Wink ----- I was out of town when I read your reply and couldn't wait to get my records from my shooting logs and start the debate. However at close inspection I discover that my SD is not Standard Deviation, but Sum of Differences, which are entirely different animals. Sorry for the confusion. ----- When I looked at my logs it proved in my mind exactly what I said. I use the Chrony Test Record typical sheet that I first started using when I got my first Beta model Chrony, which I wore out then got a Gamma model, wore it out and eventually went to a Oehler Model 35-P. Still using the sheet for the Chrony for all my recordings. I found a typical log of one of my .358 STA rifles, with a 225 grain North Fork bullet, 1st shot = 3061, 2nd shot = 3061, 3rd shot = 3062 for a Sum of the Difference of O. Ah Ha I said, there it is, then I noticed my SD was not Standard Deviation, and said "Oh Shit", we are talking about two different things altogether. In my mind I was right, but in actuality I was wrong in what the debate was about. Thanks for clearing up the matter. I pride myself for keeping all the records and always wonder why I go to the trouble (it is the part I really hate), but in the end it will pay off when I shoot that one hole group with the big boomers, after all the shooting and Chrony work. By the way, I met you in Dallas a couple of years ago, I was the nut in the Black Cowboy Hat with the Elk Ivory hatband. Good shooting.

Has anyone found that heavier bullets (higher sectional density) are easier to get more consistent velocities with? Just curious. I was thinking that the higher the sectional density, the less sensitive the load might be to case neck grip - and the slower acceleration might result in more consistent burn?

303Guy

With the number of different powders, and types of powders available tody that may be a tough one to nail down.

I'll say this from my experience is that most powders have a certain range of pressure where they begin to burn efficiently. Thus they generally get into that pressure range sooner with a heavier bullet.

I've not observed that heavier bullets give more consistant velocities than other bullets when appropriate powders were used but then I've not specifically looked for that. I have observed that really light for caliber bullets can have serious consistancy problems with medium and slow powders in most cartridges.

When using medium and slow burning powders with cast bullets the heavier bullets will get the pressure into the range of consistant burning while maintaining an appropriate velocity/RPM for accuracy where a medium or light cast bullet will not.

Probably not much help as these are just my observations. I suppose a test could readily be done but I'm wrapped up in other tests right now.

Larry Gibson

quote:

Originally posted by 303Guy:
Has anyone found that heavier bullets (higher sectional density) are easier to get more consistent velocities with? ...

No. SD has nothing at all to do with consistent velocities.

quote:

Originally posted by 303Guy:
Has anyone found that heavier bullets (higher sectional density) are easier to get more consistent velocities with? Just curious. I was thinking that the higher the sectional density, the less sensitive the load might be to case neck grip - and the slower acceleration might result in more consistent burn?

It could act like the mass damper that Formula 1 outlawed last year in ameliorating the influence of other effects. Very interesting.
.

Thanks for that folks! Ummm... I'm gonna hafta look up that word, amelio-something!

quote:

... these are just my observations ...

That answers my question exactly - thanks, Larry.

quote:

Originally posted by phurley5:
Wink ----- By the way, I met you in Dallas a couple of years ago, I was the nut in the Black Cowboy Hat with the Elk Ivory hatband.

Pat, I remember you very well and a good time was had by all that year in Dallas. I just hope I can make it to another, and if we have time to throw back a few I'm sure we'll get SD's down into the negative numbers.

When using small samples (5-20 shots), I consider the extreme spread more important than the SD.

quote:

Originally posted by Hot Core:

quote:

Originally posted by 303Guy:
Has anyone found that heavier bullets (higher sectional density) are easier to get more consistent velocities with? ...

No. SD has nothing at all to do with consistent velocities.

I should have been more specific here.

Sectional Density has nothing to do with consistent Velocities. With all the Powders we have available today, it should be relatively easy to find a Powder that gives Relatively Consistent Velocities with ANY Bullet weight.

Standard Deviation in relation to Velocities does indicate the amount of Variance in the Velocities in a given string of shots.

Oh I wish I had been in on this topic much much earlier !!.

stillbeeman
one of us

Posted 06 May 2008 17:32 Hide Post
Folks, isn't this kinda akin to the folks that do a labour intensive case prep BEFORE they ever shoot and fire form the cases?
I mean, you are ultimately looking for bullets that go thru the same hole. If you acchieve that, then the ES and SD become moot. And pretty well take care of themselves. I've never heard of a stool shooteer yet that shot a 3" group and said "yeah, but I've got my SD down to 3fps".
I think all of this got started by some rag writer as a Phillip Space thing. And, of course, before every kid on the block had a Chrony, it wasn't heard of and they did some pretty good shooting back then. Now things have changed and it's something for the gadget heads to measure. Why? Because we can.

SeaFire also posted a profound statement !.

one would think that the load with the lowest SD spread would be the most accurate....

Sometimes it is, and sometimes it isn't ...


I will only add this ; MOST TIMES IT'S NOT !.

My shooting partners and I have compiled K's of targets with crony's over the years for so many different cartridges it's pathetic . We were obsessed what can I tell you . Had to get Perfect Numbers had to !!. NEVER HAPPENED !.

The most consistent groupings for any of our M1 's have an average of 85 FPS deviation .

The very worst grouping had 7 FPS deviation !.

These figures were for groups of 5 at 100 Yd.

I was Mortified and would have hoisted the BS flag 20 times over on my self , if only I had been doing this testing !. 4 Shooters all doing the same testing using 4 different M1's and 3 different chrony's two different brands .

We even tested the chrony's against themselves !. 15 shots of identical loads through each crony produced a Std. Deviation of 2 averaged !.

So what does it all mean ?. Load for accuracy and forget the numbers or you'll end up in an asylum !.

Shoot Straight Know Your Target . ...

quote:

Originally posted by Remington720:
When using small samples (5-20 shots), I consider the extreme spread more important than the SD.

Excellent post and most valuable information. SDs mean little until you begin to shoot multiple groups of 10 shot strings with the same load. A 20 shot string will provide some reliability to SD figures but 5 shot groups do not. With small samples of 5 shot groups the ES is indeed the most important figure.

To quote Dr. K; "These figures were for groups of 5 at 100 Yd.". It is no wonder he was "Mortified" with his use of SD using only 5 shot groups. It is unfortunate that most users of chronographs have become enamored with the SD figure, mostly from the writings in the gun rags.

In reality if using 5 shot strings or only using one 10 shot sample use the ES. It is much more reliable. As always additional strings should be fired to confirm or deny that loads repeatability and consistancy. It is a fact, give quality bullets and an accurate rifle, that the more consistant a load is in ES the more accurate it will be, espially at long range.

Larry Gibson

Dr. K, Excellent post. Just goes to show the larry is WRONG as usual and that the people who worship the Numbers are missing the point.

quote:

Originally posted by Hot Core:
Dr. K, Excellent post. Just goes to show the larry is WRONG as usual and that the people who worship the Numbers are missing the point.

Hot Core

Were you born stupid or did you go to school for it?

This is what I said; "most users of chronographs have become enamored with the SD figure, mostly from the writings in the gun rags." Anyone can see that is hardly worshiping the numbers.

Dr. K would be far better served not taking the size of just one test sampling as fact. That is what you do. Instead of just going by group size at 100 yards he would be far better served to take the loads that showed the best consistancy using the ES and then loading a 20 shot string of them and testing that. Then he should take the the best one or two of those and shoot 20 shot strings at a minimum of 300 yards. That would then tell him which load is actually the most accurate in his M1 rifle.

The real point is, which it is you that have been missing that point, is; you have been told many, many times by those of us who know how to use a chronograph that the numbers only guide you to the most accurate loads. They do not tell you the most accurate loads.

Once again more BS and lies from you.

Larry Gibson

Personally, I think both Larry Gibson and Hot Core are libraries of knowledge and infomation and I enjoy the shared experiences posted by both of them! I wish I could meet these two folks someday. But I am in a different part of the world altogether.

quote:

Originally posted by 303Guy:
Personally, I think both Larry Gibson and Hot Core are libraries of knowledge

Hey 303Guy, You got that 1/2 correct

quote:

I enjoy the shared experiences posted by both of them!

If it wasn't for Trash Talking, larry wouldn't have any "Experience" posts at all.

quote:

I wish I could meet these two folks someday. But I am in a different part of the world altogether.

If you can fly in to Louisville this weekend, we can go to the NRA Convention, do some shooting, eat some BBQ, maybe do a bit of fishing and even toss down a Blue Ribbon or two if you desire. And we can read some of larry's posts if we want to

If you want to take a stab at predicting where your chronied loads will go, hit www.handloads.com/calc/ and see an estimated trajectory for the velocities your chrony gives you. Great fun!!

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