While attempting to work up a load for my 6.5-06, I am booking some pretty wide variations in my velocities. Using 50 grns of 4831, I recorded a low of 2633 and a high of 2681. My average was 2651 with 4 shots. The temp was a round 36f.

Same powder lot, same case lot, same primer lot, SMKs sorted by weight, cases trimmed, charges weighed, everyhting as consistent as I know how.

#1 Is this powder more sensitive to colder temps than other powders?

#2 What else might cause a deviation this wide? This is pretty wide, right?

Any comments appreciated. jim r

I don't think only 4 shots is a fair test of consistancy. However, an extreme spread of less than 50fps is not egregious. Clean your barrel, shoot some more, then come back.

Point taken on the number of shots. That is exactly why I posted it. Thanks, and I will do just what you suggested. Jim R

Jim R. - Take two aspirin and call me tomorrow. Seriously you are worrying about how many angels can dance on the head of a pin IMHO.

Chronographs are fun to play with but I think their main function is to give their owners worrying about things that don't amount to a hoot in hell.

I'm not trying to flame you at all...I just honestly think you have an issue here. Certainly not one I would give a second thought.

Good hunting. P45

I do not doubt what you are saying, Pecos45. Since getting AcculoadII, I have been a bit anal about my data. This is my first load from scratch in my first custom rifle, so the details are getting scrutinized pretty thoroughly.

My only hangup on the velocity variation is that since I have had this reloading disease, I have never experienced a deviation of more than 25 fps on any of the loads I have kept velocities on. For some reason, that figure almost doubled.

My goal is to venture into the LRH arena and to do so, i am just keeping things as tightly controlled as possible. I take your point in good spirit, and appreciate your reply. Thanks again, Jim R

Jim,

The temperature stability would depend on which 4831 you're using. IMR 4831 won't be as stable in varying temperatures as H4831 "extreme" by Hodgdon.

But I completely agree with Pecos45 when he says:

"Chronographs are fun to play with but I think their main function is to get their owners worrying about things that don't amount to a hoot in hell."

It's my opinion that chrongraphs are fine for a quick check of approximate velocity, but even there they aren't totally necessary. This is an unpopular opinion, I know, but the truth is that no matter how good or bad the numbers look, the ultimate test of a load recipe is either the dead animal or the cluster of shots on a target.

I developed a .308 win target load using my optimal charge weight load development method. The load uses 43.6 grains of IMR 4895 behind Sierra's 168 grain Matchking. This load will put three shots into a 1/2 MOA (1.5") group at 300 yards with one shot .3 grains low on the charge (43.3), and one shot normal (43.6), and one shot high (43.9). The velocity spread of this three shot group would probably not be impressive, but the target certainly is. The above tests results in sub MOA at 600 yards for three shots also.

At extreme range, the charge variations would be more of an issue, but may yet be at or near MOA. If I individually weigh each charge to the 43.6 grain weight, I have supreme confidence in the load, and any aberrations on the target are mine.

And the point is I don't really care how fast this load goes (I know that it goes ~2700 fps from my rifle but that's beside the point). The load performs!

Anyway, best of luck with your load development... I've heard that the 6.5-06 is a booger to load for, but having no experience with it I can't offer much beyond best wishes...

Dan Newberry
green 788

Jim, what primer are you using?
You can bring that high spread down, like you say, under 25 with either a different primer, different charge wt or adjusting OAL and if that doesn't do it a powder change might be the only option left.

The cronograph can tell you where a stable or flat spot in velocity can be found in load development and a lot more too. Here's something you might find helpfull. Hope you can see it to read it.

FWIW, I generally find commercial ammo to have about a 35 fps standard deviation on velocity, give or take. My handloads are generally more consistent than that... usually in the low 20's on "fussy" calibers, and single digits on some of the less fussy ones.

Making the usual assumptions, about 68% of cases will be found within plus or minus 1 standard deviation of the mean, and 95% within two.

I haven't run the math on four shot groups, but with five, you can expect about a 3:1 ratio between the upper and lower confidence interval on standard deviation. In other words, a 10 fps standard deviation (95% within plus or minus 20 fps) and a 30 fps standard deviation (95% within plus or minus 60 fps) are pretty much statistically indistinguishable with groups of five. So four is far too few shots to establish an estimate of "spread", whether you're measuring that with range ("extreme spread") or with standard deviation.

Ok. The powder used was H4831. Primers are CCI 200 Large. Sorry for leaving that off.

I went back to the range today and here is what I found.

The only change I made to the load was OAL and it certainly made a difference not only on deviation but in average velocities as well.

Just touching the lands in this rifle is an OAL of 3.350 using SMKs. Here are my velocities today, not including my first fouling shots before each group:
OAL-3.350
2722
2775
2757
2784
Average 2759

OAL-3.345
2769
2780
2763
2759
Average 2767

Remember, yesterday, the same load with OAL of 3.325 averaged 2651. High of 2681-low of 2633.

Today, same load, 10 degrees warmer, different OAL, and almost 100 fps difference.

Accuracy? The 3.350 OAL was .991 for a 4 shot group, the 3.345 was .541, and yesterday at 3.325 was .704.

Can you tell I'm having fun yet?

Jim R

[ 12-16-2002, 05:23: Message edited by: Jim R ]

Jim R - Yes, your results are interesting and I'm glad you're having this opportunity to experiment with it. You'll learn a lot if you pursue it.

I guess I'm repenting here publically for all the times I've sighed and rolled my eyes when I see guys talking about their Chrony's and velocity this and velocity that.

Like I said, I had one once upon a time and fiddled with it for awhile. I learned 3 very important things from chronographs.
1. You can change one little thing with a load and things can go all over the scope. There's a zillion variables and it can get like a dog chasing his tail if you aren't careful.
2. I didn't have the patience to mess with it all. I grew up and lived the early part of my life in the wilds of New Mexico which was a "target rich" environment and free hunting land where a guy and his rifle could go out and do whatever he thought he was big enough to try.
I would always rather be out hunting and shooting at things than on the range with my chronograph and notepad.
3. Considering my flavor of hunting/shooting, the chronograph wasn't going to teach me anything that would really do me a lick of good.

So I sold the thing and stopped worrying about it. If my load shot good in the field and did what I expected, that was all I cared about.

But all this said, MY ideas on the subject don't mean nothing. You guys that have them and like to work with them...go for it. Don't let a cantankerous old fart like me pour water on you.

Now I'm gonna show myself out of this thread and go pester someone else.

PS - You fellows might find the thread "Does Velocity Rule" interesting. I think it's up on Big Game Hunting.

I actually agree with most of what Pecos said on the subject, even though my interests are more in the physics and statistics of good loading... I really need to spend more time out in the sagebrush, but that's another story.

Consistency in loading and muzzle velocity does improve accuracy, but any carefully done handload in a good rifle will be more accurate than almost any of us. So Pecos is right: Trying for a super tiny spread on muzzle velocity isn't a high payout activity in most cases.

However, there is one thing about your experiment that worries me: If you load so your bullets touch the rifling, your maximum load is ordinarily reduced a grain or two. Bullets touching the rifling sometimes helps accuracy, but usually does increase pressure.

There's nothing wrong with an old fart every now and again. Truth is, old farts are probably good and healthy for the system I appreciate your candor, and insight as well.

I might be posting a lot of this just to confirm some of my data, cuz obviously, I am somewhat new to this obsession of "rolling your own", at least from a benchrest standpoint. Thanks for your patience to all who have replied.

That one of my OALs is touching the rifling has not escaped my attention. Based upon what I have learned over the last year or so in the process of having my first "hot rod" rifle built and preparing to work up a load from scratch for it, I ascertained that this caliber combo does like bullets close if not touching. I have worked up to that point carefully and realize I am at the published limits of this particular powder.

I do feel as though I can achieve a bit more velocity, although that is not the ultimate goal. Accuracy and percision is. I have no doubt that this rifle is capable of sub MOA for a five shot group. But it is going to take me awhile to find it. Until then, i may drive some people nuts in the meantime......

One thing about this load and powder that I do not like is that I am approaching the end of the spectrum in regards to using the H4831(I still have about 6lbs left and only use it for one other rifle that is not near as fun to shoot). Case capacity is only in the neighborhood of 80%, and I am a firm beleiver that a full case is best.

Thanks again for the comments. Jim R

I guess there's a little of the benchrest shooters blood somewhere in me even though I do much better in the field than at the bench.

I do get some satisfaction from getting a rifle to do it's best, so as long as it still teaches me more I guess I'll be traveling that road.

Sounds like you have good velocity and seems the spread may be getting tighter too, and all that with good groups

I'll bet you will see more consistancy in velocity if you increase your powder charge. I have noticed, especially with slow burning powders, that loaded density has an effect on velocity consistancy.
My own work with the 6.5-06 has shown a max load around 54.0 grains with H4831 and the Sierra 140 MK. I would be more interested in what your velocity deviation is as your powder level increases. My best loads were with RL 22 and near max loads. Let us know what you come up with.
John

Just a few thoughts.

1. Your first test at 36 degrees was getting down to the temp where chronographs don't work and some of your results "might" be attributed to that.....it's doubtful is a few degrees increase in temps would give that kind of increase.

2. You don't say what chronograph you used but some are more sensitive to where your shots are going thru the screen...especially height.
Read your manual closely and put some colored tape on the supporting rods to show optimal height about the sensors...makes an easy reference and allows you to be a bit more precise.

The chronograph was a ProChrony. I hadn't thought about the temp issue. This unit, while cheap it may be, has always compared closely with some of the more expensive ones I see at the range. We have shot thru each others chronys just to see what differences we booked and they were slight to none.

In regards to the height at which i am shooting thru, I will have to look and see what the directions say. Truthfully, all I have tried to do is be consistent with the height. I will look that up and see what it says. Thansk for the heads up, Jim R