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.

[44man]

I don't know if you are doing it right by using Unique only. It is not known to be sensitive to position.
I think the only way to find out is by testing every fast powder in one gun first. I understand some are very sensitive. I have not seen much of a problem with Unique or 231.
I am anxious to see what you find with a larger case though. I have always used a pinch of dacron in a large case.
There is also the effect certain primers have on this too. So does every primer also need to be tested with each powder? Sounds like you have a LOT of shooting to do! :Fire:

[jonk]

Actually, I'd say it matters LESS with fast powders than with slow powders. For instance, try shooting a 45/70 with 4895. With all the powder forward or level, I get unburnt powder. With it all to the rear and held in by a wad or similar, I STILL get unburnt powder but less of it, and better accuracy.

[Hayfield]

I use three powders with my milsurps; 03 Springfield, SMLE 303 Brit and m39 Mosin Nagant so far to work up loads. H and IMR 4895 were both extremely position sensitive for me. To the tune of 200 fps or better. Unique was not and H4198 was not. I'm usually trying to acheive ~1600 fps with 200 gr bullets. Found out about the 4895 by accident while being lazy while reloading singles so I experimented a bit to make sure. Sho-nuff. Weird thing is I use much more 4895 (29.5 grs) in the case than Unique (12.5 grs) or 4198 (22.5 grs) so I thought there would be no effect. I was wrong in my assumption.