Load Development Interpretation

[jstanton]

I got some confusing results this weekend for a new load I am working up and was hoping someone could give me insight on what may be going on. Here are the details about the gun and components.

Alamo Precision Custom 6.5 Creedmoor
24" Bartlein Barrel w/ 1:8 Twist
New Lapua SRP Brass
CCI 450 Primers
H4350 Powder
Berger VLD Hunting 140gr.
Seating Depth .025" Off Lands
Neck Tension .002" (.262")

After the first round of load development on 4/9/2022 I thought I had it pretty well zeroed in using 40.7 grains of H4350. The 5 shot group size was 0.41 MOA, average velocity was 2662, SD 4.4, and ES of 11. I felt pretty good about these results but decided I would load up another 5 rounds with this same configuration to verify and some additional rounds increasing in 0.3 grain increments to see if there was another node at a higher velocity since I did not have any signs of pressure. So I went back to the range this weekend on 5/7/2022 and the same 40.7 grain load yielded a 0.95 MOA group, average velocity of 2654, SD 8.6, and an ES of 22.

To confuse matters even more, at least for me, was with 41.1 grains I shot a 0.9 MOA group, average velocity of 2687, SD 4.2, and an ES of 11. Not counting the group size, this was the best data of any combination that day. I know I can probably play with the seating depth and tighten this one up. The prior outing on 4/9/2022 using 41.2 grains was one of the worst groups. The best group size I achieved was with 41.5 grains which I shot a 0.39 MOA group, average velocity of 2713, SD 6.7, and an ES of 17. These are still very good results and I did not have any signs of pressure. Oddly enough the 41.3 grain group was the worst of the day.

Temperature wise between the two outings was only about a 3-4 degree difference. I throw all my charges with an RCBS powder dispenser and weight each one on a beam scale. I also measure every round with a set of Mitutoyo calipers and Hornady comparator for seating depth. The only thing I do to the new brass is chamfer the inside and outside of the case mouth and set neck tension.

Here are pictures of the two targets and PDF with all of the data compiled from the Magneto Speed.

Hoping someone might have some insight into what is going on here.

Thanks,
Jacob

 

[Taylorbok]

is your magneto speed attached to your barrel or are you using some sort of mount?
I wouldn't be shooting for accuracy with that strapped to the barrel.

 

[Jud96]

I agree with @Taylorbok. If you're using a Magnetospeed it should only be used for velocity and not POI or groups. Having said that, to me it looks like 40.7-41.3 is a node if just looking at velocity. However, I like to map point of impact shift for varying charge weights like an OCW test. In my experience, if I find a window where the groups impact at the same or very similar point of impact for 2-3+ loads across 0.4-0.6+ grains of powder and they're also close in velocity, that's a nice node in my book. I wouldn't worry about groups size if you're just testing powder charges. The rifle is showing you it has potential with a couple groups near 1/2 MOA and one better. You can tune your group size by adjusting seating depth.

 

[26Reload]

You actually answered your own question in the list......NEW Lapua brass....brass sizing to chamber when fired...reloaded isn't gonna 'stretch' to fill the void.....

 

[jstanton]

is your magneto speed attached to your barrel or are you using some sort of mount?
I wouldn't be shooting for accuracy with that strapped to the barrel.

Yes it is strapped to the barrel. I am not necessarily shooting for accuracy with it attached though. In my experience with it, I only see a point of impact change with little affect on group size at 100 yards.

 

[jstanton]

You actually answered your own question in the list......NEW Lapua brass....brass sizing to chamber when fired...reloaded isn't new to 'stretch' to fill the void...

It was new brass both times.

 

[sndmn11]

I have the same cartridge and bullet at 2835 from a 20" barrel with great accuracy behind staball.

I'd think there's a lot left in there and probably a higher node that would give you what you are seeking.

 

[jstanton]

I agree with @Taylorbok. If you're using a Magnetospeed it should only be used for velocity and not POI or groups. Having said that, to me it looks like 40.7-41.3 is a node if just looking at velocity. However, I like to map point of impact shift for varying charge weights like an OCW test. In my experience, if I find a window where the groups impact at the same or very similar point of impact for 2-3+ loads across 0.4-0.6+ grains of powder and they're also close in velocity, that's a nice node in my book. I wouldn't worry about groups size if you're just testing powder charges. The rifle is showing you it has potential with a couple groups near 1/2 MOA and one better. You can tune your group size by adjusting seating depth.

What would attribute the significant change in SD and ES to for the 40.7 grain load? It essentially doubled between the two outings. While the velocity of the 41.3 grain group aligns with the 40.7-41.1 loads, the ES is quite a bit larger so I would probably throw that one out. Wouldn't similar points of impacts just be a function of similar velocity with everything else being equal? I always thought you mapped point of impact to identify a node when you don't shoot across a chronograph. Also, given the data so far, where would you go from here to fine tune this load?

Thanks in advance!

 

[jstanton]

I have the same cartridge and bullet at 2835 from a 20" barrel with great accuracy behind staball.

I'd think there's a lot left in there and probably a higher node that would give you what you are seeking.

Wow! That sounds extremely fast for a 6.5 Creedmoor out of a 20" barrel. Going off the Berger book it shows 40.7 to be max load @ 2634 and 96% fill ratio. Since I didn't have any pressure signs the first time out at 41.2 I crept it up to 41.5 and still no pressure signs. Most guys I've seen running this combo are getting best results in the 2650-2750 range.

 

[Jud96]

What would attribute the significant change in SD and ES to for the 40.7 grain load? It essentially doubled between the two outings. While the velocity of the 41.3 grain group aligns with the 40.7-41.1 loads, the ES is quite a bit larger so I would probably throw that one out. Wouldn't similar points of impacts just be a function of similar velocity with everything else being equal? I always thought you mapped point of impact to identify a node when you don't shoot across a chronograph. Also, given the data so far, where would you go from here to fine tune this load?

Thanks in advance!

The more you test the same load, the more the ES will grow. Also, things like environmental changes, the accuracy of your reloading equipment, consistency of brass, etc all affect shot strings day in and day out. I focus on getting ES consistently under 25 FPS, even if it's consistently under 30 FPS for 5-10 shot strings that's good. Everyone wants ES in the teens or lower, but in reality if you have a node that's 0.5gr wide or more and your ES is consistently under 30, and the accuracy is 1/2 MOA, that's a serious long range load. You shouldn't have a problem making impacts out to 1000 yards with that level of load. It's rare to have a load repeat the same ES over and over. You're just seeing the broad spectrum of the loads performance on different occasions.

Similar points of impact are more due to barrel harmonics and not necessarily similar velocities. If you would shoot say 40.0-42.0 in 0.2-0.3gr increments for 3 shot groups from left to right on a row of targets, you could watch the groups raise and lower and then you'll see a flat spot and then the next group will shift the point of impact. I do this test, coupled with a velocity test with the same charges. When the flat spot in velocity aligns with a flat spot on paper, you have a winner. It's not always going to be miraculous with 3 loads having single digit ES and points of impact varying no more than 1/4". Most of the time you'll have a window where the ES between the multiple loads will be like 20-30fps and the points of impact are within 0.5-0.6". That doesn't sound beautiful, but the loads on either side of this window could have impact shifts as much as 1" difference. You're just looking to find the node and stick in the center of it. Then do a seating depth test to shrink your groups to the best you can get.

 

[jstanton]

The more you test the same load, the more the ES will grow. Also, things like environmental changes, the accuracy of your reloading equipment, consistency of brass, etc all affect shot strings day in and day out. I focus on getting ES consistently under 25 FPS, even if it's consistently under 30 FPS for 5-10 shot strings that's good. Everyone wants ES in the teens or lower, but in reality if you have a node that's 0.5gr wide or more and your ES is consistently under 30, and the accuracy is 1/2 MOA, that's a serious long range load. You shouldn't have a problem making impacts out to 1000 yards with that level of load. It's rare to have a load repeat the same ES over and over. You're just seeing the broad spectrum of the loads performance on different occasions.

Similar points of impact are more due to barrel harmonics and not necessarily similar velocities. If you would shoot say 40.0-42.0 in 0.2-0.3gr increments for 3 shot groups from left to right on a row of targets, you could watch the groups raise and lower and then you'll see a flat spot and then the next group will shift the point of impact. I do this test, coupled with a velocity test with the same charges. When the flat spot in velocity aligns with a flat spot on paper, you have a winner. It's not always going to be miraculous with 3 loads having single digit ES and points of impact varying no more than 1/4". Most of the time you'll have a window where the ES between the multiple loads will be like 20-30fps and the points of impact are within 0.5-0.6". That doesn't sound beautiful, but the loads on either side of this window could have impact shifts as much as 1" difference. You're just looking to find the node and stick in the center of it. Then do a seating depth test to shrink your groups to the best you can get.

That all makes sense, thank you! Your right I had it in my mind that my ES and SD should always be similar every time all things being equal. If my SD is in the single digits and ES in the mid to low teens, then I want it to be close to that every time but I understand what your saying and just need to have a better understanding of what an acceptable spread is for ES and SD on the same load.

Looking back over the results again I cannot get away from that 41.2 and 41.3 group. It just seems a lot worse than the 40.7-41.1 groups. I also can't explain the higher velocity of the 41.2. It makes me want to just through them out of the equation and focus on the 40.7-41.1. The outlier is that 41.5 group that looks good too. What do you think?

Would you say just pick 40.9 and start adjusting seating depth for accuracy?

 

[Jud96]

That all makes sense, thank you! Your right I had it in my mind that my ES and SD should always be similar every time all things being equal. If my SD is in the single digits and ES in the mid to low teens, then I want it to be close to that every time but I understand what your saying and just need to have a better understanding of what an acceptable spread is for ES and SD on the same load.

Looking back over the results again I cannot get away from that 41.2 and 41.3 group. It just seems a lot worse than the 40.7-41.1 groups. I also can't explain the higher velocity of the 41.2. It makes me want to just through them out of the equation and focus on the 40.7-41.1. The outlier is that 41.5 group that looks good too. What do you think?

Would you say just pick 40.9 and start adjusting seating depth for accuracy?

To me 40.9 looks to be a good place to be. I would definitely do seating depth testing there. Also, the 41.5gr load might be the start of another node. You can further test 41.5-42.5 and see if there's anything in there that's promising. Just keep an eye out for pressure signs as you work up.

I like to start .010 off the lands and work back in .005 increments. I typically will test .010-.050 off. I look for 2-3 loads in a row with good groups and load to the shortest of the 2/3 and call that good. I shoot 2 shot groups and again look for a window where I'm getting the bullets touching or dang close for 2-3 depths and with similar points of impact. You'll have some ugly ones but that's the point of the test. You can do 3-5 shot groups to get a better idea, but I like to conserve components and 2 shots gives me a good idea. I'll then go back and test 3-5 shot groups to confirm the precision of the load.

Below is an example of a seating depth test I shot. The orange target is me verifying the load and the zero. There's 5 shots in the top group and then 3 in the center. These were seated .010 off the lands which was the start of my seating depth node as you can see.

 

[sndmn11]

Wow! That sounds extremely fast for a 6.5 Creedmoor out of a 20" barrel. Going off the Berger book it shows 40.7 to be max load @ 2634 and 96% fill ratio. Since I didn't have any pressure signs the first time out at 41.2 I crept it up to 41.5 and still no pressure signs. Most guys I've seen running this combo are getting best results in the 2650-2750 range.

Seems like you missed the point of my comment.

 

[waveslayer]

I think you're looking at the OCW test the wrong way , it's not for groups it's for nodes and then for groups.

Like another intelligent person commented on here, shoot enough and that little ES will grow and grow and change etc.

You are on the low end using 40.9 area. There's a node at 40.5- 40.9. You are starting to see another node with the upper charges . I run my Creedmoor on the upper end with 43.2 grains , but that's for my barrel... so you're on the right path just looking at it the wrong way. Look for node patterns not tight groups, those tight groups are most often never repeatable