offshore44
04-30-2014, 02:56 PM
I ordered my first bunch of WC860 a few days ago and wanted to make sure that I understood the mechanics and theory of working up loads with it. I hope to restrict the discussion to cast boolits.
Here's what I think I understand so far (from my loading journal):
Reloading using 50 BMG surplus military powders.
It is possible to reload cartridges other than the "Big 50" with military surplus 50 BMG (and 20mm cannon) powder. These powders are: WC860, WC867 and WC872. This is an advanced reloading technique, and should not be attempted unless you are comfortable with reading pressure signs, can read a powder burn rate chart, have a strong rifle and quality brass.
Cartridges as small as the .223 have been successfully loaded using this technique. It is most applicable to rifle cartridges that are "over bore" like the 7mm Rem Mag (see 300 win mag note). It works fine with the 300 Win Mag (start with no kicker charge and a hot magnum primer) and cartridges like the 45-70, 458 Win Mag and other straight wall cartridges. You can usually find a good load for cartridges like the 308, 30-06 7x57 and such. It will cycle the action in gas operated semi-autos like the FAL and M1A1. It will work to some degree with jacketed and cast bullets. It will generate velocities that range from black powder levels to starting load levels.
The background on this technique comes from shooting the large black powder cartridges with black powder. One of the issues with black powder is the powder residue that is left in the barrel. Attempts were made to clean up the burn by using small charges of smokeless powder under the main black powder charge to clean up the burn. The technique is called "Duplexing", and is fairly well accepted. It also has a long history.
The theory: Is it possible to use a full case charge of extremely slow, by civilian standards, powder to propel a bullet out of a rifle at close to normal velocities. What we are attempting to do is replicate the burn conditions at ignition inside of a smaller case using a smaller primer that occur inside of a 50BMG case. The thing we need to do is raise the temperature and the pressure at ignition so that it matches closely enough the temperatures and pressures of a 50BMG at ignition that these slow powders will burn completely and cleanly.
To start: All of the cases should be in good condition. The bullets should be in the medium to heavy weight range for the cartridge. The rifle must be strong and in good condition. Quality reloading tools should be used to include scales, micrometers, calipers, chronographs & etc.
Select the cartridge and bullet to be used. Make up a dummy round that fits the rifle. This will set your cartridge over all length. Measure and find the base of the bullet at this COL. Fill the case with the 50BMG powder to this line. Weigh that charge. Do this several times until you are confident that you have found your case capacity for this powder, case and boolit combination. We are looking for very slight compression on the powder charge (1/16" or so) so add a 1/2 grain of powder at a time until this compression is achieved. This is the starting charge to begin your load development. Shoot your test rounds to see what happens. For duplexing, we need slight compression to keep the kicker charge from mixing with the main powder charge during normal handling. Select a medium to fast stick rifle powder (pistol / shotgun powder?) to use as a kicker charge. H4895 is a pretty good place to start. DO NOT use ball powders, flake powders may be used after you gain experience with this technique. Never, under any circumstances, use a powder that exhibits a change in burning rate when compressed. Trail Boss is a classic example. Don't do it. Bad things happen. Prepare your cases and bullets as you would for your normal loading procedure. Use a standard rifle primer. Make up a small selection of about 5-10 rounds to start. Put 3 grains (?) of your fast to medium rifle powder (?) in the case. Reduce the 50 BMG charge by 3 grns to compensate. USE A SCALE! Gently add the 50BMG powder to the case and immediately seat the bullet and provide a firm crimp. These are to be loaded completely one at a time. Double charging your kicker powder will lead to a catastrophic event. If not now, then later. Make sure!
Go out and shoot these. Check carefully for overpressure signs. Check the primer for flattening and cratering. Check the case head for ballooning. Make sure the extraction feels normal. Check the bore for unburned kernels of powder. There may be a few, that is OK and to be expected. If there is no unburned powder in the bore and none out in front of the muzzle, you may be good to go. If you do find unburned powder reload 5-10 more rounds with 0.1 grain additional kicker powder. Reduce the 50BMG powder by 0.1 grain to compensate. Repeat this process until the 50BMG powder burns cleanly and no powder is ejected unburnt from the muzzle OR pressure signs start to show up. If pressure signs show up before the 50BMG powder is burning cleanly, then you need to go to a faster (slower? higher nitro content?) stick rifle powder as a kicker charge. We are looking for the balance of temp and pressure that mimics the conditions of ignition in a 50BMG case, remember? These loads can be modified as required after the clean burn point is found to obtain extremely low velocity spreads and standard deviations. Using the standard ladder load test will usually find a sweet spot where barrel harmonics, kicker charge load and bullet weight will allow you to load these almost like a normal load. When you find that load, you have achieved nirvana! Keep good records, on paper.
These loads are safe once correctly worked up in the gun they were worked up in, the powder lots that were used in the work up, brass and the bullet weight and type used in the workup. If you change any single component, work up these loads again from scratch. Even something as small as a change in primer lots will affect these loads sometimes. Don't swap loads between rifles of the same caliber.
Again, these loads are proven safe and effective, but you have to follow the rules or things don't work out well sometimes. Rarely, but sometimes. Don't be THAT guy.
A few notes: These powders burn cool compared to civilian powders. They are easy on a barrel and most especially easy on chamber throats. 50BMG surplus powders are cheap compared to regular powders, especially when bought in bulk. I have seen 20mm cannon powder sold for $45 for an eight pound keg recently, with no HazMat fee if you buy six kegs. That's bloody cheap in anybodies book. 50BMG powder is in the $60 for eight pound range, and is preferable. When you buy this powder, get as much as you can afford so that you don't have to go through the workup again. Mil-surp powders vary in burn rate from lot to lot, so getting a bunch at one time cuts down on the hassle factor. A new workup is mandatory if you get a lot # that is different that the original. Write the lot numbers down and keep track of such things. These are low pressure rounds, the kicker charge is what generates the pressure to start, and gets the whole thing working the way it's supposed to. The kicker powder can be most any stick fast to medium burn range rifle powder. Some folks have had good success with slow flake shotgun and pistol powders as well. In this day and age, you have to use what's available sometimes. Just be aware of what you are doing and load accordingly.
Comments and corrections are desired and encouraged! I would really like to make sure I understand the theory and mechanics of this before I jump off into burning a bunch of this stuff...
Thanks a bunch!
Here's what I think I understand so far (from my loading journal):
Reloading using 50 BMG surplus military powders.
It is possible to reload cartridges other than the "Big 50" with military surplus 50 BMG (and 20mm cannon) powder. These powders are: WC860, WC867 and WC872. This is an advanced reloading technique, and should not be attempted unless you are comfortable with reading pressure signs, can read a powder burn rate chart, have a strong rifle and quality brass.
Cartridges as small as the .223 have been successfully loaded using this technique. It is most applicable to rifle cartridges that are "over bore" like the 7mm Rem Mag (see 300 win mag note). It works fine with the 300 Win Mag (start with no kicker charge and a hot magnum primer) and cartridges like the 45-70, 458 Win Mag and other straight wall cartridges. You can usually find a good load for cartridges like the 308, 30-06 7x57 and such. It will cycle the action in gas operated semi-autos like the FAL and M1A1. It will work to some degree with jacketed and cast bullets. It will generate velocities that range from black powder levels to starting load levels.
The background on this technique comes from shooting the large black powder cartridges with black powder. One of the issues with black powder is the powder residue that is left in the barrel. Attempts were made to clean up the burn by using small charges of smokeless powder under the main black powder charge to clean up the burn. The technique is called "Duplexing", and is fairly well accepted. It also has a long history.
The theory: Is it possible to use a full case charge of extremely slow, by civilian standards, powder to propel a bullet out of a rifle at close to normal velocities. What we are attempting to do is replicate the burn conditions at ignition inside of a smaller case using a smaller primer that occur inside of a 50BMG case. The thing we need to do is raise the temperature and the pressure at ignition so that it matches closely enough the temperatures and pressures of a 50BMG at ignition that these slow powders will burn completely and cleanly.
To start: All of the cases should be in good condition. The bullets should be in the medium to heavy weight range for the cartridge. The rifle must be strong and in good condition. Quality reloading tools should be used to include scales, micrometers, calipers, chronographs & etc.
Select the cartridge and bullet to be used. Make up a dummy round that fits the rifle. This will set your cartridge over all length. Measure and find the base of the bullet at this COL. Fill the case with the 50BMG powder to this line. Weigh that charge. Do this several times until you are confident that you have found your case capacity for this powder, case and boolit combination. We are looking for very slight compression on the powder charge (1/16" or so) so add a 1/2 grain of powder at a time until this compression is achieved. This is the starting charge to begin your load development. Shoot your test rounds to see what happens. For duplexing, we need slight compression to keep the kicker charge from mixing with the main powder charge during normal handling. Select a medium to fast stick rifle powder (pistol / shotgun powder?) to use as a kicker charge. H4895 is a pretty good place to start. DO NOT use ball powders, flake powders may be used after you gain experience with this technique. Never, under any circumstances, use a powder that exhibits a change in burning rate when compressed. Trail Boss is a classic example. Don't do it. Bad things happen. Prepare your cases and bullets as you would for your normal loading procedure. Use a standard rifle primer. Make up a small selection of about 5-10 rounds to start. Put 3 grains (?) of your fast to medium rifle powder (?) in the case. Reduce the 50 BMG charge by 3 grns to compensate. USE A SCALE! Gently add the 50BMG powder to the case and immediately seat the bullet and provide a firm crimp. These are to be loaded completely one at a time. Double charging your kicker powder will lead to a catastrophic event. If not now, then later. Make sure!
Go out and shoot these. Check carefully for overpressure signs. Check the primer for flattening and cratering. Check the case head for ballooning. Make sure the extraction feels normal. Check the bore for unburned kernels of powder. There may be a few, that is OK and to be expected. If there is no unburned powder in the bore and none out in front of the muzzle, you may be good to go. If you do find unburned powder reload 5-10 more rounds with 0.1 grain additional kicker powder. Reduce the 50BMG powder by 0.1 grain to compensate. Repeat this process until the 50BMG powder burns cleanly and no powder is ejected unburnt from the muzzle OR pressure signs start to show up. If pressure signs show up before the 50BMG powder is burning cleanly, then you need to go to a faster (slower? higher nitro content?) stick rifle powder as a kicker charge. We are looking for the balance of temp and pressure that mimics the conditions of ignition in a 50BMG case, remember? These loads can be modified as required after the clean burn point is found to obtain extremely low velocity spreads and standard deviations. Using the standard ladder load test will usually find a sweet spot where barrel harmonics, kicker charge load and bullet weight will allow you to load these almost like a normal load. When you find that load, you have achieved nirvana! Keep good records, on paper.
These loads are safe once correctly worked up in the gun they were worked up in, the powder lots that were used in the work up, brass and the bullet weight and type used in the workup. If you change any single component, work up these loads again from scratch. Even something as small as a change in primer lots will affect these loads sometimes. Don't swap loads between rifles of the same caliber.
Again, these loads are proven safe and effective, but you have to follow the rules or things don't work out well sometimes. Rarely, but sometimes. Don't be THAT guy.
A few notes: These powders burn cool compared to civilian powders. They are easy on a barrel and most especially easy on chamber throats. 50BMG surplus powders are cheap compared to regular powders, especially when bought in bulk. I have seen 20mm cannon powder sold for $45 for an eight pound keg recently, with no HazMat fee if you buy six kegs. That's bloody cheap in anybodies book. 50BMG powder is in the $60 for eight pound range, and is preferable. When you buy this powder, get as much as you can afford so that you don't have to go through the workup again. Mil-surp powders vary in burn rate from lot to lot, so getting a bunch at one time cuts down on the hassle factor. A new workup is mandatory if you get a lot # that is different that the original. Write the lot numbers down and keep track of such things. These are low pressure rounds, the kicker charge is what generates the pressure to start, and gets the whole thing working the way it's supposed to. The kicker powder can be most any stick fast to medium burn range rifle powder. Some folks have had good success with slow flake shotgun and pistol powders as well. In this day and age, you have to use what's available sometimes. Just be aware of what you are doing and load accordingly.
Comments and corrections are desired and encouraged! I would really like to make sure I understand the theory and mechanics of this before I jump off into burning a bunch of this stuff...
Thanks a bunch!