I am loading for a .243 rpr. I have 2 loads i am checking out, both with a 105 rdf. 42.5 and 44.0. The 42.5 shoots really small groups (.2-.4) but has a high sd (15). I have not got the same groups from 44.0, but the last sd over 4 shots was 1.5 fps. Does a low sd actually show what the round is capable of, or should i go with the better 100 yard groups?
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Is sd a true sign of accuracy?
- Thread starter Forward543
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It's a sign of consistency (accuracy is different)
small groups at close range with a high SD doesn't mean squat at long range. standard deviation is basically how consistent your FPS is shot to shot.
Albiet, it also depends who you're talking to and what caliber / size target you're shooting at. PRS shooters typically don't need single digit SD's. You can get away with an SD of 20
shooting at MOA+ steel.
Bottom line if you want to tighten up ES/SD need to do proper load development. Don't know how you came about your loads but it doesn't sound like load development
small groups at close range with a high SD doesn't mean squat at long range. standard deviation is basically how consistent your FPS is shot to shot.
Albiet, it also depends who you're talking to and what caliber / size target you're shooting at. PRS shooters typically don't need single digit SD's. You can get away with an SD of 20
shooting at MOA+ steel.
Bottom line if you want to tighten up ES/SD need to do proper load development. Don't know how you came about your loads but it doesn't sound like load development
Try adj your seat depth with the higher charge, see what happens. Also, what shoots nice at 100 yards, may not be premium for 500 yards.
I worked up the load to get 44.0 grains. The 42.5 was a lower node i think, that has not got a full workup. I was just curious if the low sd's would prove to workout, or if i should adjust length/ primer at 42.5 to get better sd
I've come to the conclusion that low ES/SD mean little on their own when related to accuracy. I've known shooters who have shot single digit ESs with SDs in the 3s and have loads shoot between 1 and 2 MOA. I've also seen shooters with ESs around 20 with SDs around 12 put out loads that shoot in the 0.2s and 0.3s. I prefer to focus on a load's accuracy and let the numbers take care of themselves. Good, systematic load development and consistent reloading methods will help you accomplish both.
Where SD is going to play the biggest factor is downrange, not necessarily at 100 yards. Just playing around with AB WEZ Analysis, I put in the extremes of both accuracy and MV.
For example: All things being the same except MV and the "Rifle Precision", a gun holding 1 MOA but within 2fps of the input MV, it has a 93.61% chance of hitting a target at 1000 yards, however a a gun with .25 MOA but within 10 fps of the input MV, it has a 91.31% chance of hitting the same target.
For example: All things being the same except MV and the "Rifle Precision", a gun holding 1 MOA but within 2fps of the input MV, it has a 93.61% chance of hitting a target at 1000 yards, however a a gun with .25 MOA but within 10 fps of the input MV, it has a 91.31% chance of hitting the same target.
Really? Is that a serious question? Differences in MV, especially in high SDs, like what you see in a lot of factory ammo, is one of the biggest factors in elevation. Theres a lot of data that supports my statement. Im not just making shit up for the sake of post count or to make an argument. I know some shooters that will choose a load that has a higher MV and lower SD over a tighter shooting group. All I simply said is a lower SD is going to have a bigger impact at further distances. Yes single digit SDs mean consistency between each round, but it does not mean youre going to have a tighter group. Theres too many factors that come into play to just say lower SDs produce tighter groups, but it will mean less elevation differences between each round. Such as 9.8 mRad for 1 round and then 10.0 mRad for the next, not factoring human errors in fundamentals or wind, or accurate target distance, which all compunds together to create a huge flyer.
For a .2 mrad at 1K, the ES would have to be 40fps or greater.
Comparing your original post, let's say you take a 1moa accuracy gun to a match, the MD goes all out and sets a kyl rack at 1K, a 2moa plate, 1.5moa, 1moa, and a half moa plate, there is a slightly tricky wind, if your gun is a 1 moa gun, you better quit after the first plate, because now the 1.5 moa plate is not a given.
I'll take the accuracy load hands down any day, especially if I can somewhat control my horizontal shifts, 2 mrad at 1k is 7.2", where as 1moa gun, it's a crap shoot which direction your 1moa is going to go.
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That's one thing I don't like about the wez calculations. Not saying that you're regurgitating it but it gives many the wrong sense of conclusion.
Youre still hitting a 90+% rate at 1000 yards given certain parameters. And unless the gun is on a rail, no one is ever able to say with certainty that they missed their first round hit because of (insert reason)
KYL targets are an exception. Most steel targets out there are usually MOA+
people shoot matches all the time with factory ammo and score competitively well.
Youre still hitting a 90+% rate at 1000 yards given certain parameters. And unless the gun is on a rail, no one is ever able to say with certainty that they missed their first round hit because of (insert reason)
KYL targets are an exception. Most steel targets out there are usually MOA+
people shoot matches all the time with factory ammo and score competitively well.
All I'm saying is if you build a load that holds vertical at distance, get your seat depth down, and it's a win-win, too much emphasis on numbers, you know as well as I do, numbers fall into place if done right. Why not have the best of both worlds.
I've spotted for guys shooting moa or moa+ guns, at what point do you quit calling corrections and tell them to keep the same poa and fire away.
And one more, if your rifle is a 1 moa piece, 90% hit ratio a fucking pipe dream.
Back to the OP - no one mentioned it, but an SD taken over only 4 shots is meaningless. I wouldn't put ANY emphasis on that until you put a lot more of those rounds over the chrono. You are likely to find, regardless of all the other good considerations mentioned by others here, that you are chasing a load based on numbers that aren't real.
I believe that there are times when the best load for long range is a tighter-grouping load with a slightly larger SD, and there are times when the best load for long range is a slightly larger-grouping load with a tighter SD. The MAGNITUDE of these differences is what is important in choosing (you didn't say what the difference in the group sizes were). For example, if your 42.5gr load groups 0.3 avg, with a 15 SD, and your 44gr load groups 1.0 avg with a 1.5 SD (HIGHLY unlikely, but we'll assume), then take the 42.5gr load. If the 44gr. load groups around 0.5 and the SD is single-digit, then take it. If you can get your load to group 0.5 or better, and your SD near 10 or better, you have a load good enough that you can be confident isn't a factor in misses.
I believe that there are times when the best load for long range is a tighter-grouping load with a slightly larger SD, and there are times when the best load for long range is a slightly larger-grouping load with a tighter SD. The MAGNITUDE of these differences is what is important in choosing (you didn't say what the difference in the group sizes were). For example, if your 42.5gr load groups 0.3 avg, with a 15 SD, and your 44gr load groups 1.0 avg with a 1.5 SD (HIGHLY unlikely, but we'll assume), then take the 42.5gr load. If the 44gr. load groups around 0.5 and the SD is single-digit, then take it. If you can get your load to group 0.5 or better, and your SD near 10 or better, you have a load good enough that you can be confident isn't a factor in misses.
I got tired of chasing the smallest SD and the smallest groups at 100Y, seemed like I was chasing my tail half the time and it was a lot of work nailing down the best combination.
The vertical at distance is what I was most interested in, using a ladder test to show it. I started doing .1 or .2 grain increments for the ladder depending on the size of the cartridge case. Smaller case so .1 grain increments for 6x47, last test at 323Y showed 3 consecutive shots with almost no vertical, took 14 shots total IIRC. I didn't bother changing depth and SD was 6 fps which I found out later and was good enough for me.
A few months ago with the big gun, doing a ladder for it, two consecutive shots went into a half inch at 400Y. I picked the middle charge and was hitting a rock at 2055Y that was a foot tall and 1.5 feet wide quite often the next time out. Honestly I don't know the SD and backed the velocity in and stepped BC's to match come up's.
I could try to take load developement further but I don't care too. The final loads shoot well at 100Y but not excellent??? Always a point of controversy there. If I wanted all out 100Y accuracy I would be shooting a 6PPC with flat base custom bullets but that's not my game.
OP, see which loads have the least vertical at 400Y if possible. You can do seating depth at that distance too but for both pick a calm morning.
The vertical at distance is what I was most interested in, using a ladder test to show it. I started doing .1 or .2 grain increments for the ladder depending on the size of the cartridge case. Smaller case so .1 grain increments for 6x47, last test at 323Y showed 3 consecutive shots with almost no vertical, took 14 shots total IIRC. I didn't bother changing depth and SD was 6 fps which I found out later and was good enough for me.
A few months ago with the big gun, doing a ladder for it, two consecutive shots went into a half inch at 400Y. I picked the middle charge and was hitting a rock at 2055Y that was a foot tall and 1.5 feet wide quite often the next time out. Honestly I don't know the SD and backed the velocity in and stepped BC's to match come up's.
I could try to take load developement further but I don't care too. The final loads shoot well at 100Y but not excellent??? Always a point of controversy there. If I wanted all out 100Y accuracy I would be shooting a 6PPC with flat base custom bullets but that's not my game.
OP, see which loads have the least vertical at 400Y if possible. You can do seating depth at that distance too but for both pick a calm morning.
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Thanks for that, the op can also tweak seat depth from 400 - 1K, and the rifle will group respectable at 100, but will not be 1 bughole.
Ghengis kinda nailed it. SD is more about consistency. I don't pay attention to how things group at 100. Hell, if you're a decent shooter you can get almost anything to group at 100, but I will say that just because you have a low SD doesn't mean that load will shoot the tightest groups, it just means it will stay consistent.
For example......I just finished a new load work up for my 6.5 CM when I put a new barrel on it and switched to Lapua brass. I found 2 nodes that have me almost identical numbers. 42.0 and 42.6 both gave me very low SD's I the 3-4 and ES numbers in the 9-11 however the 42.0 did not group as well as the 42.6 at distance. It would still hold 1 MOA but the higher node grouped noticeably better even though they had the same numbers. It all comes down to a good load work up.
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For example......I just finished a new load work up for my 6.5 CM when I put a new barrel on it and switched to Lapua brass. I found 2 nodes that have me almost identical numbers. 42.0 and 42.6 both gave me very low SD's I the 3-4 and ES numbers in the 9-11 however the 42.0 did not group as well as the 42.6 at distance. It would still hold 1 MOA but the higher node grouped noticeably better even though they had the same numbers. It all comes down to a good load work up.
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Well that quarter minute gun with an SD of 20, is no longer a quarter minute gun at a grand, more along the lines of 3/4 MOA. You said it yourself, vertical dispersion is vertical dispersion, and youre not going to be able to account for difference in MV just like shooting a 1 MOA gun; maybe if youre always using a chronograph, but that will give you the reason after the fact for the high or low impact.
I like using the WEZ tool as an example, I know its not the end all, be all; but its a more accurate baseline than some guys experience or opinion.
Lets put it in realistic terms; a 1/4 MOA gun with an SD of 20 meaning 68% of the MVs are within +/-20fps, and 95% are within +/-40fps, then 99.7% are within +/-60 fps, is going to have an uncertain vertical dispersion of +/-7.5", 66% chance hitting a 10" gong at a 1000 yards, but with 1/2 MOA gun with and SD of 10, meaning 68% of the MVs are within +/-10 fps, 95% within +/-20 fps, then 99.7 within +/-30 fps, is going to have an vertical dispersion of +/-3.7", 84% chance hitting a 10" gong at a 1000 yards.
This is realistic, no one should accept a 1 MOA gun especially if theyre handloading, but choosing between 1/4 MOA and 1/2 MOA, not a huge difference between the two, but examining the SDs and ESs for each load should determine which load you go with.
By all means keep loading for the tighter group with high SDs, youre not hurting my feelings.
I don't know why this thread turned into a pissing contest.
You load to your discipline.
if you're a 300yd BR shooter and your tightest group turns or to be bad ES/SD then you keep that.
If youre shooting for distance where youre approaching the transonic zone then you you need to aim for better SD's. If you're shooting ELR Then there's no exceptions you need your SD's to be as low as possible.
As far as group size goes that's independent of MV, you strive to get small group size with good numbers
You load to your discipline.
if you're a 300yd BR shooter and your tightest group turns or to be bad ES/SD then you keep that.
If youre shooting for distance where youre approaching the transonic zone then you you need to aim for better SD's. If you're shooting ELR Then there's no exceptions you need your SD's to be as low as possible.
As far as group size goes that's independent of MV, you strive to get small group size with good numbers
When did I say any of my loads have a high sd number, my statement is I would not build a load off a chrono, pure and simple. But, look to the benchrest world and you will never hear this argument, proof there is on paper, way tighter groups than I shoot, I'm banking you too.
Besides, get on your kestrel and change mv + or - 10fps, it will be 1/10th mil in dope, half either way, which in my book means 1.8" either way.
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Shot the loads again, with a length test for the 42.5. I found a better length for the 42.5, that gets good accuracy as well as lower sd's. (.3's with a 6.9 sd) the velocity is only 2800 fps, but with 105's should get me close to 1200 yards. I think i must have fucked up my test for ocw, and still needed to run higher to find the next node. Either way, ill run this barrel out with the 42.5, as im 800 rounds in to a .243, and would still like to use it. Thanks for everyones experience.
GhenghisAhn175; Agreed, different methods to load for different applications. My statement was simple stating that loading to lower SDs was better for LR.
You didnt, just what your statements implied. At least the way I interpreted them. BR is a whole different monster compared to LR. But LR is more than likely implicated here rather than BR for the simple fact that this is a "sniper" forum, and not a benchrest forum, though it is widely discussed here, but not the main topic of discussion here.
Youre right its only .1 mRad, but thats not factoring in accuracy of the range to target, wind velocity (which does factor in some elevation dispersion), temperature both powder temp and atmosphere temp, baro, fundamentals, etc. You factor all that into your 0.1 mRad dispersion youre looking at +/- 0.2-0.3 mRad of vertical dispersion. And thats with a SD of 10, you start increase that SD to 15-20, youre looking at major changes in dispersion.
Which for LR, having 1/4 MOA vs 1/2 MOA gun is negligible, but having consistent MV is more practical if youre having to choose between a 1/4 MOA and 1/2 MOA or even 3/4 MOA load.
A few references to support my statement:
http://precisionrifleblog.com/2015/04/18/how-much-does-sd-matter/
http://precisionrifleblog.com/2015/04/15/how-much-does-group-size-matter/
https://youtu.be/ACyfeeBHVOA?t=508
You didnt, just what your statements implied. At least the way I interpreted them. BR is a whole different monster compared to LR. But LR is more than likely implicated here rather than BR for the simple fact that this is a "sniper" forum, and not a benchrest forum, though it is widely discussed here, but not the main topic of discussion here.
Youre right its only .1 mRad, but thats not factoring in accuracy of the range to target, wind velocity (which does factor in some elevation dispersion), temperature both powder temp and atmosphere temp, baro, fundamentals, etc. You factor all that into your 0.1 mRad dispersion youre looking at +/- 0.2-0.3 mRad of vertical dispersion. And thats with a SD of 10, you start increase that SD to 15-20, youre looking at major changes in dispersion.
Which for LR, having 1/4 MOA vs 1/2 MOA gun is negligible, but having consistent MV is more practical if youre having to choose between a 1/4 MOA and 1/2 MOA or even 3/4 MOA load.
A few references to support my statement:
http://precisionrifleblog.com/2015/04/18/how-much-does-sd-matter/
http://precisionrifleblog.com/2015/04/15/how-much-does-group-size-matter/
https://youtu.be/ACyfeeBHVOA?t=508
Gosh, what you have works, I was trying to calculate in my head what powder you were using off your chrono numbers is all. From H4350 to H1000 will do fine in a 243. If it was my gun, I would put more powder in and try get it north of 3000fps, just me.
Also I'm sorry your post got hijacked into a dick measuring contest, we all have a diff route to an end product.
Ok, if it were mine, I would have started out with H1000, or IMR 7977, run the slowest powder that will yield some speed at a reduced pressure, saves on throat wear. But only would I use H1K if the rifle was not suppressed, if suppressed, H1K not a good choice. Right now you have a good amount of rds down the barrel and it would be wise to stay the coarse.
But in the future if you rebarrel to the same, start slower powder, then when you get what I call a pressure dump, loss of speed because of throat wear, being it back to life with 4831 to finish the barrel off.
I am running supressed. Ill stay the course for the rest of this barrel. And dont sweat the pissing match, its better to hear theory and pick what you can from it, than to have someons bullshit they vomitted without actual experience.
I will never consult AB wez on the probability of making a hit on a plate at 1K to judge my loads performance, I'll just hit it. With modern day tools, a Kestrel 5700 with AB, your wind reading skills will be the deciding factor. To judge your loads performance, after hitting the plate, follow it up with a centering hit, or better yet, pound it 3 times and look at the dispersion.
You develop your load, using your chrono as a tool instead of the sole base of data gathering, get where you can shoot a group under 1.5" at 500 yards, it will carry to 1K, then re-chrono and you will find your es and sd numbers have shrunk to just where you want them to be, numbers all have to do with your load being in a pressure range that your platform likes, it is really simple if you're willing to pay your dues.
I would not use 100 yards as an indicator for anything unless all I was going to do is shoot 100 yard groups.
I've seen terrible SD shoot great 100 yard groups but the same certainly didn't hold when same loads were tried at beyond 300 yards.
I've seen terrible SD shoot great 100 yard groups but the same certainly didn't hold when same loads were tried at beyond 300 yards.
I apologize as well, OP, things got a little carried away; I was just trying to save you time, frequent trips, and money for developing loads for LR. If it works, it works no need to fix it, but theres always ways to improve and to be more efficient.
Using computer or mobile programs for real world applications is always going to be subjective, that includes Quickload, ballistic calculators, etc.
Using computer or mobile programs for real world applications is always going to be subjective, that includes Quickload, ballistic calculators, etc.
