Powder Position

[joeb33050]

POWDER POSITION SENSITIVITY TESTING

Does the position of the powder in the cartridge case affect muzzle velocity, (MV) and/or the standard deviation, (STDEV) of MV?
I had tested the sensitivity of a powder by testing for increased accuracy with a minimum sized Dacron wad tamped down on the powder; and concluded that, for example, SR4759 and Unique are position sensitive in the 45/70 and IMR4227 is not position sensitive in the 32/40 and 30/30.
The testing conditions were expanded when I realized that my definition and test conditions were not complete (or correct); this epiphany occured after a lot of testing.

TESTING CONDITIONS
POWDER FRONT-hold the rifle with cartridge chambered at ~ a 45 degree angle down and slap the side of the rifle three times, then put it carefully on the rest.
POWDER LEVEL-put the rifle with cartridge chambered on the rest and slap the side of the rifle ten times.
POWDER REAR-hold the rifle with cartridge chambered at ~ a 45 degree or greater angle up and slap the side of the rifle three times, then put it carefully on the rest.
DACRON WAD-I recommend cotton but use Dacron wads. I use as small a wad as possible, a teased wad about dime to penny size, tamped down on top of the powder with a pencil.
I try to chronograph a minimum of 15 of each condition, shooting at 100 yards over my PACT chronograph.
Il 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

TEST RESULTS
IMR4227 was tested on 3/12/08 with a test with the powder at the rear on 3/26/08. The bullets used on 3/26 were slightly harder and lighter than the 3/12 bullets.
IMR4227, 14.5 GRAINS, 30/30, WLP PRIMERS
DATE 3/12/08 3/12/08 3/26/08 3/12/08
POSITION POWDER POWDER POWDER DACRON
FRONT LEVEL REAR WAD
MV AVG. 1353 1347 1457 1435
MV S. D. 19.0 17.5 24.3 14.3

IMR4198, 18.5 GRAINS, 30/30
DATE 3/12/08 3/12/08 3/26/08
POSITION POWDER POWDER POWDER
FRONT LEVEL REAR
MV AVG. 1614 1629 1650
MV S. D. 32.3 24.4 30.9

UNIQUE, 7.0 GRAINS, 30/30
DATE 2/6/08 2/6/08 2/6/08
POSITION POWDER POWDER POWDER DACRON
FRONT LEVEL REAR WAD
MV AVG. 1195 1214 1185
MV S. D. 28.1 39.3 14.3

UNIQUE, 8.5 GRAINS, 30/30
DATE 2/20/08 2/20/08 2/20/08
POSITION POWDER POWDER POWDER DACRON
FRONT LEVEL REAR WAD
MV AVG. 1346 1365 1378
MV S. D. 16.1 18.8 29.5

UNIQUE, 10.0 GRAINS, 30/30
DATE 2/20/08 2/20/08 2/20/08
POSITION POWDER POWDER POWDER DACRON
FRONT LEVEL REAR WAD
MV AVG. 1502 1519 1498
MV S. D. 28.8 22.3 19.5

UNIQUE, 14.0 GRAINS, 45/70
DATE 2/27/08 2/20/08
POSITION POWDER POWDER POWDER DACRON
FRONT LEVEL REAR WAD
MV AVG. 1195 1240
MV S. D. 28.0 15.8

SR4759, 22.0 GRAINS, 45/70
DATE 2/27/08 2/27/08
POSITION POWDER POWDER POWDER DACRON
FRONT LEVEL REAR WAD
MV AVG. 1128 1310
MV S. D. 35.5 31.8

IMR4227, 14.5 GRAINS, 30/30,REMINGTON 2 1/2 PRIMERS
DATE 3/12/08 3/12/08 3/12/08
POSITION POWDER POWDER POWDER DACRON
FRONT LEVEL REAR WAD
MV AVG. 1357 1357 1434
MV S. D. 30.4 35.5 22.7

[runfiverun]

joe
i have been following your posts
and have made a fewobservations [kept to myself]
and waiting for an overview, and conclusion, with your observations
based on your notes.

the numbers wont lie and could be very helpful

[Larry Gibson]

Joe

Are you going to offer any conclusions or observation on your test?

Larry Gibson

[joeb33050]

Joe

Are you going to offer any conclusions or observation on your test?

Larry Gibson

My first observation is that I can't get the post to print correctly here. It doesn't show the data correctly, hence it can't be read. Do you know how to fix this?

Another thought is that I'm still thinking that the "real" test of position sensitivity is with and without the Dacron wad. Some write about holding the rifle up to move the powder back, but this is, I think, not as good as the Dacron.

I'm going to fill in the blanks on the powders tested, and try that 5744 powder and maybe Blue Dot. Don't know what other powders to try.

joe b.

[44man]

In my opinion, anytime there is any kind of an air space above ANY powder, there will be a difference as to where the powder is located. Some more and some less but there is no way to prevent it other then a pinch of dacron.
I find 4759 is not real bad in my 45-70 BFR without a filler but I do get a little better accuracy with dacron so it is worth doing.
It is an interesting experiment to test all the powders to find which one is the least sensitive but I don't think there is one that is perfect.
Maybe cordite! :mrgreen:

[Larry Gibson]

My first observation is that I can't get the post to print correctly here. It doesn't show the data correctly, hence it can't be read. Do you know how to fix this?

Another thought is that I'm still thinking that the "real" test of position sensitivity is with and without the Dacron wad. Some write about holding the rifle up to move the powder back, but this is, I think, not as good as the Dacron.

I'm going to fill in the blanks on the powders tested, and try that 5744 powder and maybe Blue Dot. Don't know what other powders to try.

joe b.

I don't know how you are laying out the info before posting so I'm not sure how to help. You might try another way and post on the test site to see.

I did quite a bit of testing on this also over the years. My findings basically were (keep in mind there were exceptions) that will most powders the only time powder position really effected anything accuracy wise was when shooting at extreme angle up or down. The chronograph confirmed this through much higher velocity or much lower velocity. Strangely, depending on the cartridge and powder, sometimes the velocity was much faster when shooting up and sometimes it was much slower and the same when shooting down. I could get consistent results with one powder but not with all powders in all cartridges.

It was my testing of such loads (in rifle cases with capacity greater than a .222 Rem) that led me to this method;
* First, with all powders the load must be such that the powder is burning consistently giving good internal ballistics (close ES and SD on chronograph) at the velocity desired. Many "fast burning" powders do not burn consistently at these lower velocity/pressures, especially with light for caliber bullets.

*In lower velocity loads (300 - 1400 fps) I use either Bullseye or Unique with no wad or filler. These two powders, in 95% of the shooting, have shown that powder position is not a factor with accuracy when normally gun handling is used.

*In mid to HV range (1500-2400 fps) with light medium weight for caliber bullets I use the "slower" of the fast burning powders; 4759, 4198, 4227, 5744 and 2400. These are also used with no wad or filler. Again the powder must be in a correct pressure range to burn efficiently. Sometimes this means too high a velocity for a particular bullet. A slightly faster burning powder is used until a satisfactory load is found.

*With medium to heavy for caliber bullets I like to use a medium burning powder; 4895, 3031, RL7, etc. for velocities of 1700-2200 fps. These usually give a 60-80% loading density and I most often use a dacron filler with these to improve internal ballistics (doesn't always work though).

*In larger cases the slow burning powders; 4831, 4350, RL19, RL22, etc. provide good velocity with the heavy bullets for caliber. Loading density is 90-100%. changing powders will provide changes in velocity and internal consistency.

*For HV loads I find my best success comes when using the slowest burning powder that gives close to 100% loading density at the desired velocity levels while giving good internal consistency also.

These are not hard and fast guidelines as some cartridge/bullet combinations require a combination of each. However I'd say that 95% of my loads generally fall with in one of these guidelines.

I am very interested in seeing more of your experiment(s).

Larry Gibson

[runfiverun]

larry
you keep putting out information like this and we are going to have to have
a gibson forum.
well maybe two one to read and one to argue with larry.

hahahahahaha

[Buckshot]

..............There was an article written in "Handloader" magazine a couple years back by Dave Scovill I believe it was. He was using pistol cartridges. He showed what most would assume to be the truth, and that is that there is NOT one powder that is not position sensitive, even in pistol cases. However there ARE powders that are less position sensitive then others.

He used several powders in several pistol cases and found that of those powders tested, W231 was the least affected by it's position in the case. However, it WAS affected as position did create an effect in accuracy and ballistics.

................Buckshot