Saturday, January 15, 2011

Update: 145 SWC Testing & 200 SWC Testing

I ran into a delay (besides the weather, which closed the range for days) due to a casting problem.  Based on early results I expected this boolit to be very accurate and group less than 1 inch.  As testing proceeded I could only get 1.2 inch groups.

Rather than blame the mould, I started reviewing the process, what may have changed and also started measuring the boolits more closely.  I discovered that for some reason they were slightly undersized.

The root cause: A new casting pot from Lee heats hotter than my old one.  This increase in alloy temp also heated the mould too much.  This is my fault for not double checking everything with a new bottom/pour furnace from Lee.

With alloy that was already hot, it heated the mould too much as well.  With the mould preheated on a hotplate, look at the graph of the boolit size as the mould is overheated (no frosting though).  As usual, click on the graph to see it full size:

The graphs shows the boolit diameter in sequence as 9 boolits were cast.  They start good and fall off as the heat builds.

Monitor the affect of alloy temperature and mould temperature on your diameters.  It has to be hot, but don't get to hot and end up with undersized boolits.  They just aren't as accurate.

The upside is that the only tests affected are the 145 SWC and early 200 SWC.  I have a great solution planned and once implemented and verified I’ll post it.  It's much more than just turning the pot down.  I want accuracy so it needs to be consistent.

Upcoming posts for additional accuracy tests:
  • Results using H110 magnum powder will be coming in the next few weeks. 
  • In the works is (already started for that matter) tracking the shrinkage of 357 boolits as they age.  When pursuing the best accuracy possible, it all makes a difference.  Especially for that event or day at the range when you want your “best of the best” loaded in the cylinder
  • Oh, also coming is test results with a new-to-me Dan Wesson with a 6 inch and 2 inch barrel.  It has a different twist rate than the Taurus, more coming about that…  First I’ve gotta get all the lead out of the new revolver.  Enough has been removed to cast a 145 boolit, and there’s more!  My wonderful wife came to me on my birthday and said she’d like to buy me a gun.  Wow, I found the Dan Wesson and bought it.  After sitting at UPS for days due to icy roads it finally showed up at the Range/FFL.  It’s a Monson made model 15-2, what a nice trigger. 
  • Ummm, there is that custom mould too.  Those results are a month or so out as the custom sizing die (for just $34) is needed as well.
  • Did I mention my wonderful wife.  She puts up with all this and enjoy going to the range every so often too.  I really enjoy those range trips.

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