Powder Position Sensitivity

[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 are and will be on http://sports.groups.yahoo.com/group/CB-BOOK/ in FILES,in ERRATA

AVERAGE VELOCITY
DATE CALIBER POWDER GRAINS POWDER FRONT POWDER LEVEL POWDER REAR DACRON WAD
2/6/2008 30/30 Unique 7.0 1,195 1214 1185
4/9/2008 30/30 Unique 7.0 1163 1175
2/20/2008 30/30 Unique 8.5 1346 1365 1378
4/9/2008 30/30 Unique 8.5 1337 1368
2/20/2008 30/30 Unique 10.0 1502 1519 1498
4/9/2008 30/30 Unique 10.0 1491 1478
2/27/2008 45/70 Unique 14.0 1195 1240

2/27/2008 45/70 SR4759 22.0 1128 1310

3/12/2008 30/30 IMR4227 14.5 1353 1347 1435
3/12/2008 30/30 IMR4227 14.5 1357 1357 1454 Rem 2 1/2
3/26/2008 30/30 IMR4227 14.5 1457
4/9/2008 30/30 IMR4227 14.5 1392 1451

3/26/2008 30/30 IMR4198 18.5 1614 1629 1650

STANDARD DEVIATION OF VELOCITY
DATE CALIBER POWDER GRAINS POWDER FRONT POWDER LEVEL POWDER REAR DACRON WAD
2/6/2008 30/30 Unique 7.0 28.1 39.3 14.3
4/9/2008 30/30 Unique 7.0 17.8 19.8
2/20/2008 30/30 Unique 8.5 16.1 18.8 29.5
4/9/2008 30/30 Unique 8.5 16.6 29.3
2/20/2008 30/30 Unique 10.0 28.8 22.3 19.5
4/9/2008 30/30 Unique 10.0 46.0 11.3
2/27/2008 45/70 Unique 14.0 28.0 15.8


2/27/2008 45/70 SR4759 22.0 35.5 31.8

3/12/2008 30/30 IMR4227 14.5 19.0 17.7 14.3
3/12/2008 30/30 IMR4227 14.5 30.4 25.5 22.7 Rem 2 1/2
3/26/2008 30/30 IMR4227 14.5 24.3
4/9/2008 30/30 IMR4227 14.5 26.1 20.6

3/26/2008 30/30 IMR4198 18.5 32.3 24.4 30.9


iT WOULD CERTAINLY HELP IF SOMEBODY COULD MAKE A word document print here. Anybody??
joe b.

[runfiverun]

joe b. i can't do it but i'm sure at least one of the guy's here can
thank's for sharing your test info

[44man]

I use dacron in my 45-70 revolver with 4759. I don't suggest tamping it down, leaving an air space above it. Put it in so the base of the boolit pushes it down some. That might mean a larger tuft of dacron.
I use lighter boolits and can use more powder so that I don't have a lot of space above the powder, that helps too.

[Three44s]

+1 What 44man said!!!

Do not tamp down those wads!

A recipe for a bulged chamber!

I think that ALL powders are position sensitive ........ but by degree.

Take Titegroup ........ it's touted as "position insensitive" ........... I find it to be "less sensitive".

What I do for better powder burn is to inside flash hole debur.

I found this sort of by accident.

I first used this on a varmint rifle ........ later I was using some old RedDot up (notoriously dirty in about everything but a real hummer in shotgun) ...... but I was using it in .38 cases.

Well after doing the flash holes ....... it acted like a different powder (as to cleanliness).

Before it was overwith ....... I deburred ALL of my metalic cases ..... for all calibers, rifle and handgun alike ........ AND swear by it.

Three 44s

[joeb33050]

I've been tamping Dacron wads down on the powder for 1.47 zillion rounds, over 30+ years, and never4, repeat, never a ringed chamber.
joe b.

[Larry Gibson]

Joe b

I use dacron as a filler instead of a wad. It is not out of fear of a ringed chamber. I like you did it for years with no sign of a problem. I also think if there was an abnormality with doing so it would have shown as an anomoly in chronograph radings which it did not. I only use it as a filler because most of my loads using dacron are in medium to high power loads. These generate recoil. The wads would break loose from recoil in the rounds in the magazine (usually the last couple in the magazine) and powder migrates around, in and through the wad causing hangfires. That's the only reason. For those who want to single load the dacron as a wad works very well as you've demonstrated. Well done test by the way.

Larry Gibson