trickled vs. thrown - data?

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Lake City settled for a Winchester ball powder that metered to half the weight spread that Remington's extruded powder had in M118 Match ammo whey they operated the arsenal. Winchester's stuff shot worse than Remington's did.

While Winchester's ammo still met arsenal specs of 3.5" mean radius at 600 yards, it never got close to 2" like Remington produced M118 ammo often did. Military rifle teams hoarded all the Remington made stuff as scores shot with that of Winchester was not worth writing home about.
 
Bart B. said:
Lost Sheep's comment: 3/10ths grain spread for an average charge weight of 45.3 grains of IMR4895. A lot of info on powder measures accuracy and use is on the 6mmbr web site; www.6mmbr.com.
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Thanks for the link. I will have to read that later (I am at work taking time during my lunch break right now).
Bart B. said:
Your reference to a powder's pressure/temperature band is the first time I've ever heard of such a thing. I don't think any powder company list it in their load data, do they? I don't think its something that most people know about, use, nor understand or even heard of; it ain't axiomatic to me.
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I apologize if I came across as snarky. The idea that powder works best within a particular pressure/temperature range came to me from various discussions of performance and my observation of how quickly powder burns at 14.7 psi vs 14,000 psi and higher.

I have personally observed that smokeless powder burns rather slowly at normal atmospheric pressure (around 14.7 psi), but much more quickly (inside a cartridge, for instance) at higher pressures. I understand also that the release of the oxygen tied up in the nitrates in the propellant is faster at higher temperature and pressure than at lower temperature and pressure, contributing to a quicker burn. Also, anecdotes of incomplete combustion of propellants when charges are reduced implies that pressure has something to do with performance, that performance at low pressure can be erratic.

All this leads me to the belief that (like many other chemical reactions) the speed of the reaction depends on environmental factors inside the cartridge. Pressure and temperature are the most obvious to me.

Essentially, the same idea that requires a narrow range of fuel to air ratio in an internal combustion engine before you get efficient power.
Bart B. said:
So, to reference your penchant for providing links, provide one that clearly explains a powder's pressure/temperature band as well as a table listing powders' numbers for that. I'd like to know what it's all about.
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Sorry, I don't have one. If I find one or more, I will post. What I posted above is all I have right now except for a post (I think it was from UncleNick) who referenced the speed of oxygen release being dependent on temperature. But I did not save a link. Sorry about that.

I have never seen a table such as you describe. I expect that may be because the powder makers know that most loaders do not have the equipment or knowledge to make use of that raw data (the temperature probe you mention, for instance).
Bart B. said:
And also a link to some place where reloaders can buy a temperature probe to measure their powder burn temperature to ensure it's within specs. Reloaders can buy piezo strain gauge systems to measure their loads' pressures.
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As I said before, I did not mean to criticize your post, only to ask you to provide some direction to those who want to research further. You are obviously expert in the practical matters of shooting accurately and loading quality ammo, and I respect that. The theoretical aspects of the shooting sports (internal ballistics, mostly) is a bit more esoteric than most of us want to pursue, but any boost from your knowledge base in that regard would be helpful to some who want to do that.

Lost Sheep
 
Sierra Bullets has been metering charges into their unprepped, full length sized cases testing their bullet for accuracy since the 1950's. Weighing charges to zero spread didn’t show any better results than metered ones with a couple tenths or more grain spread in their test ranges. They tested at 100 yards in their California plant but switched to 200 yards in their current plant in Missouri. They use rail guns so all human and rifle variables are removed; they’re just testing bullets to get best accuracy with them

Their 30 caliber match bullets up through 180 grains are shot from .308 Win cases. Heavier ones 190 to 240 grains are now shot from .300 Win Mag cases. 10-shot groups are fired periodically during production runs. They all shoot under ½ MOA averaging 1/4 to 1/3 MOA. Some are smaller down in the 1/8 MOA range. I’ve seen 10-shot groups with 168's and 190's shot from .308's in their California plant all about 1/10 MOA.

Benchrest rifles shot for several 5- or 10-shot groups in aggregates are measured as the average groups size of all groups fired. The record ones through 300 yards are about .300 MOA average which means their largest groups are around ½ MOA or bigger. Some of the aggregate records are around ½ MOA; largest group over 6/10ths MOA.
 
When I was shooting Benchrest we all threw our charges, and many had no idea of the weight, just how many "clicks" they were using.

It made no difference at 100 and 200 yards. If it did, everyone would weigh charges.

The best are always at the top of the leader board because they are the best shooters, not because they weigh charges, or because their gun/load combo is better than everyone else's.

The differences in shooter skill in gun handling and wind reading is far far greater than the tiny differences between 90% of the guns and loads on the line.

The big dogs are the big dogs for a reason, they are the best. They can be beaten, but not often. When it comes to grand aggregates, the cream always rises to the top.

I am not guessing, nor theorizing, nor repeating something I read somewhere, I am talking about actual experience shooting Benchrest against some very good competition. :)
 
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Regarding those "clicks" used to set powder measures' chambers to the volume desired, it reminds me of when benchresters often added or subtracted a click.

Bullets were shot just fast enough in a given twist to spin them just enough to stabilize in the ambient temperature. If they shot in cooler temperatures, a click or two was added to put more powder in the case. Colder air makes it thicker and bullets need to be spun a bit faster to keep them stabilized all the way to the target. A click or two less would be used in hotter temperatures.

The more rpm' a bullet has, the more unbalanced they are the more the jump off the bore axis due to centrifugal forces.

================

This thread reminds me of those about neck only sizing bottleneck cases versus full length sizing them for best accuracy. They're typically about which way makes the case fit the chamber better. I think the icing on that conversational cake was when benchresters finally started full length sizing their fired cases not too long ago. They do center case necks and therefore bullets better in the bore when fired. Their smallest groups stayed the same size. Their biggest ones shrunk to lower dimensions.
 
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Lake City settled for a Winchester ball powder that metered to half the weight spread that Remington's extruded powder had in M118 Match ammo whey they operated the arsenal. Winchester's stuff shot worse than Remington's did.*
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Makes me wonder if the winchester would have shot better than the remington if the weight spread was doube vs half.
 
jmorris said:
Makes me wonder if the winchester would have shot better than the remington if the weight spread was doube vs half.
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Doubtful. I don't have anywhere near Bart B's experience, skill or knowledge, but I don't remember anybody ever telling me they use ball powder when loading long-range ammunition. The general consensus among the prone shooters I used to hang out with is that extruded powder gives better accuracy, even at larger charge weight variances. Unfortunately I don't remember much more than that at this point, it was a few years ago and we didn't discuss it very often.

I will say that in loading my 600-yard ammo for .223 (80-grain Nosler HPBTs and stiff charges of Varget or RL-15) I tried weighing and trickling my charges exactly once. That box of 50 never yielded a score any better than I got by just being mindful of how consistently I ran my powder thrower.

(Incidentally, the 2 things that DID improve my prone scores were a couple seasons of 50-foot indoor smallbore and learning to single-load my Service Rifle without breaking position between shots.)
 
Ball powders are typically harder to ignite and burn uniformly unless they get a lot of heat to start with. It's harder to make really hot primers uniform in fire output. This all ads up to an initial pressure spike that slams the bullet harder into the rifling. And that deforms bullets more than a gentler one.

Several people observed this using Oehler pressure systems measuring their hand loads.
 
Bart B. said:
Ball powders are typically harder to ignite and burn uniformly unless they get a lot of heat to start with. It's harder to make really hot primers uniform in fire output. This all ads up to an initial pressure spike that slams the bullet harder into the rifling. And that deforms bullets more than a gentler one.

Several people observed this using Oehler pressure systems measuring their hand loads.
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I wondered about the reasons ball powders, extruded powders and flake powders coexist without one overtaking the others in the hearts of reloaders.

What is your opinion; Is the reason ball powders are still popular that the meter easier than extruded? Or is there some other virtue I don't know about?

I have no axe to grind, just curious. But it would shed some light on the original question of this thread, you think?

Lost Sheep
 
Stick powders rule at long distance. Ball powders can do well at short distance. Quite a number of us tried Tac in 6PPC when it came out, and it could shoot some tiny groups, but was sensitive to humidity and didn't seem as consistent as N133 to me. I was talking to Don Geraci at a shoot and he told me he had shot some of his tiniest groups with TAC, but would get unexplained "fliers" with TAC that didn't happen with N133, so he went back to N133, as did most folks.

Are there any flake rifle powders?
 
It's my opinion that most reloaders think that precise charge weights means consistent muzzle velocities. And they can buy scales to measure charge weight to 1/1000th grain very easily. Doesn't matter that their hand held rifles shoot bullets with three to four times the muzzle velocity spread than if shot in free recoil.

Most folks in that group don't realize that a reasonably consistent volume is good enough. The fact that benchrest records through 300 yards are set with metered charge weights with a 2/10ths grain spread is something they cannot comprehend.
 
Bart B. said:
shot just fast enough in a given twist to spin them just enough to stabilize in the ambient temperature...

The more rpm' a bullet has, the more unbalanced they are the more the jump off the bore axis due to centrifugal forces...
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Thx bartb this is useful, tends to reinforce my speculations regarding twist and stability. BTW making progress on "splits" described on earlier thread, thx for constructive criticism - TH

An interesting thread and worth reading.
 
TH, one other thing on velocity and its spread's effect on accuracy.

A 50 fps spread in a .308's muzzle velocity will cause a 1/10th inch vertical shot stringing at 100 yards due to bullet drop. People chronographing such loads at 100 yards oft times wonder why slower bullets sometimes strike higher in their 100 yard test groups. It wasn't the muzzle velocity that shot that bullet high. Something pointed the barrel to put it there.
 
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Bart B. said:
chronographing such loads at 100 yards oft times wonder why slower bullets sometimes strike higher...
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I'm familiar with this interesting phenomenon, still learning of it's significance and implications for the reloader.


murf - recoil!
 
Slower bullets striking higher?

The explanation I have heard is:

Most bullets' recoil move the muzzle upwards.

The longer the bullet remains in the barrel, the longer the time the muzzle has to move upwards, thus the higher the barrel is pointed when the bullet exits. (e.g. Barrels firing slower bullets point higher by the time the bullet exits.)

The upward displacement of the barrel due to the increased momentum of the faster bullet is LESS than the amount of upward displacement of the barrel at the (later) time of the exit of the slower bullet. (This is especially true if the higher velocity bullet achieved that velocity by being a lighter bullet.)

Thus, the slower bullet exits the barrel when it is pointed at a higher/steeper angle than the faster bullet.

Eventually the paths of the bullets (point of impact) will cross each other, MAYBE. It depends on how fast the bullet sheds velocity. They may both hit the ground before their points of impact coincide.

That is how it has been explained to me and my analysis of the theory and observations in the field do not contradict it.

I hope my extended explanation illuminates more than confuses.

Thanks for reading.

Lost Sheep
 
Lost Sheep has the right idea, but I was referring to why sometimes slower bullets strike higher. His comment was about all slower bullet striking higher. That's called positive compensation; over a century ago, the Brit's proved that happened with their SMLE's loaded with ammo having a huge muzzle velocity spread. Here's an article on it; click on the "PDF" screen button in the "Download Options" window:

http://archive.org/details/philtrans05900167

The initial muzzle axis movement is down, then it goes up. With the right kind of barrel, cartridge and how the rifle's held, all the bullets will exit on the muzzle axis down swing. The last few inches of the muzzle axis vibrates about 3 to 4 times as fast as the barrel's resonant frequency. It's explained in:

http://www.varmintal.net/amode.htm

I was referring to only some of the time that happened.

Walkalong's comment is about the shooters shoulder. If the rifle's butt is placed lower in the shoulder, that will cause the muzzle axis to rise enough to let any bullet strike higher. There's less resistance (solid bone structure) there compared to higher up where there's more bones having more resistance. Long range shooters producing best scores have already learned that relative to the shoulder, a high "butt" goes low and a low "butt" goes high. I had to learn that myself.
 
With a good rifle and load, 99+% of errant shots are our fault. The sooner we learn that and stop blaming the gun/load/scope/brass/etc, the sooner we start getting better.

Of course, occasionally it is something else. It all just takes practice. :)
 
Geoffrey Kolb (Border Barrels, Great Britian) has a web site that calculates how a given .308 Win. chambered barrel whips and wiggles fired in free recoil in free space and unconstrained by any rests or clamps as it recoils. Different barrel profiles' dimensions can be entered. It shows that if the center of gravity of what holds the barrel is on the bore axis, the barrel will not whip nor wiggle at all:

http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/barrel_vibrations.htm

See what the muzzle axis angle is at about 1.2 milliseconds which is typical for the .308 Win cartridge.
 
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In David Tubb's High-Power Rifle Reloading, he states that the weight of the powder charge is the least important factor in accurate reloads. I never met David Tubbs, but I saw his name in the sign in book at Buffalo Creek a few times.
One of the indications that you have a good load (appropriate burn rate and charge), is that variations in powder weight don't make much difference:
http://www.6mmbr.com/laddertest.html
I throw ball powders from a measure, checking them every seven or eleven rounds to see how it's going. Extruded powders I throw a few tenths of a grain light and top them up with a tickler. I usually go for ±0.1 gr as a simple(istic?) apparition of the use of a digital scale. :p
 
Tubb's positon on charge weights are the same as Lake City arsenal 7.62 NATO M118 match ammo. Learned this when talking with one of their ballistics engineer regarding a bad batch of lot 12064 match ammo. He said when they get a new lot of IMR4895 to load, they test for velocity more than accuracy. A grain or two difference shows insignificant accuracy shooting 270-shot test groups. But they pick the charge weight that has met velocity specs of 2550 fps +/- 30 fps at 26 yards so sight dope on the M14's and M1's shooting it will be close enough to not matter across all lots of ammo. The spread of peak pressure about 50,000 CUP for specs is still met.
 
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