Help with huge standard deviation in handloads.

355sigfan

355sigfan

Sergeant
Full Member
Minuteman
Apr 12, 2004
328
5
Alaska
#1
Tell me how the same load in one rifle has a standard deviation of 9 and in another its huge

Noveske target
Noveskewith77grainNolserN135225grains.jpg

Larue target.
LarueN135Maxload77grainNosler.jpg


The shot that is low right on the lower right hand target had a different report almost like a hang fire but not that delayed. I am using new Lake City Brass. I have noticed that my Larue will some times push bullets in the case if I don't use a bit of crimp while my Noveske with M4 feed ramps does not have this issue. I used a small amount of crimp on these bullets. I was thinking that the feeding cycle in the larue could be causing some of my problems. Not really sure what is going on here.
Pat
 
#2
Re: Help with huge standard deviation in handloads.

Don't know how to explain this big deviation, but judging from the groups the gun doesn't care. In fact, other than the 1 flier, the massive deviation gun did better than the other one. I'm absolutely no expert, but I've found the more info I have sometimes distracts me from the main goal of my quest for a better load. In other words, if I didn't have access to a chrono I'd never know the deviation was different from 1 gun to the next and I'd be pretty happy with the results on the Larue. We amass more and more tools to help us figure this stuff out, but sometimes those tools get in the way.

Did you deburr the flash holes inside the case? I have found that LC brass is my worst offender about leaving massive curls of brass around the flash hole and just the other day found 1 hole half obscured by brass. This was on new LC brass from Natchez Shooter's Supply. Other than a low powder charge or something, this would be my best guess on the squib load.
 
#3
Re: Help with huge standard deviation in handloads.

Until the brass is fire formed for the chamber don't worry about SD/ES, took much energy is being used to expand the brass, after the first firing and resizing can the true SD/ES be examined.
 
#4
Re: Help with huge standard deviation in handloads.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 427Cobra</div><div class="ubbcode-body">Until the brass is fire formed for the chamber don't worry about SD/ES, took much energy is being used to expand the brass, after the first firing and resizing can the true SD/ES be examined. </div></div>

+1 to this. Also, what are you using to throw the powder? What chronograph are you using?
 
#6
Re: Help with huge standard deviation in handloads.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mtrmn</div><div class="ubbcode-body">Don't know how to explain this big deviation, but judging from the groups the gun doesn't care. In fact, other than the 1 flier, the massive deviation gun did better than the other one. I'm absolutely no expert, but I've found the more info I have sometimes distracts me from the main goal of my quest for a better load. In other words, if I didn't have access to a chrono I'd never know the deviation was different from 1 gun to the next and I'd be pretty happy with the results on the Larue. We amass more and more tools to help us figure this stuff out, but sometimes those tools get in the way.

Did you deburr the flash holes inside the case? I have found that LC brass is my worst offender about leaving massive curls of brass around the flash hole and just the other day found 1 hole half obscured by brass. This was on new LC brass from Natchez Shooter's Supply. Other than a low powder charge or something, this would be my best guess on the squib load. </div></div>

I agree with this, I assume you are shooting a .223, and in two diffwerent AR's? And judging by the way the second target looks it doesn't matter, it groups better. It is rather bizzare though.
 
#8
Re: Help with huge standard deviation in handloads.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Alaskapopo</div><div class="ubbcode-body">I am reloading on a Dillon 550B. I did not do any brass prep on the new brass.
pat </div></div>

In that case, I recommend getting a flash hole deburring tool and setting aside a small experimental lot of the new brass for testing after removing the burrs inside the case. I believe you'll be suprised how much brass falls out. In my limited mind, I can see the uneven powder ignition these burrs may cause. I use a Lyman tool. Various companies make them. In my case I did notice a small difference in group size but my cheapass chrono will only work in full sunlight so I don't have any before/after results on SD.
 
#9
Re: Help with huge standard deviation in handloads.

You have 2 $2000+ rifles and have the ability to handload for them, but did not do any brass prep while using new LC brass.
grin.gif
The brass prep may be unneccessary to some, but it sure makes <span style="font-weight: bold">me</span> feel good.

As others pointed out earlier, I also won't get overly bothered by the numbers on brand new brass. Since you are working up a load and paying attention to the numbers, do some brass prep and weigh those charges. I know a lot of sources say you must crimp with an AR, but my Forster FL dies give me enough neck tension that I just don't do it, but that's just me. I load in AR's for .223 and 6.5 Grendel BTW. You sound like you have nice equipment so give it the respect it deserves and I bet it will reward you. If it doesn't after all the work, you can always treat it like crap later!

I don't know for a fact that flash hole burrs cause higher deviations because I always deburr my cases. It can't hurt the brass as long as you don't ty to drill on through.

I have personnaly found loading for AR's is tougher than loading for a bolt gun. This is assuming you are trying to load for accuracy and not blasting ammo.

Don't take this as me being critical of what your reloading prctices, because I was not.

My $.02 and all that.......
 
#11
Re: Help with huge standard deviation in handloads.

Your groups are representative of semi-automatic rifles shooting unimproved brass.

For minimal Standard Deviation and Extreme Spread you're going to need to tune all cases for uniformity (like benchresters do). As recommended (even though new) you're going to need to tune the Lake City cases (run them through a neck-sizing S-die; trim to length; true the flash holes) and hand-throw and trickle your powder charges -- all steps not required for a semi-automatic rifle or carbine designed for combat and harsh field conditions.

Crimping raises your risk of core-jacket separation, which won't help your coaxial uniformity.

Do both rifles have the same round count? This may account for velocity variations and how much your jackets are getting roughed up in case-mouth to leades jump.

22.5 is a little low.
 
#12
Re: Help with huge standard deviation in handloads.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Leaddog</div><div class="ubbcode-body">Inconsistent powder charges.

Inconsistent seating depths. </div></div>

If that were the case you would think both guns would have huge standard deviations and velocity spreads. Same ammo used in both guns.
Pat
 
#13
Re: Help with huge standard deviation in handloads.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sinister</div><div class="ubbcode-body">Your groups are representative of semi-automatic rifles shooting unimproved brass.

For minimal Standard Deviation and Extreme Spread you're going to need to tune all cases for uniformity (like benchresters do). As recommended (even though new) you're going to need to tune the Lake City cases (run them through a neck-sizing S-die; trim to length; true the flash holes) and hand-throw and trickle your powder charges -- all steps not required for a semi-automatic rifle or carbine designed for combat and harsh field conditions.

Crimping raises your risk of core-jacket separation, which won't help your coaxial uniformity.

Do both rifles have the same round count? This may account for velocity variations and how much your jackets are getting roughed up in case-mouth to leades jump.

22.5 is a little low. </div></div>

22.5 grains is listed as the max in the manual I was using.
 
#14
Re: Help with huge standard deviation in handloads.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Alaskapopo</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sinister</div><div class="ubbcode-body">Your groups are representative of semi-automatic rifles shooting unimproved brass.

For minimal Standard Deviation and Extreme Spread you're going to need to tune all cases for uniformity (like benchresters do). As recommended (even though new) you're going to need to tune the Lake City cases (run them through a neck-sizing S-die; trim to length; true the flash holes) and hand-throw and trickle your powder charges -- all steps not required for a semi-automatic rifle or carbine designed for combat and harsh field conditions.

Crimping raises your risk of core-jacket separation, which won't help your coaxial uniformity.

Do both rifles have the same round count? This may account for velocity variations and how much your jackets are getting roughed up in case-mouth to leades jump.

22.5 is a little low. </div></div>

22.5 grains is listed as the max in the manual I was using.</div></div>

Use the manual as a good starting point, and work up a load to the rifle. Also, I've learned the hard way that loading on a dillon is not conducive to consistent powder throws unless you majorily tweak the powder thrower.
 
#16
Re: Help with huge standard deviation in handloads.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LawnMM</div><div class="ubbcode-body">If you aren't weighing each charge, that's your issue. </div></div>

That still would not account for why the good results from one gun and bad from the other. As an experiment I did hand weigh some loads a little while back and this is what I got.
77grainN135newbrasslarue.jpg

Going over my targets the brass seems to be the issue. These loads I tried with Remington once fired brass.
Larue77grainSierra8-2-11.jpg
 
#18
Re: Help with huge standard deviation in handloads.

The denominator for the equation for standard deviation is "n", the number of observations. You haven't told us how many observations were in each string, so a greater S.D. can be the result of fewer shots fired in a string.
 
#21
Re: Help with huge standard deviation in handloads.

Same load in two entirely different rifles, am I correct so far? I can also assume the barrels did not come from the same manufacturer?
Your loading problem is very simple. You cannot expect a load that produces low SD in one rifle, to produce the same numbers in a completely different rifle. I thought this would have been pointed out long before now. You have to develop different loads for different rifles. Your results have absolutely nothing to do with reloading practices beyond failing to tune a load to a specific rifle.
 
#22
Re: Help with huge standard deviation in handloads.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: armorpl8chikn</div><div class="ubbcode-body">Same load in two entirely different rifles, am I correct so far? I can also assume the barrels did not come from the same manufacturer?
Your loading problem is very simple. You cannot expect a load that produces low SD in one rifle, to produce the same numbers in a completely different rifle. I thought this would have been pointed out long before now. You have to develop different loads for different rifles. Your results have absolutely nothing to do with reloading practices beyond failing to tune a load to a specific rifle.</div></div>

You beat me to it - but I agree 100%....
 
#23
Re: Help with huge standard deviation in handloads.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: armorpl8chikn</div><div class="ubbcode-body">Same load in two entirely different rifles, am I correct so far? I can also assume the barrels did not come from the same manufacturer?
Your loading problem is very simple. You cannot expect a load that produces low SD in one rifle, to produce the same numbers in a completely different rifle. I thought this would have been pointed out long before now. You have to develop different loads for different rifles. Your results have absolutely nothing to do with reloading practices beyond failing to tune a load to a specific rifle. </div></div>

He's right. Unless the barrels are identical manufacturer, twist, length, and came off the line right behind each other your likelihood of one load working well in both is pretty slim.

All the lower spread means on the one rifle is that load is closer to being 'in tune' with that barrel. The fact that it produces a larger spread in the other rifle only confirms it is not 'in tune' with the other barrel.

I would focus more on the SD than the ES anyway. How far you stray from the baseline average is more important than the spread between the fastest and slowest rounds.
 
#24
Re: Help with huge standard deviation in handloads.

Pat, you are on the right track to finding an index load that both (or all) your .223 guns like.

I would submit your powder charges are still a little low. Having air space in your case means the powder in each and every round will settle differently and be exposed to the primer flash differently each time you shoot the rifle.

Whose load data are you using? Vihtavuori's N135 recommendations are slow (I doubt their bottom end charges for a 77-grain bullet will function some rifles). N135 is smack-dab in the middle of the IMR 4895-Varget-4064 medium rate burn range and is a solid national match performer. 23.5-24 is an average charge without having to compress your powder.

Crimping is not going to help with accuracy although it will improve your loading without bullet setback. A neck S-die and a .244 bushing is a better way to improve neck tension, keeping everything concentric and not putting a crimp in your jacket and possibly separating the core from the jacket.

A Stoney Point/Hornady LNL gage can help you check to find where your bullets are actually contacting your rifling leades in both guns. The compromise seating length is between both the Noveske's and Larue's cartridge overall length.

You could also try another type or brand of primers (perhaps a CCI BR4 or Winchester).

You'll find your load, it just takes some time. A group like the AMU needs an index load for 200+ uppers in varying states of wear to win.
 
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