repeatability issues

[westtx]

Good morning guys, advice needed, long post.

Having trouble with repeatability in load development. I won’t get to every detail but ran through a test in a Tikka 7mm-08 using varget//win WLR primers//starline brass//140 nosler ballistic tips. Started 3 round groups in 0.5 grain increments and identified a node to dive into. All groups were sub MOA with decent speed and some ES numbers that I could work with. I then loaded up 5 shot groups in 0.3 grain increments and landed on two loadings with 15-16 ES and about 10 SD. Couldn’t be going any better at this point.

Here’s where I’m needing some help. I haven’t been able to repeat since. I’ve loaded up two separate 10 shot groups in the “sweet” spot and seeing velocity numbers through the roof, as in 30-60 ES. The accuracy is still there (0.5 to 0.7 moa) but frustrated with the spreads.

The load isn’t intended to be anything over 500yards, and I’ve run some ballistics test to show the ES doesn’t make more than an inch or two difference at that distance, but would like to tighten the velocity up.

Brass was new when I started (trimmed all to same length and chamfered), and ran through about 75 rounds of the star line before switching to Lapua. Lapua actually made it worse (for this test). Scale is the same and calibrated (hornady auto-loader), seating depths are all the same (redding type s set), primers seated as best I can (hornady hand primer) . All rounds were opened up with a expander mandrel to begin and tension should be 0.002.

Any help from you guys? Sorry for the long post.

 

[Supersubes]

Confused on your brass switch. You worked up the load with starline, then switched brass, and now the Es is shit?

 

[westtx]

Confused on your brass switch. You worked up the load with starline, then switched brass, and now the Es is shit?

No I couldn't repeat with the starline, so switched to lapua to see if there were any improvements. To clarify, the original load was worked with Starline and had 15-16 ES with 41.3 to 41.6 grains. Loaded 10 of each at 41.3 to 41.6 and ES jumped to 30-40 ft/s. Tried that a few more times with similar results so that's when I decided to switch and start over with Lapua. Tested the same 0.5 grain increments as I did with the Starline and didn't get any ES worth continuing LD with (40-60ft/s when compared to same loads with starline).

 

[Dthomas3523]

30-40 ES is probably the best you’re gonna get with that scale. That’s also about the best most people will get in the long run regardless.

 

[westtx]

30-40 ES is probably the best you’re gonna get with that scale. That’s also about the best most people will get in the long run regardless.

Good point, I've been thinking scale could be a main contributor. Considering an upgrade. Currently watching @elfster1234 video comparing a Chargemaster to the A&D.

 

[Supersubes]

What’s the state of the brass for these see tests, virgin, fired etc? If both, was a difference noted between them? How much are you jumping bullets?

 

[westtx]

What’s the state of the brass for these see tests, virgin, fired etc? If both, was a difference noted between them? How much are you jumping bullets?

Virgin brass. Loaded to max mag length (2.235" CBTO). Don't have my notes at the moment but its jumping somewhere in the range of 0.150". I could size and test again. Initial measurements of the virgin brass were within 0.001" shoulder, neck/body junction/web. I haven't measured the fired brass yet which might show where some inconsistencies are coming from?

 

[Steel head]

30-40 ES is probably the best you’re gonna get with that scale. That’s also about the best most people will get in the long run regardless.

Actually if your in a good speed node the Hornandy auto throw easily can do better than the OP’s results.
I never had an issue getting 6-8 SD in 10 shots or more.

 

[Gustav7]

No I couldn't repeat with the starline, so switched to lapua to see if there were any improvements. To clarify, the original load was worked with Starline and had 15-16 ES with 41.3 to 41.6 grains. Loaded 10 of each at 41.3 to 41.6 and ES jumped to 30-40 ft/s. Tried that a few more times with similar results so that's when I decided to switch and start over with Lapua. Tested the same 0.5 grain increments as I did with the Starline and didn't get any ES worth continuing LD with (40-60ft/s when compared to same loads with starline).

Are you saying you noticed a node from 41.3-41.6? IF thats the case, then you don't want to load on the edges of that, you want to load in the middle. So either 41.4 or 41.5.

Are you verifying neck tension?

Also, did you do the same sample size? Meaning did you take ES measurements off 3 shots, then followed up with 10? Cause thats definitely going to change your ES up.

I usually get ES's in the 15-20fps area for 5-10 shots, and between 20-30fps for 10+
I use Starline SRP brass and two Chargemasters

 

[Dthomas3523]

Actually if your in a good speed node the Hornandy auto throw easily can do better than the OP’s results.
I never had an issue getting 6-8 SD in 10 shots or more.

Everything can produce good sd. He said his ES is up.

That’s where scale quality over the long term comes in. Your ES can be wrecked with one or two charges. Your SD doesn’t get wrecked like that. Which is why you can have a low sd and a high es.

 

[Newbie2020]

Everything can produce good sd. He said his ES is up.

That’s where scale quality over the long term comes in. Your ES can be wrecked with one or two charges. Your SD doesn’t get wrecked like that. Which is why you can have a low sd and a high es.

Standard Deviation Formulas

www.mathsisfun.com

Holy crap. Math and stuff.... haha

 

[westtx]

Are you saying you noticed a node from 41.3-41.6? IF thats the case, then you don't want to load on the edges of that, you want to load in the middle. So either 41.4 or 41.5.

Are you verifying neck tension?

Also, did you do the same sample size? Meaning did you take ES measurements off 3 shots, then followed up with 10? Cause thats definitely going to change your ES up.

I usually get ES's in the 15-20fps area for 5-10 shots, and between 20-30fps for 10+
I use Starline SRP brass and two Chargemasters

Initial 3 shot groups in 0.5 grain increments showed 41.0-41.5 to be a good spot with 41 having ES @ 15, 41.5 having ES @ 16. So split it and went 5 shots @ 41.3 & 5 @ 41.6. For the 5 shots at 41.3 my chrono missed the 1st, and then the 5th was a slow round that sent ES to 30 with an SD of 14. For the 5 shots @ 41.6 I ended with a 0.65 group with ES of 9/SD of 3.6 which I thought was outstanding. So I then loaded up 10 rounds at 41.6 and ended with a 52 ES/17SD which also includes a slower round. Removing the slow round, that same 9 shot group yields a 28 ES/11SD. The more I think about it I could live with a 28ES/11SD if I can get it to repeat. Also more I look it I need to figure out why I'm getting a random slow round.

 

[Gustav7]

Initial 3 shot groups in 0.5 grain increments showed 41.0-41.5 to be a good spot with 41 having ES @ 15, 41.5 having ES @ 16. So split it and went 5 shots @ 41.3 & 5 @ 41.6. For the 5 shots at 41.3 my chrono missed the 1st, and then the 5th was a slow round that sent ES to 30 with an SD of 14. For the 5 shots @ 41.6 I ended with a 0.65 group with ES of 9/SD of 3.6 which I thought was outstanding. So I then loaded up 10 rounds at 41.6 and ended with a 52 ES/17SD which also includes a slower round. Removing the slow round, that same 9 shot group yields a 28 ES/11SD. The more I think about it I could live with a 28ES/11SD if I can get it to repeat. Also more I look it I need to figure out why I'm getting a random slow round.

1.) You could actually be on the edge of a node and since your Powder Dropper isn't super consistent, its giving you some velocities in the node and some out.
2.) You're using a cheap chronograph and its giving you oddball velocities
3.) Neck tension could be weird with the new cases. When I first did my Starline cases most only required my turning mandrel to get straightened out and give me 2 thou neck tension, but some were a little larger and were closer to 1, but the mandrel wasn't touching them. Switched to my expander mandrel and it cleaned it up. Make sure your mandrel is getting all the way down the neck of the brass with the actual shaft of the mandrel too.
4.) You could try different primers.... The cowboy shooting field loves those Winchester primers...but you don't hear much about them in the precision world.

If its 52 ES and only 1-2 rounds is making it that much by 25-30fps, then I'd look to your reloading process (including powder).

 

[westtx]

1.) You could actually be on the edge of a node and since your Powder Dropper isn't super consistent, its giving you some velocities in the node and some out.
2.) You're using a cheap chronograph and its giving you oddball velocities
3.) Neck tension could be weird with the new cases. When I first did my Starline cases most only required my turning mandrel to get straightened out and give me 2 thou neck tension, but some were a little larger and were closer to 1, but the mandrel wasn't touching them. Switched to my expander mandrel and it cleaned it up. Make sure your mandrel is getting all the way down the neck of the brass with the actual shaft of the mandrel too.
4.) You could try different primers.... The cowboy shooting field loves those Winchester primers...but you don't hear much about them in the precision world.

If its 52 ES and only 1-2 rounds is making it that much by 25-30fps, then I'd look to your reloading process (including powder).

I broke down after a few juice box's and ordered a Labradar and an A&D FX12i. Expensive endeavor, I know, but should be able verify charge weights and velocity readings are correct and then keep or sell depending on the results.

For the Starline prep I didn't have an expander mandrel yet so I ran the expander ball that comes with the Redding FLS. It was backed out enough that no sizing took place, just opening up the mouths and ironing out the dents (midway sure doesn't package bulk brass very well). My expander die and mandrel showed up with the Lapua brass, so it got the expander mandrel. Do you think using the expander ball on the Starline brass was a bad move?

My loads came from the Nosler manual, and they used WLR so that's the direction I started. I do have some CCI #200's and I think Fed 210's?