Standard Deviation issues

Dec 28, 2017
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#1
Hi everyone

I have been trying to find the right node for my Ruger Precision Rifle. Its a stock barrel in 6.5 creedmoor. I did initial testing to validate the right nodes and found 2 nodes to continue testing:

My setup:

6.5 Creedmoor RPR stock
Hornady Brass, fired around 3-5 times
Hodgon H4350
Federal Gold Match Primers
Hornady 140 grain ELDs

First test found 40.4 and 40.6 as the best nodes for 8 shot groups:

40.4:
2608
2617
2616
2617
2616
2628
2607
2615
SD: 6.43

40.6:

2625
2625
2636
2638
2619
2633
2628
2633
SD: 6.46

I then tested 40.4, 40.5, and 40.6 today with 20 shot groups and found:

40.4:
2624
2632
2622
2626
2635
2639
2636
2631
2637
2648
2637
2631
2637
2613
2611
2630
2632
2645
2635
2637
SD: 9.22

40.5:
2647
2636
2621
2640
2653
2633
2652
2646
2634
2638
2632
2626
2647
2650
2652
2644
2640
2640
2648
2650
SD: 9.04

40.6:
2657
2653
2649
2644
2643
2646
2656
2642
2638
2649
2643
2641
2630
2664
2661
2653
2645
2660
2644
2648
SD: 8.49

My SD clearly went up today. Additionally, my average speed went up across the board today for the 2 repeated loads (40.4 and 40.6). Things I changed: I used a brass tumbler today. I previously was rinsing with soap and water and shaking it in a bottle....which it is odd that my FPS standard deviation increased, as well as my FPS. Another thing that changed is a increased my case length about .001 inches, which seems somewhat small. I also found that 40.5 did not group as well as the others, but this might have just been my bad shooting at that node.

Thoughts, help? Trying to find the best node and wondering why my SD went up across the board.
 

Patruck825

Primer Poker
Mar 4, 2017
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#4
Id also suggest weight sorting the cases you use for mod testing and find cases that fall in the middle of the pack, Hornady case weights can be all over the place and cause a lot of deviation.
 

hookedonbrass

Sergeant of the Hide
May 16, 2018
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#5
my buddy has the same rifle, is using same bullets, hornady brass (1x fired though) and same powder as you, and his load he picked was 41.5g with a MV of 2701. just as a rough comparison. SD under 5 I believe.

not really what you are asking, but just bouncing off what Patrick above said.
 
Likes: LG65CM
Jul 29, 2014
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#6
you're a good 2-3 grains below where you could be. I dont even know that that's a middle node, probably a low one with two above it
 
Apr 18, 2014
872
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Colorado
#7
I'm going to be a bit contrary to the other recommendations here. Yes, you can increase your charge weight and explore a higher node, which you'll likely find in the 2800 fps neighborhood. If the low node is accurate, and you have no real need to have a faster load, such as competing where you'll really want to take advantage of the BC, there's nothing wrong with staying low. If you're using it in matches, then I would explore the higher node.

With that said, it's not like your SD jumped from 5 to 20. You're still in that acceptable range of SD (10 or lower). Your ES numbers are higher than I'd prefer, since they're all 25+ in your 20 shot groups.

Hornady brass is decent, but not spectacular. As someone else said, weight sorting your brass and even your bullets should help. Ideally, what you'd like to do is find components that all weigh as close to the same as possible, which would mean hopefully the same volume capacity for your brass. Consistency on the bench equals consistency at the firing line. If you really want to go down the rabbit hole, you can always leave the spent primers in and measure the H2O capacity for all your brass. You can also look into Alpha or Lapua brass, which are far more consistent than Hornady.

You might also want to tell us about your reloading procedures, specifically how you're setting your neck tension.
 
Apr 18, 2014
872
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Colorado
#9
@Patruck825 same for me when I switched to Alpha. Like I said in my post, Hornady was decent, but I'd always end up with one or two rounds that threw everything off. I would send 20 across my MagnetoSpeed and I'd see fifteen or sixteen that would give me a 12 to 15 spread and the others that were oddly off, like an extra 5 to 7 fps higher or lower, kinda like OP's list. His 20 shots at 40.4 are a perfect example. A majority of his rounds are in the 2635 to 2640 range, then there are four in the 2610 to 2620 range that you can't explain and just seem to throw the spread and SD off. Get rid of those four and the SD tightens up to 5.5
 
Likes: LG65CM
Dec 28, 2017
12
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#10
Thank you everyone for your input thus far. I’m pretty new to reloading. I’ve been trying to increase my precision after getting an Expert rating for a 600 yard NRA F-Class tournament. Used 38.6 for the tournament.

My setup is the 6.5 Ruger on an Atlas bipod, if this affects FPS.

Reloading order:
1. Deprime
2. Clean with stainless media
3. Lube
4. Full length resize RCBS normal die
5. Trim (rcbs case trimmer). I measure brass length
6. Prime
7. Powder (rcbs chargemaster)
8. Seat bullet. I measure overall length


To answer questions above:

*i just bought a salt bath annealer so I’ll be doing that soon.
*My first FPS test went to 41.6 (2691 avg FPS) which was 10.5 SD
*Havent weighed cases or bullets
*3 grains higher exceeds the book specs. Seems unsafe?
*i May have been testing improperly but have been paying attention more to getting bullets shot to check for FPS than for group sizing. I am specifically measuring to get a higher score for matches. I also am not paying attention to neck tension...don’t really know where I’d start or what that would affect.
*i bought a bunch of Hornady Brass on sale so I’d prefer to stick with it...plus Lapua primers are small. How big a difference in brass changes did you see and how does Lapua make things more consistent? Would weighing brass allow it to be consistent?

Thanks for the assistance
 
Jul 29, 2014
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#11
3 may be much but again depends on your rifle. the books are SUPER safe.

load up in .3-.5 grain increments and find the max load in YOUR gun (sticky bolt, flat primers, ejector swipe)

Lapua brass is just all around better. almost everyone will agree on that. you also have alpha, norma (prime), and peterson who would all be above hornady. but hornady will still work just fine look at their factory match offerings
 

Patruck825

Primer Poker
Mar 4, 2017
987
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#12
I have found neck tension to have a major impact on consistency. Too much and you can get erratic results. I like to have about .0015 tension in a bolt gun.
Measured a loaded round (with a micrometer, not a caliper) and see what it measures. Then measure a sized case, and see what the difference is.
 
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Culpeper

One divided by F
Nov 25, 2006
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#13
Like mentioned, The differences are immaterial. I would love to light up an M80 in the ass of those fools that came up with nodes and fucking harmonics. What a colossal waste of time and resources. Anbody bothered to ask if the OP is hitting anything.
 
Apr 18, 2014
872
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#14
Here are a couple of things that stand out to me:

If you're going to continue using Hornady brass and shooting F-class, I would weight sort both bullets and brass. I don't remember off the top of my head what a piece of Hornady brass weighs, but if your course of fire is 50 rounds for the the actual recorded fire and you have X for sighters, I'd find about 100 or so pieces of brass that all weigh as close to identical as posible. Same goes for the bullets. Find your "for record" bullets and set them aside, even if you have to crack open a couple of boxes until you find identical weight bullets. The next time you need to buy brass, I would HIGHLY suggest stepping up to Lapua or Alpha. Both have been extremely consistent in weight and case capacity.

I don't know what the RCBS shrinks the neck down to. For all I know, it might set neck tension at 0.004", but I would find out. I would then invest in a set of mandrels and a die. Here's the die I use. It's just a standard Sinclair mandrel die

https://www.brownells.com/reloading...ls/generation-ii-expander-dies-prod38807.aspx

And pick up one expander mandrel and one turning mandrel. If I remember correctly, the expander will set your neck tension at 0.001" and the turning mandrel at 0.002", but I might have those two confused.

https://www.brownells.com/reloading...inless-steel-expander-mandrels-prod33134.aspx

Since your RCBS die is setting your neck tension at X, the mandrels will accurately set your neck tension as described above. It's one more step at the bench and takes about 5 minutes. Just throw the mandrel die with your desired mandrel and run each case through to set your neck tension. Hornady brass doesn't have precise neck thickness around the entire diameter of the neck. Sizing with something like a bushing die, ensures the neck is perfectly round and at a certain diameter, but any imperfections in the neck thickness would be pushed inside. Using the mandrels not only sets your neck tension, but would also ensure the inside of the neck is perfectly round, forcing any of those imperfections to the outside and away from the bullet. Read up about neck tension and its effect on accuracy.

As far as the powder weight goes, only you and your rifle can determine how much is too much. You're already at 40.whatever you ended at. You can load up incrementally to find what YOUR max is. Be sure to look for pressure signs along the way at every step. If you don't know what to look for, here's a good read:

https://www.primalrights.com/library/articles/understanding-pressure

And, NO, I didn't ask the OP if he's hitting anything because that's not his question. I would assume he is, since he said he scored Expert at a recent F-class match, but even if he was hitting all Xs, his question had to do with lowering his SD.

Edit: I knew I forgot something! Buy yourself a comparator set and start measuring to the ogive of the bullet instead of just overall. You'll need to find the distance to the lands for your rifle, but it'll give you a more consistent seating depth.
 
Last edited:

Patruck825

Primer Poker
Mar 4, 2017
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#15
Like mentioned, The differences are immaterial. I would love to light up an M80 in the ass of those fools that came up with nodes and fucking harmonics. What a colossal waste of time and resources. Anbody bothered to ask if the OP is hitting anything.
Gotta disagree with you, conditions change, and with it, the characteristics of your chosen load. Being inside a node insures those changes have a minimal effect.
Though I agree, the differences in his SDs are inconsequential. Anything below 10 and the misses you see will more than likely be shooter related.
 
Likes: canezach
Apr 18, 2014
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#16
Gotta disagree with you, conditions change, and with it, the characteristics of your chosen load. Being inside a node insures those changes have a minimal effect.
Though I agree, the differences in his SDs are inconsequential. Anything below 10 and the misses you see will more than likely be shooter related.
Agreed! And especially about the part where you state the most likely cause for a miss would be shooter-related, but after reading OP's reloading practices, there are simple steps he can take that will improve his ammo, so why not offer some insight? (Not directed at you Patruck)
 

Patruck825

Primer Poker
Mar 4, 2017
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#17
Agreed! And especially about the part where you state the most likely cause for a miss would be shooter-related, but after reading OP's reloading practices, there are simple steps he can take that will improve his ammo, so why not offer some insight? (Not directed at you Patruck)
I think that’s what we’re all doing, but either way.

Personally, I would......

Switch to lapua brass (really the price is worth it)
Figure out your neck tension, findnout what it is. And if it isn’t .0015-.002 take steps to make sure that it is, like buying a bushing die that will properly size your neck.

Stop measuring OAL to seat bullets, they can vary, knowing where your lands are and how far you’re loading off of them consistently is crucial to accuracy and repeatability. Measure to the ogive of the Bullet for seating depth.

Anneal- 5 or so firings you’re going to start feeling the brass stiffen up, it’s most noticeable in Bullet seating.

Are you measuring how much you’re bumping your shoulders when you size? You should bump them .002

I didn’t see a step where you clean the sizing lube off your case, you may already but make sure you get your cases really clean, anything in your cases can cause all sorts of issues.
 
Dec 28, 2017
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#20
So I think the first thing I need to do is deal with seating depth. I got myself a OAL gauge from Hornady as well as a comparator. Now, the only issue i have is once i have measure the OAL for my bullets to ogive, how to i make sure that my base to ogive is consistent? Do I need to actually modify my seating die every time?

I've checked YouTube for instructions and all I've found are the reasons to measure base to ogive and not how to seat bullets to the right base to ogive length.

For example: If my base to ogive is 2.8 and I find that i've seated bullets at:

*2.98
*2.70
*2.8
*etc

Then I would need to unseat the 2.7 to get it longer and then seat the 2.98 to get it to 2.8.

Is there an easy way to do this without constantly varying the length of my seating die?
 

Culpeper

One divided by F
Nov 25, 2006
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#21
Trust the die setting on cartridges where the primer is flush or sunk into primer pocket. You shouldn't be resetting the die for each case. Otherwise, your bullets are not consistent in size.
 

spife7980

Full Member
Feb 10, 2017
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#22
If you have that much difference on the ogive you have some serious other issues. Usually I have maybe .001 of variance in either direction. Start a tad long and seat 5. Figure out what the group seems to be centered around and then adjust accordingly. Once I figure out where it needs to be I don’t bother adjusting the settings any further, let that .002 of variance be damned. But if you have .1 of variance... I’m not sure how that’s possible unless you’re using pliers and a hammer to seat them.

I you meant the over all length varies that much well... yeah. That’s why the hornady headspace comparators are so helpful. The ogive is consistent, overall lengths can be wildly un so.
 
Aug 7, 2014
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#23
Trust the die setting on cartridges where the primer is flush or sunk into primer pocket. You shouldn't be resetting the die for each case. Otherwise, your bullets are not consistent in size.
What did you really say here? Shellholders have a hole in the center for primers or priming, even Lee ones that don't have a slot would allow for proud primers.
 

Patruck825

Primer Poker
Mar 4, 2017
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#26
I have seen variances in seating depth like that when neck tension is way too much. Check a sized case and compare it to a loaded case like I said above. There should only be .0015-.002 difference
 
Dec 28, 2017
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#27
i didnt mean i actually was getting those measurements - just an example because i need to know what to do if ive loaded short

I want to gather information on what to do while i wait for an order of a comparator and new caliper.
 

Patruck825

Primer Poker
Mar 4, 2017
987
101
28
Northern VA
#28
i didnt mean i actually was getting those measurements - just an example because i need to know what to do if ive loaded short

I want to gather information on what to do while i wait for an order of a comparator and new caliper.
You won’t vary that much unless you have royally messed something up. I seat my bullets and allow .001 in either direction of my target depth.
 
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