Load Development Help/Opinions

[cornchuck]

I have been working up some loads for my Christensen Arms Mesa 300 PRC with a 1:8 twist barrel. I think I have found something that might work. Barnes 200 LRX with H1000. I had been doing a slight different version of a OCW test. I start my testing almost at minimum, 70.0 grs., and work up in .5 gr. to 75.5. At 75.5, I could hear some crunching as I was seating the bullet. Barnes says min is 69.4 (2644fps) and max is 77.1(2891 fps). I loaded these at book length which is 3.500". Which is about .10" shorter from mag length. Take a look at the attached target. I think I know which load I want to work on. Just want some opinions on what you see. Plus, I'm wondering if it's fast enough for what I am shooting. I haven't ran these through my Magnetospeed so don't know how fast they are. Usually find that after I find a load.

Jason

 

[RB II]

If 73.5 is three bullets in two holes looks like you have a node there between 73 and 74 gr. Maybe try .2 gr increments between 73 and 74. Pick the best of those and work on seating depth/jump.
Were you able to measure the chamber for total length/how much jump does this target reflect? If there is room to load the bullet longer, you might find a good node in one of the other loads also. And will afford more space in the brass to stop the compressed load issue. Maybe load the seating depths at 5-15 thou apart to hunt down the best depth for that bullet in that barrel. Refine from the best of those.

 

[Dmagna]

hard to tell what's going on here without chrono numbers. Could have huge inconsistencies in numbers, don't know.

 

[The_Whitetail_kid]

73 grains is solid group. Play with seating depth
A little and see if it tightens

 

[MagnumManiac]

Load number 7 is the only one I see with any potential.
In fact, I would be worrying about seating depth before I even contemplated a powder charge.
I would work on seating depth with that charge then fine tune powder/primer.

Cheers.

 

[Tiny Tim]

Agree with RB II, the poi is the same for the groups from 73-74 grains. I might start at 72.7 and work up in .3 grain increments. That said, I generally do seating first. As far as the compressed loads, did you try a drop tube or vibrating to settle the powder prior to seating the bullet?

 

[Lonewolf74]

Just a few thoughts and observations. You stated your seating the bullet at book length which is .100 shorter than magazine length, any idea how far off the lands you are? Those bullets could be jumping a long ways which isn't necessarily bad but could be much more accurate somewhere else. So as others have said I would figure out where the lands are and basically do an OCW with seating depth. Or you could just load to max mag length and work back to your current length. For example pick any random charge weight and load 3-5 at 3.600, 3-5 at 3.580, 3-5 at 3.560 etc.

Remember OCW is finding a node based on the same point of impact through a few charge weights. It does look as though you have a very wide node from 73-74.5 grains and I would work in this area after finding the most accurate seating depth.

 

[Beluebow]

I like 73-73.5...POI is moderatly stable and it's wanting to dot up. 74.0 it's starting to move out and get big fliers IMO.

 

[Zen Archery]

73-73.5 looks good to me too…

 

[Pudgy]

I have been working up some loads for my Christensen Arms Mesa 300 PRC with a 1:8 twist barrel. I think I have found something that might work. Barnes 200 LRX with H1000. I had been doing a slight different version of a OCW test. I start my testing almost at minimum, 70.0 grs., and work up in .5 gr. to 75.5. At 75.5, I could hear some crunching as I was seating the bullet. Barnes says min is 69.4 (2644fps) and max is 77.1(2891 fps). I loaded these at book length which is 3.500". Which is about .10" shorter from mag length. Take a look at the attached target. I think I know which load I want to work on. Just want some opinions on what you see. Plus, I'm wondering if it's fast enough for what I am shooting. I haven't ran these through my Magnetospeed so don't know how fast they are. Usually find that after I find a load.

Jason
View attachment 479395

Everyone has their method. But here's mine.

1) I work on the powder/bullet combo. Im looking for a stable node with low Sd/ES.

I would work in .4 to .6 increments, when you find something to explore, you can come back and shoot the .2 or .3 between the .4/.6. IE say you do .6 and like a node between 65.2-65.8 come back and shoot 65.5. Now you have data for the whole range.

target is not really needed, but can provide useful data, chronograph is required.

2) Once I find the powder/ bullet, I test for best primer. Again target not needed, chrono is.

3) do seating depth test. Preferably at 600 yards. But can be done closer.

The seating depth is to tune your load, or change the timing when it exits the barrel. Closer to the lands it exits faster, and pressure/speeds will be faster, farther from the lands, not only does it exit slower, but speeds will also decrease.

it serves no purpose to tune the load and then do your powder and change everything up. You'll end up chasing your tail.

Here's a picture of one of my seating tests. Lost 15 fps, but found a wide seating node that should stay tuned for the life of the barrel.

But…..your not done yet. Now to take it out to distance and verify the load.
Shoot in different weather, ect.

I just had a "great load" fall apart at 1,000 yards in 95 degree weather. Because I skipped the primer test.

Last night I did the primer test in 95 degree weather on 7SAUM/180hybrid.

26 rounds in 15 minutes over .5 grains of powder, combined SD 6.3 - ES 23 and that's with a barrel that was at 159 degrees at the end of the test.

hope this is helpful in someway.

 

[cbuck516]

Everyone has their method. But here's mine.

1) I work on the powder/bullet combo. Im looking for a stable node with low Sd/ES.

I would work in .4 to .6 increments, when you find something to explore, you can come back and shoot the .2 or .3 between the .4/.6. IE say you do .6 and like a node between 65.2-65.8 come back and shoot 65.5. Now you have data for the whole range.

target is not really needed, but can provide useful data, chronograph is required.

2) Once I find the powder/ bullet, I test for best primer. Again target not needed, chrono is.

3) do seating depth test. Preferably at 600 yards. But can be done closer.

The seating depth is to tune your load, or change the timing when it exits the barrel. Closer to the lands it exits faster, and pressure/speeds will be faster, farther from the lands, not only does it exit slower, but speeds will also decrease.

it serves no purpose to tune the load and then do your powder and change everything up. You'll end up chasing your tail.

Here's a picture of one of my seating tests. Lost 15 fps, but found a wide seating node that should stay tuned for the life of the barrel.

But…..your not done yet. Now to take it out to distance and verify the load.
Shoot in different weather, ect.

I just had a "great load" fall apart at 1,000 yards in 95 degree weather. Because I skipped the primer test.

Last night I did the primer test in 95 degree weather on 7SAUM/180hybrid.

26 rounds in 15 minutes over .5 grains of powder, combined SD 6.3 - ES 23 and that's with a barrel that was at 159 degrees at the end of the test.

hope this is helpful in someway.

For my experiences, your method makes sense to me.

I tried to do seating depth testing before powder testing (just because I hadn't tried it that way before) and it went terrible the one time I tried it. I won't be doing that again anytime soon.

Could you describe how you go about your primer testing or point to another thread that details it? I have recently found a few cartridges that saw significant improvement with primer changes, but I don't have a procedure that I follow specifically for primers.

 

[victor3ranger]

The 73g target shows some good potential.
I would work some loads starting at 72.7 and work my way up to 73.3 to see what happened

 

[BoomFlop]

I'm super confused on what you are trying to achieve with this test? You basically just loaded a pressure ladder in my mind. I would have done a seating depth test at 70 grains with a new rifle. Found a consistent poi as you are looking for in this test by adjusting seating depth. I then would have shot that powder ladder at 600 yards and looked for a 3-5 charges that shoot a good waterline while watching for pressure.

To me this test was basically a waste of components. You didn't find pressure, you did not test seating depth and basically do not know if powder charge is right but the seating depth is off.

Based on the target, I would agree that 73-73.5 does show some promise, but some of the other groups maybe a more consistent load that need seating tweaked.

I wish you the best bud, good luck!

Steve

 

[RegionRat]

There is way to much noise in terms of group centroid shift in the test.
There is either an issue with the bench technique, or the rifle doesn't like the recipe, or both.

Any variation on the OCW Method is aimed at a study of the group centroid. The goal is to see if there are at least a few charge steps where the centroid is stable and/or to at least avoid the steps where there is a rapid shift. On your test, you can hardly find any group centroid stability because the size of the groups and their variations are too large.

As often as not, in an OCW test we don't know anything about the group stats till after follow up tests of the best charge steps found in the first pass. Those follow up tests are the time to explore seating depth and to gather velocity stats and here is also where the user should consider distance testing.

Also, if we have set a goal that is reasonable, we have to learn when to punt or when to try harder on a recipe. That takes some skill, experience, and objectivity.

Small sample tests that study a chronograph are a problem in our sport. These chronograph dominated tests are very misleading when the context is a carry rifle and the sample sizes are too small.

When the context is a sporting carry gun, the challenge is the weight of the rifle and the recoil. Shooting a big cartridge in a light gun sets the stage for the potential accuracy, especially if the driver doesn't understand the discipline to control recoil reaction with extreme NPA and follow through. If the rig's reaction is allowed to vary, it is hopeless.

The Christensen Arms Mesa is called a featherlight in their adds and is roughly 6.5 lbs, which makes it very easy to carry up and down the mountains, but also makes it very difficult to shoot well. Set your distance and goals accordingly would be my advice.

That recoil, if left unmanaged by shooting technique, will dominate the target performance.

At the maximum range for a carry gun, the group study should take priority and the resulting velocity stats will follow. This metaphor will shift only slightly with a heavy barrel LR match gun or an ELR rig, but in fact the shot fall performance will only be good with excellent ammo workmanship and that is what determine those velocity stats in that context, and only after group testing selects the best recipe to begin with.

By definition, if the groups at distance are good, then so are the velocity stats. And, great velocity stats that sit on a scatter node are cold comfort. Don't fixate on velocity stats too early in the search or at short range. Those variations on what was called the Satterlee Method and so called "flat spots" evaporate when more samples are filled in.

The signal-to-noise challenge in load development is a real problem. Light rifles using heavy cartridges will emphasize the bench technique as the major contributor to shot dispersion. If the recoil isn't managed, your noise will be so large you can never see the secondary harmonics.