Powder Position Sensitivity

[joeb33050]

POWDER POSITION SENSITIVITY TESTING

Does the position of the powder in the cartridge case affect muzzle velocity, (MV); does powder position affect the standard deviation, (STDEV) of MV; and does that position affect accuracy?
Powder is moved to the FRONT of the cartridge case by holding the rifle at ~ a 45 degree angle and slapping the side three times, then putting it carefully on the rest.
Powder is positioned LEVEL in the case by putting the rifle on the rest and slapping the side ten times.
Powder is positioned to the REAR of the case by pushing a wad down on the powder.
I recommend cotton but use Dacron wads. Use as small a wad as works. I use a teased wad about dime to penny size, and push it on top of the powder with a pencil.
These loads, 15 of each last time out, are shot at 100 yards over my PACT chronograph.
I'll record all results on an EXCEL workbook called "POWDER POSITION SENSITIVITY" and a WORD summary, this is it, called " POWDER POSITION SENSITIVITY TESTING". (See the EXCEL workbook for all the information about the loads and results.)
These two files will be on http://sports.groups.yahoo.com/group/CB-BOOK/
in FILES,
in ERRATA

Testing to date:
2/6/08, 7.0 Unique, .30WCF M54 Winchester

LEVEL
MV(fps) 1214
MV STDEV (fps) 39.3
GROUP AVG (") 2.33
FRONT
MV(fps) 1195
MV STDEV (fps) 28.1
GROUP AVG (") 2.51
REAR
MV(fps) 1185
MV STDEV (fps) 14.3
GROUP AVG (") 2.25

2/20/08, 8.5 Unique, 30WCF M54 Winchester

LEVEL
MV(fps) 1365
MV STDEV (fps) 18.8
GROUP AVG (") 2.65
FRONT
MV(fps) 1346
MV STDEV (fps) 16.1
GROUP AVG (") 1.35
REAR
MV(fps) 1378
MV STDEV (fps) 29.5
GROUP AVG (") 1.84

2/20/08, 10.0 Unique, 30WCF M54 Winchester

LEVEL
MV(fps) 1519
MV STDEV (fps) 22.3
GROUP AVG (") 1.68
FRONT
MV(fps) 1502
MV STDEV (fps) 28.8
GROUP AVG (") 1.56
REAR
MV(fps) 1498
MV STDEV (fps) 19.5
GROUP AVG (") 2.24

The bullets were tipping.
There's nothing here suggesting that powder position has any predictable affect on MV or MV STDEV or group size. Next on the schedule is the 45/70 and Unique. Always looking for more experimenters.
joe b.

[selmerfan]

I tried this with my .454 Casull and light Unique plinker loads as well. I couldn't discern a difference either, some different numbers, but nothing to throw a hunting load off. If you had posted this info over at benchrest.com, the response might be different. :)
Selmerfan

[HORNET]

Joe,
What Boolit? Any crimp? How far off the rifling or in contact? All these affect initial combustion and could alter the results.

[fourarmed]

Joe, I predict that as long as you are using Unique, you won't see any very dramatic differences. That is after all one of the reasons we use it so much. Slower burning powders - especially ball powders - will give you more dramatic differences. I remember one time in particular testing H-380 in some large, blackpowder case. If I pointed the barrel up before firing, velocity spread was tolerable - less than 100 fps. Shooting however it happened to lie in the case gave a spread of around 300 fps WHEN IT WENT OFF AT ALL.

[35remington]

Try something like IMR or H4227 and be prepared for a very noticeable variation. Even in something as dinky as a .25-20 case. Bigger cases are, of course, worse.

Like the other posters said, Unique is better than most in being position tolerant.

Leave out the dacron wad next time and just orient the powder in the back by tipping the muzzle up; that way the test is apples to apples with no dacron that some may accuse of affecting the results somehow.

The slow pistol/fast rifle powders will show enough velocity variation (100-200 fps or more) that dacron is used with many of my loads to keep the powder oriented.

[HORNET]

Joe,
I think that the position sensitivity also depends on the primer type and case volume. If you were using large rifle mag primers with that Unique, I bet you'd see a lot less difference than if you were using a mild large pistol primer. Or it could get 'lost in the noise'.
You can also have more fun drilling out flash holes when you get bored. There's been lots of discussion of that in the past. I haven't checked what the chrony says but there is a distinct difference in grouping with some powders.

[shooter93]

I'll second the Unique post...I doubt you'll see much difference when using it. I've never had anything as consistent or as accurate in 38/40...44/40...44 Special or 45 Colt. I've fired tons of cast bullets through a suppresed rifle in 45-70. I've tested a number of different powders. Bullet weights ran from 400 to 575 grains. The Unique loads were far and away the best. No fillers, they were tried, powder charges rarely exceeded 15 grains, they were all sub sonis loads. The rifle will clover leaf 5 shots at 100 yds...that's sub moa and it carries that to 300 yds which is as far as we've group tested it. Extreme spread is generally around 6 to 12 fps. It was built on a Number 1 action with a 16-1/2 inch barrel and an SSK supressor on it.

[joeb33050]

POWDER POSITION SENSITIVITY TESTING

Does the position of the powder in the cartridge case affect muzzle velocity, (MV); does powder position affect the standard deviation, (STDEV) of MV; and does that position affect accuracy?
Powder is moved to the FRONT of the cartridge case by holding the rifle at ~ a 45 degree angle and slapping the side three times, then putting it carefully on the rest.
Powder is positioned LEVEL in the case by putting the rifle on the rest and slapping the side ten times.
Powder is positioned to the REAR of the case by pushing a wad down on the powder.
I recommend cotton but use Dacron wads. Use as small a wad as works. I use a teased wad about dime to penny size, and push it on top of the powder with a pencil.
These loads are shot at 100 yards over my PACT chronograph.
I'll record all results on an EXCEL workbook called "POWDER POSITION SENSITIVITY" and a WORD summary, this is it, called " POWDER POSITION SENSITIVITY TESTING". (See the EXCEL workbook for all the information about the loads and results.)
These two files will be on http://sports.groups.yahoo.com/group/CB-BOOK/
in FILES,
in ERRATA

In 30WCF, UNIQUE, there was no indication of MV difference as powder position changed. Today's test was of only LEVEL and REAR powder position, and it looks like MV varies with powder position for both UNIQUE and SR4759 in 45/70.

On 2/27/08: C. Sharps 45/70, 457193 Cast 2/24/08, Avg. 407.0 Grains, 406.5-407.4 Grains, 2.705" OAL, WLP, Blowing fiercely!!!!

DATE 2/27/08 2/27/08
POWDER Unique Unique
GRAINS 14 14
POSITION LEVEL REAR
MV AVG(FPS) 1195 1240
MV STDEV(FPS) 28.0 15.8
GROUP AVG (") 2.43 3.43

DATE 2/27/08 2/27/08
POWDER SR4759 SR4759
GRAINS 22 22
POSITION LEVEL REAR
MV AVG(FPS) 1128 1310
MV STDEV(FPS) 35.5 31.8
GROUP AVG(") 1.93 2.48

joe b.

[mroliver77]

Most of my shooting is aimed at(pun intended) hunting. When loading hunting rounds with reduced charges of pistol powders I get way too much poi difference without fillers of something to hold powder to the primer. When one shot could be pointing down and the next level or pointing up into a tree and the gun could be thrown to the shoulder or gently raised to shooting position, this is where I see the problems worst effects. With a foam disc cut from a meat tray or a tuft of dacron I get the same performance without the shot to shot variation.
J

[shooter93]

Your results are s bit different from mine Joe. My extreme spreads are as I posted before. But I am also shooting subsonic velocities.Your group sizes might not mean much with strong winds. I have fired somewhere arond 800 rounds to come up with the loads we now use so i'm fairly confident of the results. I never purposely posistioned the powder charge...simply shot them. I also worry about extreme spread most when load developing and only look at SD much later in the process.

[joeb33050]

Your results are s bit different from mine Joe. My extreme spreads are as I posted before. But I am also shooting subsonic velocities.Your group sizes might not mean much with strong winds. I have fired somewhere arond 800 rounds to come up with the loads we now use so i'm fairly confident of the results. I never purposely posistioned the powder charge...simply shot them. I also worry about extreme spread most when load developing and only look at SD much later in the process.

What I'm trying to do here is get some data on powder position and MV, to substitute for the opinions we all have.
Next week is IMR4227 in the 30WCF.
Any other experimenters out there willing to try?
Thanks;
joe b.

[Bass Ackward]

What I'm trying to do here is get some data on powder position and MV, to substitute for the opinions we all have. joe b.


Joe,

What you are going to find out is that based upon all the variances from size to hardness to bullet design and weight. Lightest bullets per caliber will show the greatest effects. Seating into the lands will allow you to go lower too because it will take higher pressure before it starts to move out ensuring better ignition.

So position sensitivity is going to occur at different points for different people in different guns of the same caliber. There is no such thing as a powder that is position sensitive. It is a reloader developed phenom based upon his conditions.

[lovedogs]

My only experience with this is using the .45-70. I first noticed it when trying to use low-recoil loads with 500 gr. cast bullets and H4198 for long-range silhouettes. With a small enough powder charge to keep recoil and leading down and still maintain acceptable accuracy I had to tip the muzzle up before each shot. This started me on my unscientific research on position sensitivity.

My method was to shoot groups while using a Chrony, shooting on the level and down steep hills.

I first researched H4198. I found it was too position sensitive unless I used charges heavy enough that I began experiencing too much leading and more recoil than I wanted for 50 shots in a row, like at a match. In match shooting I use a 1:20 alloy and a naked base.

About now someone will chime in about using fillers. I've stated my position on this many times. After talking with ballistic experts who have more experience, education, and testing equipment than I, I've decided to follow their advice and NEVER USE FILLERS WITH SMOKELESS POWDER.

Next, I performed the same experiments using RL7. It had almost the same results as the H4198. When I tried it using a lighter 300 gr. jacketed bullet, a heavier charge, and a mag primer the RL7 worked really good. But with cast and small charges it was also position sensitive.

Then I tried 5744. At first I was concerned about the dirty burn but when I learned to ignore it I was well satisfied. No need for a filler. No mag primer. No crimp. No matter what the position it shot the same and shot very well.

Now I use 5744 with all cast loads and RL7 with jacketed. When the weather warms up I plan on trying heftier hunting loads using a light 350 gr. RNFPGC with RL7. I think it might work okay and give a cleaner burn than the 5744 in this type of load. While shooting in a match it's no big problem having unburned powder roll back into the chamber. I can just puff it out and load the next round. But when hunting it could slow me down if I ever needed a second shot. I can't imagine why I'd want to shoot anything twice with a .45-70 but you never know; I might miss some day and want a second shot.

[joeb33050]

Joe,

What you are going to find out is that based upon all the variances from size to hardness to bullet design and weight. Lightest bullets per caliber will show the greatest effects. Seating into the lands will allow you to go lower too because it will take higher pressure before it starts to move out ensuring better ignition.

So position sensitivity is going to occur at different points for different people in different guns of the same caliber. There is no such thing as a powder that is position sensitive. It is a reloader developed phenom based upon his conditions.

Do you have any DATA???(I understand that you believe that there are too many variables to ever develop a rule re cast bullets. Why don't we just call this BA RULE 1, you can quote that and not have to type the mantra in response to every topic?)
joe b.

[shooter93]

I understand Joe. The difference being you are purposely positioning the powder and I didn't do that. Considering the very low extrem spreads I got with these loads I seriously doubt powder postion would have dropped it below 6 fps. The first 500 or so rounds were shot with bullets that were as close to humanly possible to cast. They were cast from one alloy....one mold...weighed less than .1 gr difference within each group and were loading as match ammunition...brass prep and all. After that bullets weren't quite as perfect....5 or 6 tenths difference per group...on ocassion a full grain or two... but shot extremely well too. The number of bullets cast to get that many near perfect bullets was staggering but I had a volunteer caster who casts very well and enjoys it. The trouble here is although I fired a huge number of rounds...it's one rifle and caliber. Will I try this again with another rifle?....doubtful at this point...I'm working on a 35 krag again. I do have a 300 Whisper to ring out too but in that case the powders tend to fill it up quite a bit. If I try light loads of faster powders I'll let you know.

[Bass Ackward]

Do you have any DATA???(I understand that you believe that there are too many variables to ever develop a rule re cast bullets. Why don't we just call this BA RULE 1, you can quote that and not have to type the mantra in response to every topic?)
joe b.


Joe,

Well, are you using magnum primers or standards? What brand? What lot number? Quite a bit of variance just in standard rifle primers from flat to flat. How heavy is your firing pin strike? How tight is your headspace? How do you factor out ignition variance from primer to primer in your position statistics?

What size are the flash holes in your cases? Are they all the same? How heavy is your brass? How much space is around your case when chambered? What is the anneal on your cases? Are they sealing right away or are you losing some pressure?

Are your rifling wide or narrow? What percentage of rifling to groove? Short or tall? What's the angle on the leade? Do you crimp? How hard? Are you shooting bore size bullets, or how much over bore? What's your seating depth? How long is your throat? How rough is the bore?

What is the lot number of your powder? How humid was it when you loaded them? Did you throw the charges or did you weigh each one precisely? How accurate is your thrower with that powder? Is it as accurate as mine, cause mine won't throw Unique to save it's ...? 4759 is another poor choice for this thrower. Using lube? How much and what kind?

What altitude are you? Barometric pressure? Temperature?

When you start using powders for purposes for which they weren't designed in very low density rates, there are a lot of variables to consider. Use a magnum primer and you almost never need a filler. Most of the time I would say that temperature, primer choice and the powder thrower accuracy with light charges cause the biggest variables. But all that other stuff plays a part too. And this took seven minutes to type, so I probably left one or two factors out too. Just to get you thinkin. :grin:

[joeb33050]

Joe,

Well, are you using magnum primers or standards? What brand? What lot number? Quite a bit of variance just in standard rifle primers from flat to flat. How heavy is your firing pin strike? How tight is your headspace? How do you factor out ignition variance from primer to primer in your position statistics?

What size are the flash holes in your cases? Are they all the same? How heavy is your brass? How much space is around your case when chambered? What is the anneal on your cases? Are they sealing right away or are you losing some pressure?

Are your rifling wide or narrow? What percentage of rifling to groove? Short or tall? What's the angle on the leade? Do you crimp? How hard? Are you shooting bore size bullets, or how much over bore? What's your seating depth? How long is your throat? How rough is the bore?

What is the lot number of your powder? How humid was it when you loaded them? Did you throw the charges or did you weigh each one precisely? How accurate is your thrower with that powder? Is it as accurate as mine, cause mine won't throw Unique to save it's ...? 4759 is another poor choice for this thrower. Using lube? How much and what kind?

What altitude are you? Barometric pressure? Temperature?

When you start using powders for purposes for which they weren't designed in very low density rates, there are a lot of variables to consider. Use a magnum primer and you almost never need a filler. Most of the time I would say that temperature, primer choice and the powder thrower accuracy with light charges cause the biggest variables. But all that other stuff plays a part too. And this took seven minutes to type, so I probably left one or two factors out too. Just to get you thinkin. :grin:

Got it! BA Rule 1 has been cited, all experimentation is impossible.
I'll stupidly continue, knowing that no results will have meaning.
BTW, the top post gives a clue as to where some answers may be found.
joe b.

[Whitespider]

There is no such thing as a powder that is position sensitive. It is a reloader developed phenom based upon his conditions.


Wow Bass,
I can’t buy that. My testing was actually primer testing, I was looking for a primer that would minimize the effects of “powder position” in low density revolver loads. I used this procedure;

Test 1- I would fire 30 rounds over a chronograph, tipping the gun back (barrel up) to position the powder at the rear of the case before each shot, recording extreme spread and standard deviation (I was not interested in average velocity).

Test 2- I would fire 30 rounds over a chronograph, this time alternating tipping the gun back (barrel up) and tipping the gun forward (barrel down) before each shot, recording extreme spread and standard deviation.

I tested every primer I could get my hands on, with powders ranging from Bullseye to 2400 and projectiles cast and jacketed. In EVERY case, with EVERY powder/primer/projectile combination, test 2 showed significantly higher ESs and SDs. Some powder/primer/projectile combinations were much worse than others, but all showed enough difference that it couldn’t be statistical chance. In some cases the ES and/or SD would increase as much as 500%. Several of the tests that showed less than a 200% increase were run again, same results, so I quit running duplicate tests.

[felix]

Actually, I don't think BA meant that sentence literally. Yes, powder position is paramount. The only way ignition can take place statistically the same way throughout the case is dependent on the ignition timing of each granule of powder in relation to its neighbor. The progression of pressure generated in total must be identical from shot to shot. Now, how can that be unless all those things mentioned by BA are not taken into account in a dramatic way? To play with the amount of powder in the case as the only variant means that every thing else must be held as a constant. That is what BA is saying to me in his post. ... felix

[Bass Ackward]

[QUOTE=Whitespider;298154]Wow Bass,
I can’t buy that. My testing was actually primer testing, I was looking for a primer that would minimize the effects of “powder position” in low density revolver loads. [QUOTE]


WS,

Not to get down on you, but there are physical limits. We all know that position sensitivity will result if we use less than a case full of a powder. If we have a need for 100% lack of it, then we must take steps to prevent it.

So there is a practical downside power limit for each cartridge. Powder position within that cartridge is paramount. So the minimum line should not be crossed unless you are prepared to go to a filler, drill out your flash holes, accept the limitations of that load (that you can't shoot straight up or down with that combo), seat deeper or go to a heavier bullet to fill case capacity, or .......... go to a case with a smaller case capacity.

I know, just like you, I have wanted to go beyond, but when you try that many powders, some with excellent histories for reduced loads over decades of use, can those all be wrong?

[Bass Ackward]

Got it! BA Rule 1 has been cited, all experimentation is impossible.
I'll stupidly continue, knowing that no results will have meaning.
BTW, the top post gives a clue as to where some answers may be found.
joe b.


Joe,

No I don't think you do. I am the biggest proponent of experimentation you will ever see. But there is only so much information that is transferable. Marshall has written his minimum stuff. You are finding different results with his favorite powders in his favorite cartridges. The point: He gave us his information that he shot for a lifetime. Did he ever claim that it was 100% position insensitive? So what good is adding my data going to be other than finding we have three variances? That will only prove that each person must do your own experimentation for minimums just as we all know we have to do for maximums.

Testing method was another variable I didn't list. IF I shoot single shot and only from a flat position, I have less of a problem than if I load a magazine full and want / need to shoot straight up and down. Big difference.

[Bass Ackward]

Wow Bass,
I can’t buy that. My testing was actually primer testing, I was looking for a primer that would minimize the effects of “powder position” in low density revolver loads. I used this procedure;

Test 1- I would fire 30 rounds over a chronograph, tipping the gun back (barrel up) to position the powder at the rear of the case before each shot, recording extreme spread and standard deviation (I was not interested in average velocity).

Test 2- I would fire 30 rounds over a chronograph, this time alternating tipping the gun back (barrel up) and tipping the gun forward (barrel down) before each shot, recording extreme spread and standard deviation.

I tested every primer I could get my hands on, with powders ranging from Bullseye to 2400 and projectiles cast and jacketed. In EVERY case, with EVERY powder/primer/projectile combination, test 2 showed significantly higher ESs and SDs. Some powder/primer/projectile combinations were much worse than others, but all showed enough difference that it couldn’t be statistical chance. In some cases the ES and/or SD would increase as much as 500%. Several of the tests that showed less than a 200% increase were run again, same results, so I quit running duplicate tests.


White Spider,

Sorry. Sometimes the best thing is to say nothing until your head clears.

My response before could have been summed up in one line: Position sensitivity is not a powder related phenom, but a case capacity one.

There. Instead of sounding insulting, that one line says it all. What you questioned was that I work my way down in powder charge using the hottest primer I have. Once I start to get position sensitivity, (at what ever level that occurs) game over. I must take another coarse of action to go lower. I hate those options so I change to a smaller cartridge.

I was NOT trying to say that a magnum primer solves all problems for everyone, but since I am lazy, it does for me if I can't seat deeper and fill the space with bullet.

[Larry Gibson]

Joe

I've run similar tests with several cartridges using fast and medium burning powders. The "data" you're collecting reflects pretty much the same as I found. I also included the ES as it paints a better picture of the vertical spread of the groups with the larger SD/ES at 100 yards. Also I think you're leaving out one important piece of "data"; that being the difference in mean point of impact of the groups caused by the different powder postions. I think you're on the right track just a couple other things to consider. Keep on with the tests, I find them interesting.

Larry Gibson