Powder Position

[chuebner]

Does anyone know if there is any reference material published that gives powder position sensitivity by powder brand (Accurate, Alliant, etc)? I have read conflicting articles about powder position and the use of fillers to keep the powder against the primer. If possible I would like to eliminate an extra reloading step. Currently I am using Unique, 2400, Reloader 7 and IMR4198 for 1450-1650 fps. loads in my 03A3 and K31. Any help appreciated.

Charlie

[Dale53]

Charlie;
ALL powders are subject to position sensitivity-some just more so than others. If you have access to a chronograph, you can easily determine whether a particular powder and charge are a problem. Hold the rifle so as to position the powder over the primer for one series of shots (recording everything, of course). Then hold the rifle so that the powder is postitioned next to the bullet and chronograph that series. Compare the two and decide if the difference in velocity is meaningful or not. By doing it yourself, you determine what is happening with YOUR equipment and loading techniques, not what happened with someone else's with different primers, differing bullet sizes, differing alloys, etc.

The farther you shoot, the more the difference in velocity will effect your verticals. You might have no problems at 100 yards but lots at 300-500 yards. You will have to decide.

A generalization might be to say that whichever powder gives you the velocity that you desire within the pressure range you need and is the BULKIEST is the powder to try first. 4759 was specifically designed to have large "fluffy" grains to bulk up when replacing black powder loads to minimize the need for fillers. The only problem most people have with 4759 is that it doesn't measure well in some measures.

Dale53

[Frank46]

Charlie, according to some folks 4759 is position sensitive, but based on my results with the 7.62x54R cartridge i would say its not, but then what do I know?.
Both 4895 and 4064 are position sensitive. There were some tests done with 4895 that proved this. And 4064 in a 308 win rifle I own gave 100 fps different velocity readings over a ten shot string. Could not figger out what was what until I chronographed the load. Always wondered why I'd get either high or low shots in the group. So had to abandon the use of 4064 in my 308. But 4895 always shot well for me. I thinkit has to do with the charge and the position of the powder in regards to the primer and the bullet. If close to the primer then you would (working from memory here CRS) yoou would get a high reading, if powder was close to the base of the bullet then the reading would be lower. If I remember the velocity difference was on the order of approximately 100 fps or so.
Frank

[Bass Ackward]

Charlie,

Three big factors that affect burning are case design, powder type, and charge level.

How many times have you heard that ball powders are cooler burning and harder to ignite than stick powders. OK. Pop quiz: Which type of powder do you think would tend to have more position sensitivity with a reduced charge?

Picture in your mind a tapered case and a straight sided case. Powder positioning in tapered cases sorta happens for ya on the level if you don't have a filler. Thus the success of the 30-06 on the range with cast bullets. If you have a straight sided case then it is free to move anywhere between points A & B and you have to be more sensitive to positioning. Obviously these are not blanket statements because you can have a short, straight sided case and a long, tapered one. To compensate, we have the short mag concept. This is just to get you thinking.

Look how long it took to get burn rate charts from the powder companies. And still you will find no two the same. Powders burn differently at different pressure levels. 2400 is a slow powder in a 38 Special. 2400 is an ultra fast in a 7mm Mag.

So any powder can be position sensitive under the right conditions. And this is also why the biggest variance you will see on this board is the topic of fillers. So we don't have that quite .... nailed down yet.

[Bucks Owin]

IMHO, SR-4759 has enough bulk to be position "insensitive" in most cases. Generally there's not much in the way of airspace under the boolit. (At least in .44 mag loadings where I use it)

FWIW,

Dennis