View Full Version : Single Digit Standard Deviations (SDs) and Teen Extreme Spreads (ESs)
One of Molon's posts has me working on improving my reloading process.
My current best loads average an Extreme Spread (ES) of 55 and a Standard Deviaiton (SD) of 17 when reloading .223/5.56mm over 3 100 round strings of fire.
The best repeatable performance my loads have ever done is an ES of 40 and SD of 10 over 10-round strings.
Molon's reloads have teen ES' and single digit SDs. Although some of my loads will shoot slightly sub-MOA, it's not consistent.
My question is for anyone who also reloads ammo to this precision, what is your equipment and/or process for doing so?
I'm doing the following:
1.) Deburring flash holes
2.) Truing primer pockets
3.) Cleaning primer pockets
4.) Camphering and deburring case mouths
5.) Trickling to an exact weight on a higher end digital scale with +/- .1 grain claimed accuracy
6.) Sizing/seating on a single stage press with competition dies
This is for match/long range ammo with Sierra Match Kings or similar bullets and Lake City brass weighed to be kept in 100 round lots with an extreme spread of .5 grains. Primers are CCI #41.
I'm a little lost as to what to do to improve my ammo, other than anneal case necks. I think I've done the best I can do with my equipment, and either need a new process, new equipment or new components.
Maybe try BR4 bench rest primers for a more consistent ignition? I've had good luck with them group wise but only check velocities when switching lot#'s for my loads.
I wonder if single loading a 10 rd string would show less variation then loading from the magazine?
Try varying the actual load. Try a few tenths of a grain either way. Tune the load to your gun.
Try varying the actual load. Try a few tenths of a grain either way. Tune the load to your gun.
I've tuned the snot out of them.
With the components (powder/primers) I've used, I never achieved any consistencies close to that of Molon.
Try a different powder, or brand of primer.
What is your end goal? Increased accuracy? If so, at what distance are you shooting?
Increased accuracy is my goal.
My loads (and I) average 1 MOA now at 1-200 yards over multiple 10-shot strings. I only sporadically get the opportunity to shoot any greater distances out to 600 yards, as it's a 2-hour hike.
However, I assume with tighter ES', I will have less vertical stringing at all distances.
I don't know if you're going to see much improvement over 100-200 yards by tightening up your ES/SD values. I could see it at longer ranges, but 1 MOA is pretty good right now.
If you still want to pursue this I would recommend you look at a couple things in your process:
(1) Controlling neck tension. Annealing necks if necessary, don't assume the neck tension provided on a new, or once fired case, will be the same as a case loaded for the 5th-6th time. Case necks work harden and the amount of spring abck from resizing varies as the hardness varies. Either get a bushing die or anneal necks to provide consistent hardness.
(2) Pick a good bullet. I'm assuming with 1 MOA results to date, you're already there, but don't expect great accuracy from 55 grain FMJ-BT plinkers.
(3) Pick a good powder. Iv'e read good reports lately from IMRs 8208. It's a small grain extruded powder, and I think you'll get slightly better accuracy from extruded than from ball. If shooting 77s, HP shooters for years have had good results with RL-15 or Varget.
(4) Shooting technique. Use a solid rest. Pay attention to the crosswind. Use good trigger control and follow through.
(5) Shoot through a clean bore, not necesssarily white glove inspection clean, but don't expect sub-moa groups through a bore that has had hundreds of rounds through it w/o cleaning. And if load testing using multiple powders, clean between powders. Lots of loads don't shoot well at first when you change powders.
(6) Use a good trigger. I don't expect great results using a mil spec trigger. It might be achievable, but it's so much easier if you are using a good trigger to begin with.
Good luck and please report back with your findings.
1.) Yes, that's all I have left to try, aside from switching primers. I'm thinking of buying the Redding Type S bushing die with a few bushings for adjustment as the brass work hardens. Much of my current brass is on its second or third firing.
2.) Already use SMKs or an equivalent bullet. Haven't tried V-max's at these shorter distances, though. I've heard sometimes those shoot better at 100 yards than SMKs.
3.) Tried a few. Varget, RE-15, H335, BCL-2, W748. RE-15 seems to shoot the best so far with a light charge under 69 gr SMKs. Best load this weekend shot .88 over 10-rounds, but averaged 1.01 MOA over 50 rounds in 5 strings. Varget was slightly worse. Again, this may be more of a comment on my shooting ability than the potential of the load, but I'd still like to improve my reloading process.
4.) Yup. I could use a better rear bag. The Caldwell I have doesn't work too well with the EMOD. Not sure what will, though.
5.) Guilty. I'll shoot 100 rounds without cleaning. Sometimes, rarely alternating different powders when testing loads like this weekend.
6.) Have a decent one, a 3 lb Timney. Switched my SSA that I was using, and my groups have improved slightly.
Still, my best ES today was 37 with an SD of 10.6. Not exactly stellar numbers.
I'd still like to learn how to get single digit SDs repeatably. :confused:
I think Molon mentioned once that he was using a Vihtavuori powder. In my limited experience (pistol ammo) the VV powders do produce tighter SD and ES than most other powders.
I've also noticed that as charge weight is increased from starting value ES tends to tighten up as charge is increased.
I think Molon mentioned once that he was using a Vihtavuori powder. In my limited experience (pistol ammo) the VV powders do produce tighter SD and ES than most other powders.
I've also noticed that as charge weight is increased from starting value ES tends to tighten up as charge is increased.
Molon also stated for his 77 SMK load, along with Vihtavuori, he used new LC brass and Fed 205M primers. Changing from Rem 7 1/2 to Fed 205M, I've brought my SD down from the mid teens into the 9's.
Mizer67
Review a ballistic calculator, and look at the numbers.
A minute of angle = yds x .010472”. So, for 200 yds, a minute of angle = 2.1”, etc.
With a 37 ft/sec ES (77 gr. SMK) , at 200 yds, you have a drop of .3” (1/3”) between 2650 and 2687 ft/sec. This is about 1/7 of a MOA (with 0 at 50yds). At 600 yds, with a MOA of 6.28, you have a drop of 4” or 2/3 of a MOA because of your ES. That’s not that bad, and up to about 300 yds, really not a factor in accuracy or vertical stringing. If you can put 10 rds into one MOA at 100 and 200 yds (MOA for 100 yds = 1.04”), you’re doing pretty good, I’d say.
If you are looking to lower your ES, it seems the first thing most serious long range shooters do is weigh new brass. I suggest weighing your brass and loading brass within groups of 1 gr. from the same lot. Buy some new Lapua or Winchester brass, separate it by weight, deburr the flash holes, and see what happens. Some long range shooters weigh to within ½ gr, and they even separate their bullets by weight.
I’ve had the same ES/SD from dropping my powder as weighing it on an electronic scale. I own an electronic scale, and I believe unless you pay hundreds of dollars for a very expensive scale, you won’t get the same accuracy as from a manual balance beam scale. Try trickling powder using a balance beam scale and do it the same way every time.
Also, your chronograph might not be up to the task. Use another Chronograph to confirm your results.
Good luck.
Mizer67
Review a ballistic calculator, and look at the numbers.
A minute of angle = yds x .010472”. So, for 200 yds, a minute of angle = 2.1”, etc.
With a 37 ft/sec ES (77 gr. SMK) , at 200 yds, you have a drop of .3” (1/3”) between 2650 and 2687 ft/sec. This is about 1/7 of a MOA (with 0 at 50yds). At 600 yds, with a MOA of 6.28, you have a drop of 4” or 2/3 of a MOA because of your ES. That’s not that bad, and up to about 300 yds, really not a factor in accuracy or vertical stringing. If you can put 10 rds into one MOA at 100 and 200 yds (MOA for 100 yds = 1.04”), you’re doing pretty good, I’d say.
If you are looking to lower your ES, it seems the first thing most serious long range shooters do is weigh new brass. I suggest weighing your brass and loading brass within groups of 1 gr. from the same lot. Buy some new Lapua or Winchester brass, separate it by weight, deburr the flash holes, and see what happens. Some long range shooters weigh to within ½ gr, and they even separate their bullets by weight.
I’ve had the same ES/SD from dropping my powder as weighing it on an electronic scale. I own an electronic scale, and I believe unless you pay hundreds of dollars for a very expensive scale, you won’t get the same accuracy as from a manual balance beam scale. Try trickling powder using a balance beam scale and do it the same way every time.
Also, your chronograph might not be up to the task. Use another Chronograph to confirm your results.
Good luck.
I ponied up the dough for a Hornady Autocharge for this task (match ammo), and based on the reviews I read, I thought I was getting a good deal.
I'm not impressed so far obviously, and it tends to drift between a tare weight of 136.6 and 136.8 grains for my scale pan.
I guess you can pay more, but not neccessarily get more with an electronic scale/charger combo. Seems like I have a range of +/- .2 grains to account for my ES, if it's related to powder charge, which it may or may not be (+/- .1 grains in drift alone). I haven't used my balance beam scale in years, but it may be time to drag it out and dust it off.
I already weighed my brass in 1 grain lots, so that's not going to help unless I go down to .5 grains. 205Ms (and new brass) are something I need to try.
Good point on the chrony though. I think it's rated for 1% accuracy. At 2,700 fps, that's 27 fps right there. I guess that's another "you get what you pay for" type of item. Mine was $89, and probably isn't going to cut the mustard for this type of test.
Also, I hear what you're saying about MOA, and I know vertical stringing at this distance is shooter induced. However, I'm simply in an interesting and slightly obsessive quest to produce the highest quality ammo I can for service rifle, so I have no excuse but to improve my shooting ability. ;) My average ES is also more like 47.2 fps, with an SD of 14.4, so it's slightly worse than I stated above (that was my best 10-round string from my latest testing). The load still shoots an average of 1.01 MOA over 100 rounds, however, so it's at least a statistically significant sample.
Am I the only one who snickered when I saw the words "teen extreme spreads" on a thread title?
eightmillimeter
12-08-10, 17:14
The only step I haven't seen mentioned yet is measuring the weight of the cases and sorting them by weight. I started doing that a long time ago and it makes a big difference, more so than sorting by lot # etc.
1_click_off
12-08-10, 18:04
I am not familiar with your electronic scale, I still have a balance beam. But I do know that just simply having a ceiling fan on can throw your scale off. Make sure your fan is off, A/C vent is not pointed at your load bench, and if you can take a cardboard box and cut it out to suround your scale to keep any wind off of it. This may sound extreme, but in my work we have certified electronic scales and some even have a plexiglass enclosure that you can totally seal the scale from any wind.
Another tip for digital scales to control slight drift (even unnoticed by the 'zero' remaining unchanged on the display: reset the scale by either taring or turning off, then back on (with the powder tray placed on it)...then immediately weigh the charge. You may be surprised how you can get up to a couple tenths of a grain difference in reading without realizing your zero had drifted.
I am not familiar with your electronic scale, I still have a balance beam. But I do know that just simply having a ceiling fan on can throw your scale off. Make sure your fan is off, A/C vent is not pointed at your load bench, and if you can take a cardboard box and cut it out to suround your scale to keep any wind off of it. This may sound extreme, but in my work we have certified electronic scales and some even have a plexiglass enclosure that you can totally seal the scale from any wind.
http://www.midwayusa.com/viewproduct/?productnumber=818489
Comes with a draft shield. The shield doesn't make any difference with the drift. I tried putting it on a line conditioner (cleaner, more stable power) and that didn't help. Then I tried attaching a UPS to the line conditioner (again, more stable power source), that didn't work either. It just likes to drift.
I think Hornady just cheaped out and skipped out the dampening and on the strain gauge. Warming up for 24 hours plus doesn't help consistency either.
I also placed the scale on a vibration dampening pad and have it on a separate table on a piece of granite. Vibe is not the issue.
I think I've isolated all possible environmental causes, and still can't mitigate the drift issue. Not my first digital scale, and I've done my best to provide stable conditions for repeatable results.
Another tip for digital scales to control slight drift (even unnoticed by the 'zero' remaining unchanged on the display: reset the scale by either taring or turning off, then back on (with the powder tray placed on it)...then immediately weigh the charge. You may be surprised how you can get up to a couple tenths of a grain difference in reading without realizing your zero had drifted.
I recalibrate, re-zero and tare the scale pan every 25 rounds. It's a PITA, but it would minimize the drift the scale can incur over that short period of time (maybe 10-15 minutes). However, it's still not enough to reduce the ES and SDs of my loads.
Just placed a primer/powder order with PVI, so in the next few weeks I'll be testing RE-15 with SMKs and a new lot of Lapua brass, varying the charge and the primer. I've got Federal 205 GMM, CCI SR, Wolf SR, and Rem 7 1/2's on the way, so we'll see if those help improve consistency.
I'd just hit the zero button inbetween weighing cycles.
If you throw light and trickle up, recognize that the software in these scales doesn't respond well to minor weight adjustments. Meaning, you're trying to trickle up the last .2g, you trickle and trickle and trickle and the scale doesn't register the weight. Then all of a sudden it will register a .3-.4g jump.
That's why when I trickle, I remove the pan, trickle a bit, and then place the pan back on the scale. If I get within + .1g, I declare victory and charge the case. Getting it nailed to the exact tenth just doesn't matter.
I'd just hit the zero button inbetween weighing cycles.
If you throw light and trickle up, recognize that the software in these scales doesn't respond well to minor weight adjustments. Meaning, you're trying to trickle up the last .2g, you trickle and trickle and trickle and the scale doesn't register the weight. Then all of a sudden it will register a .3-.4g jump.
That's why when I trickle, I remove the pan, trickle a bit, and then place the pan back on the scale. If I get within + .1g, I declare victory and charge the case. Getting it nailed to the exact tenth just doesn't matter.
The Autocharge is a combination unit like the RCBS Chargemaster. It trickles each charge up automatically to weight then stops.
Zeroing the scale after each charge isn't practical. The unit will begin to dispense the next charge the way I have it set up, as it'll now read zero.
Also, it serves no purpose as most scales like this one (and yours most likely) are programmed to "hunt" for zero anyway.
There's no "zero" button?
I use a PACT scale, but it's just a scale, no dispensing. I've checked it against my balance beam and using RCBS check weights and it's accurate enough for me. Whenever the empty pan reads anything other than zero, I just hit the button and it re-zeroes it in just a couple of seconds.
Mizer67
Weigh 10-15 charges on your electronic scale and then weigh them on the beam scale. This might be a way to confirm the accuracy of your electronic scale.
However, I did this yesterday, and was surprised at the difference.
There's no "zero" button?
I use a PACT scale, but it's just a scale, no dispensing. I've checked it against my balance beam and using RCBS check weights and it's accurate enough for me. Whenever the empty pan reads anything other than zero, I just hit the button and it re-zeroes it in just a couple of seconds.
No, of course there's a zero button.
However, zeroing the scale would erase the tare of the scale pan, and with the auto-dispense function would cause a charge to drop onto an empty scale pan, as the system believes the scale pan has been returned to the scale at that point.
Mizer67
Weigh 10-15 charges on your electronic scale and then weigh them on the beam scale. This might be a way to confirm the accuracy of your electronic scale.
However, I did this yesterday, and was surprised at the difference.
I can confirm that my scale is not as repeatable as it should be, that's about it. Either that or my beam scale isn't giving repeatable results.
No, of course there's a zero button.
However, zeroing the scale would erase the tare of the scale pan, and with the auto-dispense function would cause a charge to drop onto an empty scale pan, as the system believes the scale pan has been returned to the scale at that point.
Maybe I'm just not following you. On my scale, I zero the scale with the pan in place. That way the scale takes the weight of the empty pan into account. When the pan is removed, the scale reads something like -127.0g, but when I place the empty pan on the platten the scale should read 0.0g, if it's properly zeroed. If it reads something like 0.1g, or -0.1g, I hit the zero button with the pan still on the platten and it will then read 0.0g. At that point I would then dispense a thrown charge into a case and then pour this into the empty pan to get a weight on the powder charge.
What I'm asking/suggesting is, if you are experiencing zero drift, rezero the scale with an empty pan on the platten. Then when the measure dispenses the programmed weight, it should be against a "zeroed" reference.
Lastly, before I do anything during a reloading session, I go through a calibration process, which doesn't involve the pan at first. It involves a couple of known check weights, but the last step of the process, once calibration is completed, is to zero the scale with an empty pan on the platten. I guess I'm assuming all electronic scales function in this manner.
Hope this is in some way helpful, am not trying to be a pest.
Maybe I'm just not following you. On my scale, I zero the scale with the pan in place. That way the scale takes the weight of the empty pan into account. When the pan is removed, the scale reads something like -127.0g, but when I place the empty pan on the platten the scale should read 0.0g, if it's properly zeroed. If it reads something like 0.1g, or -0.1g, I hit the zero button with the pan still on the platten and it will then read 0.0g. At that point I would then dispense a thrown charge into a case and then pour this into the empty pan to get a weight on the powder charge.
What I'm asking/suggesting is, if you are experiencing zero drift, rezero the scale with an empty pan on the platten. Then when the measure dispenses the programmed weight, it should be against a "zeroed" reference.
Lastly, before I do anything during a reloading session, I go through a calibration process, which doesn't involve the pan at first. It involves a couple of known check weights, but the last step of the process, once calibration is completed, is to zero the scale with an empty pan on the platten. I guess I'm assuming all electronic scales function in this manner.
Hope this is in some way helpful, am not trying to be a pest.
Yes, I'm sure I'm just not making myself clear.
Every electronic scale that I've seen will have a tare capability. You set some weight, like a scale pan, on a scale that reads "0.0" and hit the zero button, you'll get a negative number when that weight (like the scale pan) is removed.
What I'm saying is that with the low-end strain gauge technology all current reloading scales are based on will drift. Some will appear not to, but that is only the programming (and possibly readability) of the scale masking the issue.
Also, because it is not possible to weigh powder charges accurately to the division we require for reloading with current strain-gauge technology, software programming is written to interpret the signals the strain gauge is giving off and enable the scale to give a read out in tenths of a grain.
Since these low-end scales we use drift by design, part of the software code is written to make the scale "hunt" for zero. Meaning, when the scale reads close to 0.0, the scale interprets any additional weight as an error, and returns to zero automatically. This is what my scale will do when the scale pan is returned to the scale. It may weigh .1 or .2 grains over when the pan first touches down, but will eventually (in 3-4 seconds or less) return to zero on it's own.
Also, most scales will have programming that make them "lock-on" to a value, which makes them fail to interpret trickling of additional powder accurately. If you want to spend ~$650 - $900 or more, you can get a true analytical balance that has magnetic dampening and other technology to minimize drift and aid in accurate trickling, however, not many of us can afford that type of equipment and it's not truely neccessary.
Therefore, because of the imperfect technology available at this $30-$600 price point, "zeroing" the scale again (actually taring the weight of the pan again) is not improving the drift, as the scale will automatically fix this issue through it's software code. It could actually be making the problem worse if done repeatedly.
Also, at least with my scale, the calibration routine does not eliminate or reduce the drift for longer than 30 seconds or so, even with the draft shield in place. The -136.8 grain tared reading for my scale pan won't stay displayed for long before the drift takes over and it drops to -136.7 or increases to -136.9, etc.
OK, I'm following along with what you're saying. I've experienced much of what you say with my PACT. However, I do question the following:
Therefore, because of the imperfect technology available at this $30-$600 price point, "zeroing" the scale again (actually taring the weight of the pan again) is not improving the drift, as the scale will automatically fix this issue through it's software code. It could actually be making the problem worse if done repeatedly.
My experience has been sometimes the software doesn't eliminate the drift. It will stay stuck on + 0.1g, and that's when I rezero it. Doesn't happen too often, but it can happen every 15-20 weighings.
Secondly, when I first got it and was trying to learn its idiosyncracies, I would occasionally compare weights displayed on the PACT with weights provided by my balance beam. As long as the scale was zeroed before weighing a charge, and by that I mean the display read 0.0 on an empty pan, the weights from the PACT the majority of the time agreed with my balance beam, and on the few occasions they didn't, it was never off by more than 0.1g. That's close enough for me. It got to the point that I trusted it enough I stopped checking it against my balance beam.
One last thing, the power source for my PACT is battery. I'm guessing that's a cleaner source than AC. If you run yours on AC, and it has battery capability, you might try switching over and seeing if that helps your drift.
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