Look for some advice. I have been reloading 7mm STW for about a year. I want to experiment with other powders that do not have printed load information for this caliber. When I select a new powder to experiment with how do I determine where to begin on the gains of power? I am looking for two answers from the community here: Simple straight forward answer and the technical answer.
Developing Your Load Data
- Thread starter barrybrice
- Start date
This is only my opinion, and not meant to offend anyone.
STOP AND FORGET ABOUT IT!
If there is no load data for a specific powder, there is probably a very good reason for it!
There are at least 10 different powders listed in my manual for the 7mmSTW. If there were more powders that were acceptable for use, there would likely be data for them. Unless you have equipment to measure the pressure of the rounds when fired, this is a very bad idea and can end up with catastrophic results very easily.
Experimenting is best left to the guys in the lab with degrees and equipment to measure pressure.
If you have QuickLoad, you may be able to run some other powders through the progream and see what you come up with. But unless you have a device to measure pressure, the actual testing can be very dangerous. Some powders can have serious pressure spikes with very little additional powder when used in a case of improper size.
Bottom line, unless you have done this before and have the equipment necessary to provide scientific data, this is best left to an expert. If you need instructions on how to start, it's best left alone.
Experimenting with a potential bomb is the quickest way to find the ER or a good funeral home, especially if you don't have the proper knowledge or equipment.
STOP AND FORGET ABOUT IT!
If there is no load data for a specific powder, there is probably a very good reason for it!
There are at least 10 different powders listed in my manual for the 7mmSTW. If there were more powders that were acceptable for use, there would likely be data for them. Unless you have equipment to measure the pressure of the rounds when fired, this is a very bad idea and can end up with catastrophic results very easily.
Experimenting is best left to the guys in the lab with degrees and equipment to measure pressure.
If you have QuickLoad, you may be able to run some other powders through the progream and see what you come up with. But unless you have a device to measure pressure, the actual testing can be very dangerous. Some powders can have serious pressure spikes with very little additional powder when used in a case of improper size.
Bottom line, unless you have done this before and have the equipment necessary to provide scientific data, this is best left to an expert. If you need instructions on how to start, it's best left alone.
Experimenting with a potential bomb is the quickest way to find the ER or a good funeral home, especially if you don't have the proper knowledge or equipment.
I guess I would tend to be a little more brave (or foolish!). The first thing I check when comparing cartridges in a particular bore is the case volume. It is the single most important factor in determining how much and what type of powder will work. This site has a number of cartridges listed, and also shows you how to measure it using water and a fired, unsized case. The 7 STW is unfortunately not listed, so you may want to measure it, so you can compare to other 7MM cases such as the RUM. It also shows a way to calculate pressures, but I'm not up for that.
http://kwk.us/cases.html
This is the cartridge size I see for the 7 STW.
http://stevespages.com/jpg/cd7stw.jpg
This is the cartridge diagram for a 7 RUM.
http://stevespages.com/jpg/cd7remingtonultramagnum.jpg
Check the dimensions for yourself to confirm, but I would suggest the STW is just slightly under the RUM for capacity, due to the RUM having a slightly larger diameter at the shoulder, and a steeper shoulder. The rest of the dimensions seem to be just normal tolerance differences.
So, if it were me, I would check for loads for the RUM, and work up from the minimums, and not expect to get to the maximums.
The other factor is your gun and what pressure it can handle. You need to convince yourself that your gun is as able to handle the pressures as the RUM.
http://kwk.us/cases.html
This is the cartridge size I see for the 7 STW.
http://stevespages.com/jpg/cd7stw.jpg
This is the cartridge diagram for a 7 RUM.
http://stevespages.com/jpg/cd7remingtonultramagnum.jpg
Check the dimensions for yourself to confirm, but I would suggest the STW is just slightly under the RUM for capacity, due to the RUM having a slightly larger diameter at the shoulder, and a steeper shoulder. The rest of the dimensions seem to be just normal tolerance differences.
So, if it were me, I would check for loads for the RUM, and work up from the minimums, and not expect to get to the maximums.
The other factor is your gun and what pressure it can handle. You need to convince yourself that your gun is as able to handle the pressures as the RUM.
Preacher said:
Thanks Preacher. I have been loading for a bit over 10 years now, and don't plan on trying to develop my own load data for new powders any time soon.
I had enough luck to walk away from an rifle exploding beside me last summer due to someone using a powder unsuited to the round he was shooting. That was enough for me.
To anyone foolish enough to try it without the proper knowledge or equipment, it's your life, go for it. Just be sure to tell others around you that you might have a potential bomb in your hands and to stand back. I wasn't given that courtesy, and nearly had my face taken off because of it.
And if you need to ask how to go about it, you don't have the proper knowledge to attempt this.
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