Extreme Spread chat

[TommyD11730]

Like the title says, chat about extreme spread. What do you as a reloader think is the biggest contributor to big ES?
Oh and do you believe some calibers are prone to large or small ES?

Thanks Guys!

 

[Benchrest Braxton]

biggest contributor to big ES is incorrect powder burn rate. Primer choice. Case capavity variation. Powder charge variation. Neck tension. In that order. Then bunch of smaller factors.

Yes, small case capacity/small caliber cartridges are much more prone to big ES.

 

[Krogen]

I recently learned about light powder charges in Bullseye pistol handloads. We're total weenies and like to load our .45 ACP rounds light. My load of Vihtavouri N310 under a 185 gr Nosler bullet yielded an extreme velocity spread exceeding 200 fps. (Thank you Garmin!) For an average velocity of 700 fps (I did say light didn't I . . .) that's HUGE. Bumping up the charge tightened up the extreme velocity spread. I can only imagine it was inconsistent powder burning at low pressures leading up to the high extreme spread. The fix didn't help my scores, but that's a horse of a different applecart. (so to speak. . . .)

 

[Straightshooter1]

Like the title says, chat about extreme spread. What do you as a reloader think is the biggest contributor to big ES?
Oh and do you believe some calibers are prone to large or small ES?

Thanks Guys!

I don't really focus on ES's because it's only a measure of two data points for any set of data points. So. . . for the most part, when it comes to MV's, I prefer to focus on SD's to tell me how well I'm reloading. If I continually get an outlier for a given set, which of course, will produce a big ES and have some effect on the SD, I'll try and find out what's going on.

In terms of what's on target, I like to focus on Mean Radius and get that number as small as I can. A single "flyer" in a set that produces a bad ES doesn't really tell me anything, unless it's recurring. Then I'll analyze the shooter (like me) to see if there's something about my shooting mechanics and/or wind read is off. . .or try to find if there's something involved with my reloading process that's given me unacceptable ES's (flyers) on target.

 

[TommyD11730]

That's some good stuff.. good replys for sure, thank you.
So.. on a smallish caliber, say 223 would a ES of 50 be considered "big"? That seems to be about my avg with my SD 15 or less (in a 50 shot string).
I guess I'm jealous of the ES I see in larger calibers.

 

[mgunderson]

That's some good stuff.. good replys for sure, thank you.
So.. on a smallish caliber, say 223 would a ES of 50 be considered "big"? That seems to be about my avg with my SD 15 or less (in a 50 shot string).
I guess I'm jealous of the ES I see in larger calibers.

Is this a 223 with heavy bullets? That is a different animal than a 6mmbr with 105s.

An SD of 10 to 15 in a 223 with heavy bullets and a bolt gun is very competitive. It is important on how you are measuring that too.

 

[RegionRat]

So.. on a smallish caliber, say 223 would a ES of 50 be considered "big"? That seems to be about my avg with my SD 15 or less (in a 50 shot string).

Well, let's just say that sounds close to typical.

It does take some work and focus to get a 223/556 velocity stat to go down under an SD of 15.
For whatever reason, 223 is a difficult one to get under control.

BTW, It is a little strange that with 50 shots, if your SD was roughly 15 your ES would typically have been from 60 to 90 (4x to 6x sigma). By getting only ES of 50 after 50 shots, you were doing good. Getting that ES under 30 for a long string in 223 is considered high class.

 

[boltfluter]

Short and fat is where it's at! For cartridges that is, and not for women. Any 6BR or variant will be easier to get low extreme spreads on compared to a .223 cartridge. Annoying, as I am a fan of both cartridges. Interesting post, carry on.
Paul

 

[Doom]

That's some good stuff.. good replys for sure, thank you.
So.. on a smallish caliber, say 223 would a ES of 50 be considered "big"? That seems to be about my avg with my SD 15 or less (in a 50 shot string).
I guess I'm jealous of the ES I see in larger calibers.

If you have a 15 SD in a 50 shot string you are doing extremely well. You would expect to see a ES north of 4xSD up to about 6xSD for an ES. That's 60 to 90 fps.

 

[10XSHOOTER]

What about the new 22 ARC? it's short and fat. Should it produce low ES and SD's
I'm thinking of building one

 

[Krogen]

Many of us like to talk about Standard Deviation (SD). It's a figure of merit, all right, but it's not that meaningful with a small number of shots. I guess we talk about it because our chronographs provide it. That doesn't mean it's necessarily useful.

Depending on who's talking, SD is only statistically meaningful with a population of 30 or more. SD is a relatively complex calculation. It's not easy to get an intuitive feel for it. Extreme spread (ES) is just that. It's basic arithmetic. SD can fool you if you try to compare groups with different numbers of shots. Using SD to judge the uniformity of velocity in a 3-shot vs. a 10-shot group doesn't work.

 

[TommyD11730]

Is this a 223 with heavy bullets? That is a different animal than a 6mmbr with 105s.

An SD of 10 to 15 in a 223 with heavy bullets and a bolt gun is very competitive. It is important on how you are measuring that too.

80.5 FB.
Now that I have a Garmin I'm using it every time out. When I was using a Magnetospeed.. not nearly as much.

 

[TommyD11730]

Short and fat is where it's at! For cartridges that is, and not for women. Any 6BR or variant will be easier to get low extreme spreads on compared to a .223 cartridge. Annoying, as I am a fan of both cartridges. Interesting post, carry on.
Paul

I'm new to the 6br. I watch the numbers my friends rig puts up and just blink in disbelief.

 

[TommyD11730]

Short and fat is where it's at! For cartridges that is, and not for women. Any 6BR or variant will be easier to get low extreme spreads on compared to a .223 cartridge. Annoying, as I am a fan of both cartridges. Interesting post, carry on.
Paul

LOL my 1st wife I used to say was on the short/fat pill.








When she wasn't within earshot that is.

 

[hoz53]

Short and fat is where it's at! For cartridges that is, and not for women. Any 6BR or variant will be easier to get low extreme spreads on compared to a .223 cartridge. Annoying, as I am a fan of both cartridges. Interesting post, carry on.
Paul

Short and fat is where it's at! For cartridges that is, and not for women. Any 6BR or variant will be easier to get low extreme spreads on compared to a .223 cartridge. Annoying, as I am a fan of both cartridges. Interesting post, carry on.
Paul

I think thats true- i want to chamber this 6.5 barrel ive got to 6.5/06 but im thinking a 6.5 pcr would give me a chance at better accuracy

 

[Straightshooter1]

Many of us like to talk about Standard Deviation (SD). It's a figure of merit, all right, but it's not that meaningful with a small number of shots. I guess we talk about it because our chronographs provide it. That doesn't mean it's necessarily useful.

Depending on who's talking, SD is only statistically meaningful with a population of 30 or more. SD is a relatively complex calculation. It's not easy to get an intuitive feel for it. Extreme spread (ES) is just that. It's basic arithmetic. SD can fool you if you try to compare groups with different numbers of shots. Using SD to judge the uniformity of velocity in a 3-shot vs. a 10-shot group doesn't work.

For the most part, I agree. . .as the larger the population the more SD has more a accurate meaning. As small as 5 shots are for any "meaningful" SD, it still can be useful. For example, when I started precision reloading, my 5-10 shot SD's were generally in the mid teens to mid 20's (this being for a .308). My goal was to get consistently into the single digits. After a while, with improved brass prep, I was consistently seeing mid teens, with ES's kinds all over the place. Then with a new FX scale, my SD's plunged into the single digits, where it's quite consistently there and the ES's followed, being lower and more consistent and in line with what one might expect for any of the SD's. My SD trend improved and while they were mostly 5 shot SD's, I find the trend meaningful.

Though I don't like to focus on ES measurements, being just a measurement of 2 shots), I do find ES's are basically helpful during load development. Like where I might shoot a number of 3 or 5 shot groups to get a good read on what the loads are doing. If only the first 2 shots of a group produce a large ES, I'll not shoot another since anything following wouldn't really improve the result and tell me anything more than I want than those two did.

Since I like to focus on consistency, SD's tell me what I really want to know. ES's are helpful, though in a different way.

 

[RabbitSlayer]

99% of people tell you the es and sd of 5 or 10 shots. When you start shooting strings of 20 or 25 their magic numbers are likely closer to yours than you think. Watch the Hornady podcast about sample size. Im now shooting 3 or 5 shot groups to narrow it down, but before I call it good im shooting 20 or 25. So far, like they say the differences between loads really decreases when you have a larger sample. For me, brass made the biggest difference so far. A creedmore scale and weighing +\- .01 gr cut in half for 17 hornet. It did very little for 6 creed. Haven't tried 223 yet. I suspect it will cut it more than it did for 6 creed.

 

[Straightshooter1]

99% of people tell you the es and sd of 5 or 10 shots. When you start shooting strings of 20 or 25 their magic numbers are likely closer to yours than you think. Watch the Hornady podcast about sample size. Im now shooting 3 or 5 shot groups to narrow it down, but before I call it good im shooting 20 or 25. So far, like they say the differences between loads really decreases when you have a larger sample. For me, brass made the biggest difference so far. A creedmore scale and weighing +\- .01 gr cut in half for 17 hornet. It did very little for 6 creed. Haven't tried 223 yet. I suspect it will cut it more than it did for 6 creed.

Likewise, I don't "call it good" until I get a long string that corroborates what I think I've got. For example:

Last October I ran 50 rounds through my 6.5 PRC and got an SD of 9.4 with and ES of 36 with my MagnetoSpeed. Then a month ago I ran another 50 rounds of the same load and got an SD 7.4 with an ES of 26 using my new Garmin chrono. The Garmin making it a lot easier and me more willing to chrono long strings.

Also, last month, I ran 50 round through my .308 using my Garmin and got an SD of 5.4 with and ES of 23.

From what's been stated about where my ES's should be mathematically for those SD's, I'm pretty very surprised at those numbers.

 

[memilanuk]

From what's been stated about where my ES's should be mathematically for those SD's, I'm pretty very surprised at those numbers.

How so?

They all look like you're right around +/- 2SD, or the 95% level. Probably going to take more rounds than that - or an off day - to actually show all the way out to +/- 3SD / 99.7%.

How sure do you really want to be?

 

[Straightshooter1]

How so?

I was just expecting the ES's for those 2 SD's to be more like in the 40's to low 50's. . . upper 30's at best for 50 shots. At the time, that was just my guess as I don't know the math.

They all look like you're right around +/- 2SD, or the 95% level. Probably going to take more rounds than that - or an off day - to actually show all the way out to +/- 3SD / 99.7%.

How sure do you really want to be?

As a perfectionist, I'd like 100%. But I realize that's not realistic, though 98% would make me feel real good.