Load Development - Next Steps

[ABL_ZA]

Can anyone help me with best next steps for my load development?

Disclaimer:

• I am a newbie, please help with my terminology if not correct.
• I am new to reloading

Context:

I have a new rile - Tikka T3x 6.5CM

Only 60 rounds of 143gr ELDX through it.

Case Prep

• Lapua Brass (virgin)
• 1.910 case length
• Mandrel .262
• Deburred

OCW Test
I was using CCI 450 primers and H4350
OAL 2.855 (JAM was at 2.954 so I had to reduce it to max mag length)
100m range

Grains	Shot 1	Shot 2	Shot 3	Shot 4	Shot 5	Average	Group	ES	SD
41.4	2635	2640	2635	2644	2633	2637	.777 MOA	11	4.3
41.6	2635	2647	2627	2670	2653	2646	1.034 MOA	43	15.34
41.8	Error	2648	2663	2675	2660	2661	.537 MOA	27	9.6
42	2699	2693	2682	2670	2673	2683	1.034 MOA	29	8.96

Additional comments
I want to shoot in the NRL hunter so I need a velocity of 2658+ for 143 ELDX (to reach 380,000 power factor).

 

[spife7980]

Now shoot it on paper and see what it’s actually doing.

 

[KnowNothing256]

An OCW test looks at impact location trends, not MV trends. Also, you might consider pushing the load faster, depending on whether or not you are seeing pressure signs. 25 FPS isn’t a lot of margin to make power factor.

 

[ABL_ZA]

An OCW test looks at impact location trends, not MV trends. Also, you might consider pushing the load faster, depending on whether or not you are seeing pressure signs. 25 FPS isn’t a lot of margin to make power factor.

I did a pure ladder test last week (with magnetospeed issues) and then chose to do a combined OCW test today by shooting 5 shots measuring both impact and velocity for all of them. 5 shots at 41.4, 5 shots at 41.6 etc.

The problem is I did not get a great or obvious SD / impact combo that I want to pursue.

Thinking the best next move is to look at 41.4 and seat deeper to get increased velocity and possibly better accuracy. Thoughts?

 

[spife7980]

Seating deeper won’t increase your velocity.

 

[KnowNothing256]

Did you use the MS for your OCW impact test? If so, I recommend taking it off, it'll affect POI somewhat unpredictably (but usually the bullet will deflect away from the bayo). You also appear to have mixed up the ES and SD numbers; ES will always be larger than SD. Also, on your 41.8gr test, assuming we toss the Shot 1 error, you have an SD of 6.5 and an ES of 15, which looks pretty darn good, although it's too slow for your needs.

Here's the chart:

Honestly I think you should see if you can keep bumping up charge weight unless you're seeing pressure signs, but you need to run the OCW test without the MS on the gun, then come back and check MV of your pet load.

 

[nn8734]

I did a pure ladder test last week (with magnetospeed issues) and then chose to do a combined OCW test today by shooting 5 shots measuring both impact and velocity for all of them. 5 shots at 41.4, 5 shots at 41.6 etc.

The problem is I did not get a great or obvious SD / impact combo that I want to pursue.

Thinking the best next move is to look at 41.4 and seat deeper to get increased velocity and possibly better accuracy. Thoughts?

Post pics of the target. Don’t worry about SD at this point in the process.

 

[ABL_ZA]

Did you use the MS for your OCW impact test? If so, I recommend taking it off, it'll affect POI somewhat unpredictably (but usually the bullet will deflect away from the bayo). You also appear to have mixed up the ES and SD numbers; ES will always be larger than SD. Also, on your 41.8gr test, assuming we toss the Shot 1 error, you have an SD of 6.5 and an ES of 15, which looks pretty darn good, although it's too slow for your needs.

Here's the chart: View attachment 7896987

Honestly I think you should see if you can keep bumping up charge weight unless you're seeing pressure signs, but you need to run the OCW test without the MS on the gun, then come back and check MV of your pet load.

Sorry SD was wrong. I have now used the STDEV.P() function in excel which gives me 9.6 for 41.8gr. I also used max less min for ES. Is this wrong?

I use a Zero Runout mount for my MS so it's not on the barrel. *Not my pic or rifle below, this is just showing you what I use.

 

[ABL_ZA]

Post pics of the target. Don’t worry about SD at this point in the process.

*Scope not yet zero'd

 

[savagemann]

Hopefully once you've gotten another 150 or so rounds through it it'll speed up a little bit.

 

[KnowNothing256]

STDEV.S is technically more appropriate, but it’s not a huge deal. Your formula for ES is correct.

I’ve seen mixed results with the off-barrel MS mounts; I had the Wiser mount, used it just long enough to verify that I still had a POI shift so I sold it on down the road. Cool concept, just didn’t work for me. So my takeaway was that the MS can still impact POI, so I don’t ever use it if I’m shooting for groups. Others feel differently, but it’s very easy to test; shoot a group with it on your mount, then take the whole assembly off and shoot without. If your POI is the same, you *might* not be influencing the bullet, but since group size is about more than just average POI, I’m still not personally willing to risk contaminating my results.

Bottom line, my advice is to re-run your OCW with no MS involved, plot your average POI location for each group, then look for 2-3 consecutive groups with the same average POI. Group size is then tuned using seating depth, one you pick your preferred charge weight. I think you also need more powder to make your desired power factor, but proceed carefully and at your own risk. Tikka barrels have a reputation for being slow, so you might just be limited to running right at the edge, or you might switch to the 147 ELDM which will let you drop to a minimum 2600 MV.

 

[ABL_ZA]

STDEV.S is technically more appropriate, but it’s not a huge deal. Your formula for ES is correct.

I’ve seen mixed results with the off-barrel MS mounts; I had the Wiser mount, used it just long enough to verify that I still had a POI shift so I sold it on down the road. Cool concept, just didn’t work for me. So my takeaway was that the MS can still impact POI, so I don’t ever use it if I’m shooting for groups. Others feel differently, but it’s very easy to test; shoot a group with it on your mount, then take the whole assembly off and shoot without. If your POI is the same, you *might* not be influencing the bullet, but since group size is about more than just average POI, I’m still not personally willing to risk contaminating my results.

Bottom line, my advice is to re-run your OCW with no MS involved, plot your average POI location for each group, then look for 2-3 consecutive groups with the same average POI. Group size is then tuned using seating depth, one you pick your preferred charge weight. I think you also need more powder to make your desired power factor, but proceed carefully and at your own risk. Tikka barrels have a reputation for being slow, so you might just be limited to running right at the edge, or you might switch to the 147 ELDM which will let you drop to a minimum 2600 MV.

Would it be ok to run 3 shot groups in 1 grain increments?

41.4 | 41.5 | 41.6 | 41.7 | 41.8 | 41.9 | 42

I am not brave enough to go beyond 42.0. I am not confident in identifying pressure signs. I will post the cases and maybe someone can confirm.

 

[Patty]

41.4 and then do a seating depth test with it, its almost there

 

[AllenOne1]

To consistently get your required velocity you are going to need to go beyond 42 gr of powder. Increase powder by .2 gr (42, 42.2, 42.4, 42.6) Look for pressure signs after each powder weight change to see if you can keep going. Look for a velocity in the 2720-2730 range.

After you get the required velocity move to a seating depth test to tighten up the groups. Start at mag depth were you are and seat the bullet an additional .003 for each test depth. 10 rounds of 3 shots should be enough to tell you where you are going.

Then buy an EC Tuner so you can continue to drive yourself crazy.

Best of luck,

 

[KnowNothing256]

Would it be ok to run 3 shot groups in 1 grain increments?

41.4 | 41.5 | 41.6 | 41.7 | 41.8 | 41.9 | 42

I am not brave enough to go beyond 42.0. I am not confident in identifying pressure signs. I will post the cases and maybe someone can confirm.

3-shot groups are fine, and I think 0.2gr increments would be better.

If you aren’t ready to go beyond 42gr, you probably need to run the 147gr ELDM, or get factory ammo. Stiff bolt lift is usually the first pressure sign I notice; primer cratering is next, and primer punctures is way too far. Web bulging is another indicator, but I’ll be honest, I never look for it.

 

[Doom]

Looking at the 6.5CM you need to get to a 147 gr bullet to have any room for error AND stay within SAAMI pressure limits. With the 143 you will have to venture into the above max load area.