Importance of STD Deviation of velocity with repesct to accuracy?

[kujuak]

Since I was gifted a Garmin chrono I have been learning alot about my reloads. I am amazed that my reloads have a better STD deviation velocity results than factory ammunition in almost every instance.I chronographed some Federal Gold Medal match ammo to determine velocity in my rifle to help direct my reloading efforts. The STD Deviation values surprised me as they were much higher than I see with my reloads. My reloading technique is much crude than most here employ (I don't sort bullets /cases)by weight, no neck turning or doing things to flash hole, powder charges are by RCBS Chargemaster, and so on).

 

[JEFFPPC]

I watch extreme spread. Not sure it all means as much as some think.

 

[kujuak]

I watch extreme spread also.But I think getting STD<5 reflects a low extreme spread variation. (This is when looking at shot strings of 6-10 shots).I am going to look and see if there is any good data comparing the relative importance of these to measurements with regards to accuracy, especially at distance.
Thanks for your thoughts!

 

[jelenko]

Kinda says that standard deviation of velocity is essentially unrelated to accuracy - at least at distances less than 1k yards.

 

[Jager]

Extremely consistent velocity, as reflected in very small standard deviations, is important in long range. A whole lot less so at the shorter ranges most of us shoot.

My own personal take is that standard deviation gives some insight into how dialed-in one's reloading practices might be; but gives precious little hint of how accurate, or not, a particular load is.

There are lots of loads out there with pretty unimpressive SD's that shoot dots.

 

[RabbitSlayer]

My loads also beat factory ES\SD without doing anything too fancy. I cut factory hornady match ammo ES in half with the same brass, same bullet, I bet they also use H4350. Almost no load development. Backed off jam .020, tested a couple powder weights, thats it.

What it really tells us is the word "match" on the box doesn't mean anything.

I don't think the numbers matter till after 300 yards. At least that is what the PDs seem to think. At 1000 I simply like that I know the problem is me and not my lousy gear.

 

[rardoin]

Zero STD's are definitely the way to go. Kinda ties into to the 'Private vs Pubic' range thread....don't ya' think?

 

[kujuak]

Zero STD's are definitely the way to go. Kinda ties into to the 'Private vs Pubic' range thread....don't ya' think?

Could you be so kind as to explain the comment,I am not familiar with the discussion about ranges and it's connection to attaining my accuracy goals.
Thank you.

 

[IAm_Not_Lost]

Could you be so kind as to explain the comment,I am not familiar with the discussion about ranges and it's connection to attaining my accuracy goals.
Thank you.

The less STD's you have the better. The more STD's you get the more chance you'll have to....spread....

 

[kujuak]

To be clear, my goal is developing an accurate load for my 300 WinMag hunting rifle, maximum range of use is 500-600yds depending on the accuracy I can achieve.With the costs of components, especially premium bullets I am looking for the most important variables/data to heed.My best cup /core bullet load gives me sub 1'groups at 100yds but 6-7 inch groups at 300yds. My best load with Nosler partitions gives me 1.25" 100yd groups but 4-5" groups at 300yds. I spent 6hrs yesterday at the range confirming these findings. The range is a ?public range (you have to be member to gain access) that is 60 miles from the nearest town and has 3 shooting points.I
load 308 ammo for a heavy barrel AI rifle for shooting out to 1200yds so far .BUT that rifle weighs 20lbs and I shoot it for fun. I consider (for me at least) ethical hunting ranges go to 500, maybe 600 yds max.
All advice will be humbly considered.
thanks!

 

[rardoin]

Just ignore me, I was making a joke about sexually transmitted diseases (STD's) and another thread that misspelled 'Public' ranges (an absent L changes things....LOL). Yes, it is normal to expect to be able to get your Extreme Spreads (highest and lowest velocity in a string) as well as Standard Deviation (variation about the mean velocity) much less than factory loads. The factory loads are formulated to be shot in any rifle chambered to the SAAMI spec for that cartridge. As a reloader, you have the luxury of fine tuning the load for your specific rifle. Fun, Isn't it? You stand a great chance of getting sub MOA loads at 300-500yds if you work methodically and have good technique behind the rifle.

 

[kujuak]

The less STD's you have the better. The more STD's you get the more chance you'll have to....spread....

Sorry for any confusion, By STD I meant Standard Deviations in velocity. As for STD's, my only involvement in that area has been in the diagnosis and treatment of those ailments and their sequelae.

cheers!

 

[Webster]

My loads also beat factory ES\SD without doing anything too fancy. I cut factory hornady match ammo ES in half with the same brass, same bullet, I bet they also use H4350. Almost no load development. Backed off jam .020, tested a couple powder weights, thats it.

What it really tells us is the word "match" on the box doesn't mean anything.

I don't think the numbers matter till after 300 yards. At least that is what the PDs seem to think. At 1000 I simply like that I know the problem is me and not my lousy gear.

Match just means they charge more $. Maybe a little better QC. We all know what shoots well in one rifle may not shoot well in another. You cannot tune a factory load.

 

[Laurie]

By STD I meant Standard Deviations in velocity

I reckon most people recognised that. Those words are invariably abbreviated to 'SD' in shooting / ballistics / statistics usage, hence the temptation to deliberately read it as having the other meaning, where 'STD' is the norm .

 

[kujuak]

I guessed that, I'll see if I can ncorrect my post. I have gotten in the habit of writning just "STD" in my range notes when I'm writing down my chrono readings as the chrono lists this value under "STD DEV".

 

[RegionRat]

Kinda says that standard deviation of velocity is essentially unrelated to accuracy - at least at distances less than 1k yards.

Well, I agree but it starts to show sooner than this when the noise level is low enough to expose it. A competitive Mid Range match gun or LR BR rig can show the vertical associated with SD/ES much sooner than 1000 Y and typically it is easy to read at 600.

 

[RegionRat]

To be clear, my goal is developing an accurate load for my 300 WinMag hunting rifle, maximum range of use is 500-600yds depending on the accuracy I can achieve.With the costs of components, especially premium bullets I am looking for the most important variables/data to heed.My best cup /core bullet load gives me sub 1'groups at 100yds but 6-7 inch groups at 300yds. My best load with Nosler partitions gives me 1.25" 100yd groups but 4-5" groups at 300yds. I spent 6hrs yesterday at the range confirming these findings. The range is a ?public range (you have to be member to gain access) that is 60 miles from the nearest town and has 3 shooting points.I
load 308 ammo for a heavy barrel AI rifle for shooting out to 1200yds so far .BUT that rifle weighs 20lbs and I shoot it for fun. I consider (for me at least) ethical hunting ranges go to 500, maybe 600 yds max.
All advice will be humbly considered.
thanks!

The SD/ES isn't the place to spend too much effort in this context. However to qualify this statement, you can't load slop either.

Try to spend your time on field shooting and wind, and you will be much better between 300 - 600 yards.

There was a video that some of my old colleagues pointed out to me recently. I tend to get bored if I use the stationary bike at home so I watched it while working out on the bike. If you are new at this game, it may be worth your time to watch it, so I'll try to dig up the link.

The guy spends some time explaining his use of the AB Analytics program and how he games and budgeted what you should weight for a typical big game hunting rig in terms of where to spend your time and what is a waste of time.

If you make a kill zone size assumption and then game the AB program to explore what makes you more likely to hit at 600 yards, you will see that getting really small groups and really tight SD/ES isn't the most important use of your time. I found that video, here is the link.

 

[Uncle Bruce]

Well, I agree but it starts to show sooner than this when the noise level is low enough to expose it. A competitive Mid Range match gun or LR BR rig can show the vertical associated with SD/ES much sooner than 1000 Y and typically it is easy to read at 600.

If you intend to shoot at 600 or 1000yd you should tune at that distance.
A lot of the time it will not be the 200 yard load that would be best for the longer ranges.

 

[kujuak]

The SD/ES isn't the place to spend too much effort in this context. However to qualify this statement, you can't load slop either.

Try to spend your time on field shooting and wind, and you will be much better between 300 - 600 yards.

There was a video that some of my old colleagues pointed out to me recently. I tend to get bored if I use the stationary bike at home so I watched it while working out on the bike. If you are new at this game, it may be worth your time to watch it, so I'll try to dig up the link.

The guy spends some time explaining his use of the AB Analytics program and how he games and budgeted what you should weight for a typical big game hunting rig in terms of where to spend your time and what is a waste of time.

If you make a kill zone size assumption and then game the AB program to explore what makes you more likely to hit at 600 yards, you will see that getting really small groups and really tight SD/ES isn't the most important use of your time. I found that video, here is the link.

Thank you very much for your effort and time, I'll check it out. I am comfortable out to 500yds with my old rifle scope set up. Most game shots in the area I hunt sre in the 2-5 yd range. This allows me to get in a stable position (prone over pack/log/ boulder ) or kneeling. The only unsupported shot at big game was a standing shot at an elk that obliged by coming in to my piss poor bugling to 35yds He thought I was a bush until it was too late . Ballistics were not critical in that situation.

 

[RegionRat]

If you intend to shoot at 600 or 1000yd you should tune at that distance.
A lot of the time it will not be the 200 yard load that would be best for the longer ranges.

Agree. Always best to test at the distance you plan to play.

But, folks who don't have their own long distance range don't need to give up either. You can get most of your work done with what you have, but then you need to put the right amount of weighting on where you spend your time and testing. You don't get away with very sloppy loading or SD/ES.

If we took someone who is constrained by 100 or 200 yards at their home range, but who intends to shoot 600 or 1000 the next weekend, then they should not only pay attention to the best results at 200 yards, but they should also show up ready to test the one with a good SD/ES that was still pretty good at 200 even if it wasn't the best.

Within limits, I will say more often then not, the best performance at 600 - 1000 isn't the load with the smallest ES/SD, but that said, it isn't sloppy either.

As the distance goes out past 300 yards, the root causes of vertical performance starts to shift from one bucket to a different one. Somewhere past 300 yards, but before 600 yards, a bad SD/ES will over-ride any good harmonics or tune.