I just got a chrony and tried it out this weekend.

To my great dismay, my hand weighed, carefully loaded match rounds showed an extreme spread of 137 fps, while my surplus Turkish 8mm showed only 37 fps. What is going on? Why is the mass produced stuff better than my 'hand crafted' loads?

Load workup is: (.223)
24.4 gr AA2230, Winchester small rifle primer (not match), Lake City 69 brass, on its third reload. The press is a Dillon 550b. temp was 65 F. The bullet was a Hornady 55gr Vmax and all of them were weighed and were exactly 55gr.

I hand weighed each of the charges on a Dillon electronic scale and accuracy is supposed to be .10 grains. I zeroed the scale after each charge. The charges were exact!

The only thing that I can think of is either the primers were inconsistant, or there are variations on the neck tension which cause a micro delay in the bullet leaving the case and thus raising the pressure.

I would sure appreciate some help.

My first guess would be your charge weight isn't optimized.

Contrary to conventional wisdom, there is a very specific amount of powder for a given application that ignites and burns more consistently than charges above and below that amount.

I refer to that as the OCW, or Optimal Charge Weight.

Here is a link that will explain my load development method, the reasons for going about load development in this manner, and even a few comments by shooters who tried the particular recipe profiled with good results--even though they were using rifles other than the rifle I used to develop the load ...

http://216.219.200.59/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic&f=13&t=000256

Of course you can make a precarious load recipe shoot well, but it will be very temperature and component sensitive. The better way to go is to locate the best powder charge for the application at hand, and then tune to your barrel's best harmonic node by altering bullet seating depth.

Naturally there could be chronograph reading issues (light conditions, etc.) that would also explain the disparity.

If the suspect load groups well at 600 yards, I wouldn't pay one iota of attention to what the chronograph said.

The truth is that in the end, each load must prove itself in the application. If it works, the numbers don't matter. And if it doesn't work, the numbers don't matter.

Right?

Best of luck,

Dan Newberry
green 788

Dan,
Thank you for the reply. Oddly enough, I had read your post on OCW and was trying to work up a load according to your instructions. I was just surprised that exactly weighed charges would vary.

Are you saying that in sub-optimized charge weights that the ignition and burn rate is inconsistant? That at an optimized charge weight, I will get a tight, repetitive burn window and outside of that charge I will get a greater amount of varriance, even though the charges are exact, shot to shot?

Thanks for your reply, and the other article I alluded to.
EV

I worked up a new load for one of my rifles when I first got my chrony, by loading a series of 5 cartridges each, in half grain increments of powder, from min to max per my manual. After shooting through the chrony, a trend emerged. My min load had a large ES and SD. As I worked up through progressivly hotter loads, the ES and SD shrank with each step, until I was 2/3 of the way to max load. Then the ES and SD got bigger and bigger as they approached max. The groups on my targets shrank and expanded exactly the same way. So now I tailor all my loads for small ES and SD numbers and only shoot one Max load out of the six rifle loads that I regularly use. I like the consistency and accuracy enough to give up a bit of velocity. I suspect that if you worked up a new load, the same trend may show up for you.

I'll never work up a load without a chrony again.

Elmo

"Are you saying that in sub-optimized charge weights that the ignition and burn rate is inconsistant? That at an optimized charge weight, I will get a tight, repetitive burn window and outside of that charge I will get a greater amount of varriance, even though the charges are exact, shot to shot?"

Yes, that's basically it. As Elmo mentions above, as you approach higher load densities (usually but not always commensurate with maximum charge) your numbers will look better.

Some of the Garand shooters who use IMR 4895 in lower densities used to (and may still) point the muzzle skyward before each long range shot, reason being to settle the low density charge of IMR 4895 against the primer for better and more consistent ignition. This normally equated to better groups.

Thanks for going with the OCW load method... Let us know what you discover, if you don't mind.

Dan Newberry
green 788

El Viejo,

Here are some targets from my .308 load development, done to ascertain the OCW of IMR 4895 with the 168 grain Sierra Matchking.

After I concluded that 43.6 grains was the OCW, I confirmed this by shooting a few groups at 300 yards. In each group was a low, mean, and high charge. In other words, a 43.3, 43.6, and 43.9 grain charged shot was in each three shot group.

One of the groups has two mean (43.6 grain) shots in it because the first shot struck in the black and I couldn't see it, so I shot an additional 43.6 grain shot, which not surprisingly came in right beside the one in the black.

Anyway, when the load is properly developed and assembled, it should perform very well indeed. For what it's worth, I don't use a chronograph for OCW load development. If properly read, the targets will tell you all you need to know...





Sorry about these image sizes, I didn't crop them enough...

The second target was shot in sporadic wind, and I was trying to catch the lulls. That group would have been tighter otherwise. The vertical deviation isn't much at all, though, which should attest to the integrity of the load recipe...

Dan Newberry
green 788

Two, three years ago I decided to retire my RCBS 1010 balance scale for an RCBS electronic. I had a heck of a time getting accuracy from a new 300 Win mag load I was trying to develop. This out of a very accurate rifle. After a few frustrating days of poor accuracy and variable velocity, I sat down and gave the situation a good think. I concluded that the only change I made of any signicigance was a swith to the electronic scale. I dug through my hunting box and came up with a few left over handloads from a hunting trip. I fired them and both velocity and accuracy were right on. I went back to loading, dug out my 1010, set it and used it to check the loads coming off the electronic scale. The variation was awesome. I resent the scale doing everything thing the manuel said to do. Same difference. I was loading in the house at a built in table that was solid and level. I went back to the 1010 and never had that problem again.

Most likely your 139 fps difference is due to the neck tension on your bullets caused in the difference of the neck thickness. If your case necks are off as much as .0100 to .0125 thickness would give you .0050 more case around your bullet which could cause the difference in velocity. Also it depends on the size of your chamber. Your could mic a fired cartridge and a sized cartridge to see how much brass you are moving between the two. Good luck

Reload is looking at the right thing, IMO. I'll go out on a limb and say that your "carefully crafted handloads" are seated out much futher than the factory stuff. And don't have a crimp.

There is a reason the old hands wanted a "one caliber" neck. It helps keep the velocity spread down.

Seat the two to the same length, and you'll see that the spread will be a lot closer. Switch to a milder primer, like a Rem 7 1/2 and the spread may just come down further, yet.

Third load might enter into it if you have a roomy neck. Annealing would both increase the neck tension, as well as make it more consistent.

Charge weight doesn't enter into velocity spread, for the most part, as long as the charge is consistent. HTH, Dutch.

Another funny thing that'll drive you bonkers is that ES variations don't mean much when measuring group size.

Anybody who's spent too much time crunching numbers will tell you that some of their most accurate loads have awful velocity spreads. Me included.

Where it IS critical is at extreme range where velocity inconsistencies will exhibit vertical stringing. Which is why I sometimes use a (slightly!) less accurate but more consistent load at long range. A round group always beats a vertical stripe down the target when scoring.

Redial

Dutch, help me with this one:

quote:

---

Charge weight doesn't enter into velocity spread, for the most part, as long as the charge is consistent

---

are you saying powder load does not effect velocity spread?

Harley, I don't mean to speak for Dutch, but I think what he means is that so long as the charge weight is the same for all the cartridges in a string of fire, the ES shouldn't be negatively affected.

My own view is that at certain powder volumes, inconsistent ignition does occur. And this will naturally lead to sporadic velocities. I think that's pretty much why we see a load do poorly on target: The bullets are exiting the muzzle at various points on the harmonic whip, and therefore don't group well.

When you have a truly consistent powder charge (like Federal's 43.5 grain charge of IMR 4064 in their 168 grain Match loads), the load will shoot very well in the majority of rifles chambered for that cartridge.

I will admit that case neck variations could be the cause of the velocity spread that El Viejo is experiencing. Since he seems to have meticulously prepared everything, I thought that charge weight consistency would be the first potential culprit. Lake City brass is some of the very best out there, and so long as it is from the same lot, and on the same firing, I wouldn't expect this to be a neck tension issue.

I could be wrong, though.

Let's see what he finds out...

Dan Newberry
green 788

Dan,

Thanks for the reply - that makes sense to me. Enjoy your postings - who are obviously quite knowledge and clearly articulate your reasoning. It is educational. Curious to me more postings did not bring up the chronograph variable - especially if this was the first time he used one. That can be a tricky experience.

Thanks for your time - love to learn!

Harley,

Regarding the "chronograph variable", are you suggesting that the chrony might have some slop on the repeatablity, giving, what is essentially, bad data?. Since this is my first chrony, there are probably a lot of things I don't know about it.
BTW, the machine is a Dillon Millenium Chronograph.

Dan,
I will report back, but the range is only open on the first weekend of the month, so it won't be till Feb.

El Viejo,
The chronograph set up is very important to consistent readings. I think others have posted on this better than I could. While readings significantly off are easy to recognize and remove from the string its the minor inconsistany that impact the stats and ,ay mislead the reloader. Many manufactures will address some options in set up, distance from crown, ideal path through sky screens, lighting etc. (I am not real familiar with Dillon). Some will have suggestions on thier web sites some in manuals. Some may argue the variances are irrelevant - it depends on your objective. But with the optimum set up for each chrono I have seen much more consistent readings and the same machines reading match grade loads vary more than acceptable to me. Hope this helps

[ 01-13-2003, 06:12: Message edited by: Harley ]

Thanks

Dan, thanks for the assist. That is, exactly, what I was trying to say.

Certain combinations of case volume, neck tension, powder and primer do seem to have problems igniting consistently.

When you get a combination that you ARE able to "tune" using the Audette/ladder/OCW methods, then, in my opinion, the cartridge system works. A few grains of powder up or down really can't make or brake an ignition.

If your gun won't shoot a combination of powder/bullet/primer at any speed, there is a problem. Either you are completely outside the harmonics windows where the barrel whip slows down, or your bullet starts moving randomly. Light neck tension and violent primers are one of the prime suspects in those situations.

There was an article in Precision shooting in '97 that listed primers in order of how far they moved a bullet into the barrel. Some primers moved the bullet on average nearly 5" on their own power. The interesting part was that the range of movement was from 2 to 6 inches on some...... Adequate neck tension (or seating jammed into the rifling) can overcome a good bit of such primer variability. HTH, Dutch.

Dutch

If I understand the logic and physics then tight necked guns should not be impacted by primer inconsistancies?

Shoot straight.

Let's put a different "spin" on this for a second. My ideas may or may not apply here, but let's look at the beginning of loading these shells.The numbers are only for example reasons. If a case weighs 219.7 grns. and another 225.8 grns., they will have two(2) different case capacities. Heavy cases have less internal volume. Light cases may have too much volume. Now, if this is true, and if air space affects powder shifting, changes in ignition, pressure, and velocity; and if cases with unequal volumes develop uneven pressures (even w/ carefully weighed powder charges) then are we dealing with a varying case capacity situation?
I cannot say I've encountered the situation of velocity spreads like you have, but my theory may explain why it doesn't show in factory loadings. Different headstamps are all you need to throw case weights out of whack! If I am too far off kilter, someone let me know, or maybe I'm thinking to simple - just thought a fresh angle would help.

Harley, no, tight neck really has nothing to do with neck tension. There is still room around the neck for the brass to expand into and release the bullet.

Tight necks DO align the bullet better with the bore (if the chamber is concentric with the bore, of course). It should not affect neck tension. If the brass touches the neck, and all brass is not turned to the exact same dimension, variability would INCREASE, not decrease. The extreme of that variation being a gun that blows up, like perhaps Todd's did. JMO, Dutch.