Something to Ponder. One powder vs Another?

[Rule3]

Why is one powder supposedly more accurate than another?

First off this is not about someones favorite brand of powder.

With all the makes, brands of powder out there I would think that powders of similar burn rates would be equal (accuracy wise)regardless of who makes it, They all have the same science or chemistry, there are no real secrets in the making of powder.

Some manuals have the "most accurate load/powder" so lets go with that, all other things exactly equal. Same gun in a ransom rest, same primer, same brass same bullet.

So if powder A delivers x velocity. And Powder B also delivers X velocity. The velocities are the same and lets also say the powders measured may be of course different weights but similar burn rates and the pressure is the same give or take the variable of different burn rate but within the range of the cartridge. Lets say max pressure to make it easy.

So we have both powders yielding X velocity or FPS and the same internal pressure.

Would not accuracy then be determined buy the gun barrel and the coefficient of the bullet? They are both going the same speed.?

Again this not a "I like this powder or that powder" tying to keep it "generic"

To me powder burns, produces pressure and the bullet moves. Powders of similar burn rates also do it it in the same amount of time (to burn)

Once the bullet is out of the barrel how can the powder be an influence on accuracy??

 

[lauderdale]

Temperature sensitive/position sensitive have any room in this? Now ive learned from you fellas and still am.

 

[jmr40]

In my experience this is pretty much the case. I have loaded 30-06 with IMR4350 H4350 and Ramshot Big Game. All are very similar, all give nearly identical speed and accuracy in several rifles I've shot loads from. I've noted similar results in 308 loading Varget, RL15, IMR4064 as well as a couple of other powders.

I think you may see some differences when comparing ball and stick powder.

 

[Bart B.]

I'm convinced that.......

Each powder used in a given cartridge with a given bullet will produce a different shaped pressure curve on the bullet until it exits. As long as the powder's pressure curve is the same shape in time vs pressure level, the barrel will be at the same place for every shot and the bullet departs repeatably at that point.

Some powders do better in that regard than others. While two or more powders with near equal burn rates may produce the same peak pressure and bullet velocity, if their pressure curves are not the same, one may well produce better accuracy than the others.

Very slow powders often shoot bullets out at higher muzzle velocities, but oft times the bullets are launched at different angles relative to the line of sight because their pressure curves are not consistent; they don't shoot bullets very accurate. Which is why powder burn rates in upper half to three fourths range of their burn rates listed tend to do best accuracy wise but not shoot bullets as fast as slower powders do.

The start up pressure rise with some powders tends to slam bullets harder into the rifling than others. Back when Oehler introduced their pressure measuring system, some folks reported seeing a much sharper rise in pressure at the start of the curve. They surmised that slammed bullets harder into the lands than powders producing a gentler push on the bullets. Ball powders were reported notorious for doing that. It was compounded by having to use hotter primers to get ball powders to burn uniformly. I think Winchester's primers are hotter than most because of their ball powder's low "ignition index," if there is such a thing.

All the above aside....

Powders need to be ignited uniformly. Weak firing pin springs slam the pin into primer cups with less force. That starts detonating the pellet less uniform. And that uneven flame time and temperature curve doesn't ignite the powder uniformly. Some long range competitors have noticed their favorite load begins to show elevation stringing but replacing the firing pin strings brings good accuracy back to greatness.

 

[Rule3]

Well lets narrow or refine it down a little more. Lets stick with handguns and powders that fill the cases pretty much full. Say the common 9mm and 45ACP.

Not some ultra fast powder that only uses a few grains The medium to slower burners, If the case is 80% full or more than powder position really does not apply,

 

[forestswin]

Interesting question.
I looked in Lyman Cast Bullet Handbook 4th Ed to make some comparisons.

sorry, no answers, just more questions

for the 45 acp 200 gr lead bullet
Lyman mold #452630 shown on page 277
the test firearm used was the Universal receiver, 5" barrel length, 1-16 twist rate, 0.450" groove diameter

the max load data shows
BE 6.0 grains
909 fps
17,000 CUP

Unique
7.5 grains
913 fps
17400 CUP

those numbers are pretty close

I don't think BE and Unique are in the same burn rate grouping.
BE is the 45 acp standard powder - does Unique do as well?
Or are different factors in play here?

I also looked at the MSDS sheets for BE and Unique.
The percentage range of nitrocellulose and nitroglycerin they list is for all their powders, they dont give data for specific powders.....so thats no help.

its all just frustrating voodoo science :banghead:

 

[Rule3]

OK, good example. True they are different burn rates but both powders are used a lot in the 45 ACP

So, based on that, the velocity is pretty much the same, so will one be more "accurate" than the other"?? That is the crux of my question??

I do not think one is inherently more accurate than the other,.

 

[Steve C]

Why is one powder supposedly more accurate than another?

The way I see it for what its worth.

Accuracy is defined as shot to shot uniformity on target. To achieve that uniformity the more uniform the shot to shot pressures are the more "accurate" the ammo should be. The problem with ammo is that there is always variation in the components, including the powder from lot to lot which produces variation.

Different powders have different burn rates, ignition characteristics and volume densities. Each component mix of caliber, case, primer and bullet will have different interior volume and dimensions.

How uniform from shot to shot a powder burns and produces pressure will depend upon its relationship to the components, its position in the case, its relationship to the bullet size and weight and the source of ignition, and where any excess unfilled case volume happens to be at the time of ignition, all of which effect the consistency of the pressure produced when it burns. This is one of the reasons a powder that fills the case is generally more accurate than one that leaves more unfilled volume. The powder forward, powder rearward difference is a commonly noted phenomenon. A particular powder or several powders will have the optimum characteristics to produced uniformity with the particular characteristics of the components of the caliber being used. That is going to be the "most accurate" powder choice most of the time. Different powders will work best with different caliber ammo.

 

[Blue68f100]

Not really true with BE shooting loads in a 45acp. Most all BE loads used in competition are below min starting loads published, using fast burn powders. All they are doing is generating enough velocity to stabilize the bullet. The loads may be considered mouse farts but are extremely accurate and do not come close to filling the case. Now I have see very accurate loads using the same powder and pushing the bullet to near max load. There are way to many variables to list when it come to a auto loader. When it comes to auto loaders I think its way more important to have consistent lockup. Which includes the 1st round where most discard when shooting for accuracy test.

With auto loading rifles (gas operated) your dealing with pressure that effects the timing and harmonics. Ejecting a cartridge that is hot and still under pressure. Which does not happen with a bolt gun. Not all powders work and in most cases are lower charged than a bolt gun.

As far as accuracy published loads I have not found one that has worked for me. I do try them to see if I get lucky but it never happens. I always end up working up my loads anyway. But like most I find the most accurate loads near max.

 

[Mauser69]

There are just too many variables for this to be as simplistic as this thread tries to suggest, and the biggest variable is each individual gun - a variable that no one has any way to quantify.

Every single gun has different vibrations and resonances that cause it to point at different places during each microsecond of the firing process. And of course recoil and the upward movement of the muzzle will always exist. The exact instance when the bullet actually leaves the muzzle and is no longer subject to the changes in the gun is almost a total crap shoot, but it WILL have similarities from one shot to the next when all else is equal.

And since each exact combination of load produces slight differences during the explosion process that creates shock waves, pressure curves, etc., those unique variations in each individual gun react uniquely with each load. Even in a fixed rest, the only variable you have removed is the shooter's skill, but you have then ADDED the variables associated with how the solid rest vibrates and resonates, and how that clamping affects the way the gun vibrates and resonates. It is entirely possible for a gun to shoot a specific load differently in a fixed rest than it does with a somewhat looser hold for reasons NOT associated with the shooter's skill.

 

[Rule3]

So, what I have read so far is that it seems that no one powder is "inherently more accurate than another" (within accepted powders for a specific caliber.)

Did not want to get into names but lets say in 45acp, Bullseye, HP38 and Unique. (there are others)
They are all slightly different but can produce the same "accuracy" all other things the same.

So from that, I infer that powder likes and dislikes is mostly anecdotal or just a matter of what is available and what someone is used to using.

I have not done extensive testing on the results of different powders only testing with the amount of a specific powder as most folks. I can load HP 38 or Bullseye and still shoot the same accuracy (or lack of)

 

[bluetopper]

The differences in accuracy is much more telling in rifles than handguns and the greater the distance the greater the difference you can tell.
The difference in powders is discernable in handguns also if you benchrest them at 25 yards and more telling if you bench them at 50 yards. I'm not referring to snub nose revolvers or small carry guns.

 

[rbernie]

Some powders simply have a more uniform ignition pattern and a more linear flame front propagation than others. Others are more energetic, i.e. release more energy over the time window available for propelling the bullet out of the barrel, and yet have more variable flame front propagation rates.

That is why some powders are faster in a given chambering for a given peak pressure level, and some powders are more accurate.

 

[Rule3]

Some powders simply have a more uniform ignition pattern and a more linear flame front propagation than others. Others are more energetic, i.e. release more energy over the time window available for propelling the bullet out of the barrel, and yet have more variable flame front propagation rates.

That is why some powders are faster in a given chambering for a given peak pressure level, and some powders are more accurate.

Granted all the above is true, however if 2 powders are loaded to yield the same velocity(FPS) then I can not grasp why one or the other is "perceived" or actually is "more" accurate??

As to rifles, perhaps benchrest shooters or those with awards can tell the difference but I still do not understand say a 556 loaded with brand A or Brand B is going to matter either?

 

[Bart B.]

Back when I shot outdoor pistol and queried some National Champions about testing ammo, both said to get a Ransom rest then secure it very hard into a heavy bench. That eliminates their holding and trigger pulling variables. They shot their winning and record setting scores with .45 ACP wadcutter commercial ammo testing well under 2 inches at 50 yards from such machine rests; handloads never shot that accurate. Their groups on target at 50 yards shooting the same M1911's were 4 to 5 inches. Their .22 rimfire pistols tested 1/2 inch at 50 yards but shot 3 to 4 inches hand held.

Regarding the following:

With auto loading rifles (gas operated) your dealing with pressure that effects the timing and harmonics. Ejecting a cartridge that is hot and still under pressure. Which does not happen with a bolt gun. Not all powders work and in most cases are lower charged than a bolt gun.

A barrel's harmonics (wiggling and whipping frequencies while the bullet goes through it) is 100% repeatable from shot to shot as long as the parts fit together the same way for every shot. Well built match grade versions wouldn't shoot inside 4 inches at 600 yards with good lots of commercial match ammo if all the parts didn't go back in battery perfectly each time. M1 and M14 rifles' bullets are several feet out the barrel when their bolts start to open. Pressure in the barrels is near zero when that happens.

From Springfield Armory Technical Note SA-TN11-1094 dated 16 Dec 1957

Three single rounds were fired from each of three M1 and three M14 (T44E4) rifles. The ammunition used was M2 AP for the M1 rifles and armor piercing (T93E1 or T93E2) cartridges for the M14 rifles. Each rifle was fully loaded for each series of three shots. High speed motion picture cameras (operating at 6,000 to 7,000 frames per second; about 1 frame every .015 millisecond) and flash strobes were used to record hammer fall, bullet exit, operating rod movement and bolt unlocking during each firing sequence. Lumiline screens were used to record average bullet velocity at a distance of 53 feet forward of the muzzle. The film was analyzed to obtain the data below. Average values were computed from the high speed film as follows:

Data Item ..........................................................M1 Rifle ................................M14 Rifle
Type of gas system .............................................gas impingement ...................gas cut-off and expansion
Location of gas port from muzzle ..........................1.5 “ .....................................8.0 “
Gas port diameter ...............................................0.0793 “ ...............................0.0768 “
Barrel length ......................................................24 “ ......................................22 “
End of hammer fall .............................................0 milliseconds ........................0 milliseconds
Bullet passes gas port .........................................1.31 milliseconds ....................1.01 milliseconds
Bullet clears muzzle ............................................1.36 milliseconds ....................1.25 milliseconds
Initiation of operating rod recoil ............................1.58 milliseconds ....................1.53 milliseconds
End of operating rod dwell* ..................................2.89 milliseconds ....................3.57 milliseconds
Completion of bolt unlocking ................................4.07 milliseconds ....................5.00 milliseconds
Amount of bullet travel at start of op rod recoil .......7.2 “ past the muzzle ..............9.2 “ past the muzzle
Position of bullet at end of op rod dwell* ................50.2 “ past the muzzle .............76.1 “ past the muzzle
Position of bullet at completion of bolt unlocking .....88.9 “ past the muzzle ............123.0 “ past the muzzle
Average bullet velocity ........................................2735 feet per second ...............2733 feet per second

* Dwell time is the time required for the rearward travel of the operating rod prior to unlocking the bolt.

Regarding pressure in bolt guns vs. semiautos, commercial and military ammo's loaded to virtually the same exact pressure for .308 Win/7.62 and .30-06 ammo respectfully. Commercial ammo makers don't know what type of rifle their stuff will be shot it so it's made to work safe and reliably in all rifles. Military rifle teams oft times used reloads at near proof load pressures in M1 and M14 rifles

 

[Rule3]

Bart,

The above is all good information but it goes to the variables of the gun and barrel, gas systems etc.

The first part of using a ransom rest is what I originally posted and then changing only the powder to produce the same velocity.

So in those tests of the 45 did it matter if they used one powder or the other? Did they all use the same powder and same charge?? Or did some use say BE and others HP38 or Unique whatever??

 

[bluetopper]

My opinion and experience, shooting a 1911 in a ransom rest at 50 yards, you bet powder choice makes a difference.

 

[Rule3]

My opinion and experience, shooting a 1911 in a ransom rest at 50 yards, you bet powder makes a difference.

What does that tell us though?

If the Sun does not come up tomorrow that will make a difference.

 

[Bart B.]

Rule3, the top pistolsmith at the USN Small Arms Match Conditioning Unit told me that there was little accuracy difference between lots of Remington 45 wadcutter match ammo (best made then), but the best lots were used by the teams going to the Interservice and National Matches.

That ammo was probably adjusted for charge weight by Remington for best accuracy and it was a DuPont powder; which one, I don't know. Never heard of anyone winning at the NRA Pistol Nationals using hand loaded ammo. Nor of anyone handloading 45 ACP ammo that shoots 2" or under at 50 yards all the time in 45 ACP pistols. Bullseye was popular for both 45 ACP and 38 Special handloads with lead wadcutter bullets

 

[Rule3]

What ammo does Les Bauer shoot to maintain a 3" accuracy guarantee at 50 yards? Or even better 1.5"

 

[Dudedog]

I am just convinced some guns like some powders better
I sure there is some scientific reason, pressure curve, barrel harmonics etc.


I get great SDs with BE86 but my pistols seem happier with some powders with that give higher SDs.
So while BE86 does not work great for me , other people have had different results and really like it. (just using BE86 as a example)

 

[forestswin]

based on Bart B's statement

"As long as the powder's pressure curve is the same shape in time vs pressure level, the barrel will be at the same place for every shot and the bullet departs repeatably at that point."

Can pressure curves be duplicated with different powders by adjusting charge weights?

 

[Rule3]

There are just too many variables for this to be as simplistic as this thread tries to suggest, and the biggest variable is each individual gun - a variable that no one has any way to quantify.

Every single gun has different vibrations and resonances that cause it to point at different places during each microsecond of the firing process. And of course recoil and the upward movement of the muzzle will always exist. The exact instance when the bullet actually leaves the muzzle and is no longer subject to the changes in the gun is almost a total crap shoot, but it WILL have similarities from one shot to the next when all else is equal.

And since each exact combination of load produces slight differences during the explosion process that creates shock waves, pressure curves, etc., those unique variations in each individual gun react uniquely with each load. Even in a fixed rest, the only variable you have removed is the shooter's skill, but you have then ADDED the variables associated with how the solid rest vibrates and resonates, and how that clamping affects the way the gun vibrates and resonates. It is entirely possible for a gun to shoot a specific load differently in a fixed rest than it does with a somewhat looser hold for reasons NOT associated with the shooter's skill.

I do not really know how to take your reply as :

There are just too many variables for this to be as simplistic as this thread tries to suggest, and the biggest variable is each individual gun - a variable that no one has any way to quantify.???

I am well aware of all the other variables and fully realize that they have more to do with accuracy than anything,

The whole "simplistic" point was to determine if there was any basis of fact that one powder (of similar burn rate composition) is any better than another given all other variables the same.

I find it very simplistic to just say it is a "crap shoot"

 

[Andrew Leigh]

Rule3,

When it comes to rifles there are some basic things to consider. Powders are designed with burning rates that will propel a particular range of bullet weights down a particular range of calibres within comfortable pressures. So a particular powder can be a best fit for a couple of bullets weights / calibres.

Heavier bullet - Slower burning powder
Lighter bullet - Faster burning powder
Select a powder the fills the case by more than 85%
Select a powder that is not readily affected by temperature changes

So by way of example my .375 I experimented with 3 local powders and a 300gr Accubond. I also wanted to be at 2 500fps if at all possible;

S335 - Burning rate of .6325
S355- Burning rate of .5000
S365- Burning rate of .4400

So when aiming for the same velocity these were my results and groupings were poor;
S335, 65.2gr / 98% fill / 67 243psi / 2 500fps / 1.191ms barrel time
S355, 66.4gr / 99% fill / 57 526psi / 2 500fps / 1.254ms barrel time
S355, 71.0gr / 105% fill / 50 054psi / 2 500fps / 1.294ms barrel time

Now I know that the optimum barrel time for my .375 is 1.247ms. So when aiming for barrel time rather than velocity this is what I get.

S335, 62.7gr / 94% fill / 60 160psi / 2 427fps / 1.248ms barrel time
S355, 66.7gr / 100% fill / 53 695psi / 2 510fps / 1.247ms barrel time
S355, 72.8gr / 107% fill / 54 577psi / 2 561fps / 1.246ms barrel time

All loads are pretty much the same in accuracy. The middle load gives my desired velocity. But note that the barrel time is the constant and not velocity. So the accuracy thing comes in for me when you meet a specific requirements with different powders.

I hope this makes sense.

 

[bluetopper]

What does that tell us though?

If the Sun does not come up tomorrow that will make a difference.

It tells us that one pistol powder shoots smaller groups than another one. Isn't that what you are after?