures 2.192, one fired brass measures 2.192 so I did not bump the shoulder, only fl sized.
Given that I’ve got a node in the low 77’s, I may play with seating depths in that area just to see what happens. If I can’t get any decent groups then I’ll be forced to play with it other factors.

Experimenting with bullet seating depth will likely gain you something. But if it were me, I'd hold off on making any of those changes until I figured out what has gone sideways with my present load. Having a 1/2 MOA load (with virgin brass) double in size simply because you sized that now once-fired brass is, well, unusual.

And if the only thing different is the FL resizing itself, that's where I'd look.

A virgin piece of brass, loaded and fired one time, is not fully fire-formed. But the shoulder has moved. It's perfectly fine to deliberately avoid bumping the shoulder another firing or two, awaiting a completely fire-formed piece of brass (but risking getting into the area where closing the bolt on some rounds becomes stiff). But if that's what your goal is, I'd suggest neck sizing. Understand that when you FL resize, without controlling the shoulder, the brass has to go somewhere. Typically, it pushes the shoulder out.

It'd be my guess that that's where your problem lies.

 

[leclairk]

Experimenting with bullet seating depth will likely gain you something. But if it were me, I'd hold off on making any of those changes until I figured out what has gone sideways with my present load. Having a 1/2 MOA load (with virgin brass) double in size simply because you sized that now once-fired brass is, well, unusual.

And if the only thing different is the FL resizing itself, that's where I'd look.

A virgin piece of brass, loaded and fired one time, is not fully fire-formed. But the shoulder has moved. It's perfectly fine to deliberately avoid bumping the shoulder another firing or two, awaiting a completely fire-formed piece of brass (but risking getting into the area where closing the bolt on some rounds becomes stiff). But if that's what your goal is, I'd suggest neck sizing. Understand that when you FL resize, without controlling the shoulder, the brass has to go somewhere. Typically, it pushes the shoulder out.

It'd be my guess that that's where your problem lies.

I will give that a shot. It just seemed strange to me that I would bump a shoulder past what the virgin brass was.

 

[Ned Ludd]

An Audette ladder test and Dan Newberry's OCW group-based method are essentially looking at the same phenomenon, which is the effect of increasing charge weight on bullet POI for a single shot (ladder test), or the centerpoint of a three-shot group (OCW). There arew some rather subtle differences between the two test, such as that ladder tests are typically carried out at longer distances to create better vertical separation of the shots on the target, and charge weight "nodes" are identified as two or more increasing charge weights in a row that generate consistent vertical POI on the target. In an OCW test, one looks for two or more increasing charge weights in a row that generate a consistent POI for the centerpoints of three-shot groups around the POA. (i.e. the centerpoints of the groups don't move about the POA as charge weight increases). This type of test can easily be interpreted at distances of only 100 yd.

It is merely semantics to state that a ladder test isn't a ladder test because three-shot groups were used. It is not uncommon for people to shoot multiple single shot ladder tests side-by-side, as a means to provide stronger statistical support for any conclusions that may be drawn from the test (i.e. the confidence is better if two or three ladder tests shot side-by-side all look exactly the same). Is there really any difference between three identical ladder tests fired side-by-side and a single ladder test where all three shots were on the same target? I don't think so. As long as one can correctly associate each bullet hole with the loaded round from which it originated, there is no difference between the two.

For the OP - as far as how to proceed from here, you could certainly repeat your testing within the charge weight region you have identified as being of interest, except using a smaller charge weight increment such as 0.1 or 0.2 gr. That may allow you to fine tune optimal charge weight and load to the center of the optimal charge weight window a little better. Alternatively, because this testing was carried out with virgin brass and you know you will likely have to alter the load to some extent after the brass is fire-formed, you could also probably just use the charge weight you have identified and proceed with seating depth testing to potentially shrink the groups a bit further.

 

[leclairk]

Experimenting with bullet seating depth will likely gain you something. But if it were me, I'd hold off on making any of those changes until I figured out what has gone sideways with my present load. Having a 1/2 MOA load (with virgin brass) double in size simply because you sized that now once-fired brass is, well, unusual.

And if the only thing different is the FL resizing itself, that's where I'd look.

A virgin piece of brass, loaded and fired one time, is not fully fire-formed. But the shoulder has moved. It's perfectly fine to deliberately avoid bumping the shoulder another firing or two, awaiting a completely fire-formed piece of brass (but risking getting into the area where closing the bolt on some rounds becomes stiff). But if that's what your goal is, I'd suggest neck sizing. Understand that when you FL resize, without controlling the shoulder, the brass has to go somewhere. Typically, it pushes the shoulder out.

It'd be my guess that that's where your problem lies.

Now that you mention it, I did have some rounds where the bolt was a little stiffer to close. Could that explain some of my high ES numbers and poor groups?
Also, can I resize the cases I already sized or should I use new 1x fired cases and size those?

 

[Sniperhandle]

Loading 300PRC, 215gr Bergers, RL 26, ADG Brass, .03 off lands, 3 shot groups, none of the groups were particularly good (about 1 MOA)
76.5gr- av 2926 fps, ES 27.5
76.8gr- av 2972 fps, ES 44
77.1gr- av 2970 fps, ES 20
77.4gr- av 2978 fps, ES 14
77.7gr- av 3010 fps, ES 11.5
78 gr - av 3016 fps, ES 7.7
I had loads at 78.3 and 78.6 but I started getting nervous with those velocities at 78gr. I saw no pressure signs other than a very slight stiff bolt. Looks like a node at 77ish but the ES is not that great. I like ES at 77.7-78 and the velocities seem consistent. How do you think I should proceed? Also interesting to me that my ES continues to drop as my charge increases.

By the time you get a "Light Stiff Bolt Lift" You are way over pressure. Look at your brass for ejector hole imprints and or swipes.

 

[Jager]

Now that you mention it, I did have some rounds where the bolt was a little stiffer to close. Could that explain some of my high ES numbers and poor groups?
Also, can I resize the cases I already sized or should I use new 1x fired cases and size those?

Yes, you can resize the cases you already sized.

Three things might cause a stiff bolt close: a bullet seated too long such that it's jammed hard into the lands; a base-to-shoulder dimension that has reached the chamber dimension; or insufficient sizing of the case head area (not very common, but the reason small-base dies exist).

Based on your comments, I'd guess you probably have some kind of shoulder bump issue. I wouldn't normally expect that to lead to a doubling of group size. But when you look at what you've got... a 400-round history with a given load in a given rifle... and the only thing you've now changed is that you are FL sizing your brass... leads me to think there's something amiss in your die setup.

The other thing, though... you've run only one ladder, and you have what amounts to a single 3-shot group (at your previous charge level) that isn't meeting your expectation. So on the one hand you've got a 400-round history that tells you to expect 1/2 MOA. And on the other, you've got a single 3-shot group which came in at double that.

There are a million reasons why a single 3-shot group might come up wanting. And so I wouldn't conclude too much from it until you have more samples.

If it were me I'd have a single expectation above and beyond everything else: that the 1/2 MOA performance I saw with my load using virgin brass over 400 rounds, will continue at least that good over the next 400 rounds, using the same brass, only now having FL resized it.

And so the first thing I'd do is load some more of that exact same load, only FL sized of course, and see what it does. Shoot a bunch of those 3-shot groups.

Repeat the ladder if you want. Or run a tighter ladder focusing on smaller charge increments just before and just after your old load's charge level.

It does sound like you have sizing issues. I'd go back to square one, resetting and remeasuring everything. There's not a one of us here who hasn't messed up a die setup at some point, so don't feel bad about it. Just make sure you and your calipers become real good friends.

Keep us posted.

 

[JFrank]

Now that you mention it, I did have some rounds where the bolt was a little stiffer to close. Could that explain some of my high ES numbers and poor groups?
Also, can I resize the cases I already sized or should I use new 1x fired cases and size those?

That should not effect the ES at all.