Wednesday, July 18, 2007
Pressure testing the .45 Colt Wildcat load (Clays/grits/200LRNFP)
The data on 8/24/07 (12 weeks after loading) indicates that the pressure for the Clays/grits load remains at a safe pressure as compared to the Magtech Cowboy 45-250 reference. Two values are shown for the reference. The Mp has the powder at the primer. The Mb has the powder at the bullet. The SASSwire data shows 20.5 K psi at 12 weeks. I'll test at 14 weeks to see if there's a continual slow degradation of the Clays/grits load as determined by an earlier test of ammo loaded for 18 months.
All loading manuals warn reloaders not to use fillers with smokeless powder. However, I learned that a couple of Clays/Grits loads were developed and continue to be used. The .45 Colt Wildcat (named by Coyote Cap) uses 3.8 grains of Clays, Quick Grits to the bell of the case, and a 200 grain LRNFP bullet. My personal load for the Wildcat used 3.6 grains of Clays. My presentation of test data is for information only and is not to be construed as a recommendation for use by anyone.
So, why use such a load? Well, most every CAS competitor will try to reduce loads in the .45 Colt and the result is lots of blowback in the revolvers (difficult cleaning) and particulate in the face in rifles like the Uberti 1873 replica. With the Clays/Grits load, there isn't any blowback!
A recent thread in the SASSwire indicated that this 3.8 grain Clays load was not safe because the pressure over time increased from about 10.5K psi to 24K psi over 14 weeks. The maximum SAAMI pressure for .45 Colt is 14K psi. The data presented in the thread indicated 14.5K psi at 6 weeks after reloading. At 8 weeks, the pressure was almost 17K psi. The Thompson Contender I use for testing will tolerate pressure far in excess of 30K psi. An Old Ruger Vaquero will tolerate similar pressure. Colt and clones will not!
I had quite a few Wildcat loaded with 3.6 grains of Clays/Grits and aged about 18 months. The brief testing I did indicated that the pressure was very low and likely the ammo had deteriorated.
My next objective was to try to duplicate the SASSwire thread data. I'm at 10 weeks and haven't been able to duplicate the SASSwire data.
The crude chart shows the SASSwire pressure points with a "J". The Magtech Cowboy 45-250 I use as a reference pressure are indicated with an "M". My Wildcat load used 4.0 grains of Clays to assure that the pressure (marked with a "JTB") would be higher than the original 3.8 grains. It's important to note that my data is presented in Oehler pressure units and the actual CUP or PSI is not known. The Magtech factory ammo is assumed to comply with SAAMI standards. As long as my Oehler test results show the Wildcat load to have less Oehler pressure units than the Magtech reference, I accept that the Wildcat load is less than the SAAMI maximum pressure for the cartridge. I'll try to clean up the chart later.
From the crude chart, you can see that the SASSwire data (marked with a J) increases over time such that one must conclude that the ammo is unsafe at 6 weeks after loading. Many cowboys left the playing field saying "I told you so!" But, the Fat Lady isn't finished singing yet.
For my test, every Wildcat pressure (marked with an JTB) test shows to be less than the Magtech Cowboy 45-250 (marked with a M). To date, the Wildcat pressure is certainly less than the SAAMI maximum. With the 7/18 and the 8/6 data, I was careful to position the Magtech Cowboy powder at the primer. This increases the reference pressure significantly. The pressure with the powder the bullet, reduces the results by 3K Oehler pressure units.
At this time, the reason for the change in pressure at each test day is unknown. This variation makes use of a reference load of critical importance. At least I think I have an understanding of why the reference load pressure was so variable.
I'll continue to update the chart over time as I have several hundred Wildcat cartridges reloaded. It's too early to say if the Wildcat load will increase over time. My suspicion is that the load will deteriorate over time. I'll repeat the tests at a later date and include velocity measurements.
As a final comment, I have used .45 Autorim with 2.7 grains of Clays and grits to the bell under a 160 grain LRNFP bullet in my Ruger Vaqueros for several years in both practice and CAS matches. I tested Cowboy .45 Special ammo with the .45 Autorim and found the pressure to be less than the Magtech reference ammo over time. The Cowboy .45 Special brass is identical in every respect to the .45 Autorim excepting the rim.
In my '73 lever rifle, I use a modification of the Wildcat load (.45 Colt brass) by using the 160 grain LRNFP rather than the 200 grain LRNFP bullet and kept the 3.6 grains of Clays with grits to the bell. The pressure has never reached the offset of 7000 psi for .45 Colt brass.
More later . . .