Sunday, July 24, 2011

Part 1: Using The Ladder Test - Incremental Load Development Method To Work Up Loads For A Ruger Blackhawk

This is part 1 of a multipart series.  Over a period of weeks there will be follow-on posts with additional information.

In the past I enjoyed shooting the Taurus 66, putting thousands of cast hand-loaded rounds through it.  Now I'm working out the same loads with a Ruger Blackhawk, 357 Magnum.   It's an older three-screw, 6 1/2 inch barreled gem of a revolver.  The plan is to rehash the best loads and see what works best in this new-to-me revolver.

We know the most accurate bullet designs, and have proven loads to work with.  However I've decided to use a Ladder Test.  This is a great way to quickly validate the best loads, and to also work out some new powder-bullet combination's.  See the "Most Accurate Bullet Moulds and Loads Table" at the top of the right-hand column for a complete listing.

I'll start with the Lee TL358-158-SWC that has already been lapped.  It drops full sized bullets with a .3604 diameter, that weigh 166 grains (I'll refer to them as 168's).  They will be sized to .360 using a custom Lee push through sizer and lubed with Johnson's Paste Wax and Alox.

The plan is to use three powders.  Two of them have demonstrated incredible accuracy.
  1. 700X being a fast burn-rate powder
  2. H110 being the most accurate magnum powder tested to date, and I don't have a magnum load for this bullet, yet
  3. The last is Unique, it's a great powder that gets loaded more than any others, by more handloaders across the county than any others.  It's generally accepted to be be the most flexible handgun powder since it's inception many years ago.

Now that the stage is set, what the heck is the Ladder Test - Incremental Load Development Method.  For a great read, click on that link.  It will download a PDF article written by Randolph Constantine.  It is a great explanation of this test approach, originally devised by Creighton Audette in the 1950's.  It will frame the method using long range distances and rifles.  The concept and approach is important for our purposes as I apply the Ladder Test to a iron sighted Blackhawk, indoors, at 25 yards.

Let's Get Started

Now the you have the concept behind the a ladder test, there are a couple of tools that make it much easier to handload one cartridge each of several different charges.  Using a powder measure is possible but time-consuming and a just not-much-fun.

Borrow or purchase a powder trickler.  They are easy and quick to use.  The Lyman below is what I use, but all the major brands have good ones available (this cost $20 at Bass Pro Shops):

Use the trickler to feed the powder directly onto your scale.  You can feed it quickly, or as slow as 1 speck of powder at a time.  Great for weighing lot's of different loads.

Next is a funnel, to get that weighed charge into a sized, primed and flared 357 magnum case.

That's all it takes, assuming you have the scale and other reloading gear already.

The Ladder that I worked up and loaded for this test is:

  1. TL358-158-SWC that is lapped and drops 168 grain bullets
  2. H110, this is really an attempt to work up a great load with combination because I don't have one for this bullet
  3. Charges in the ladder:
    1. 11.6 grains of H110
    2. 11.9
    3. 12.2
    4. 12.5
    5. 12.8
    6. 13.1
    7. 13.4
    8. 13.7
    9. 14.0

I used a few extra rounds to warm and foul the barrel.  This target is the result; 25 yards from a rest and iron sights:

Revolvers (handguns in general) don't always walk up the ladder.  Sometimes a heavier charge will shoot lower.  In this case, that happened.  Recalling the article on how to do this testing, look for 2 or more holes close together, with sequential numbers only.  There's one set that shows the sweet spot, numbers 7 and 8.  That puts a nice sweet spot at 13.5-6 grains, that should provide good groups.

I have an advantage at this point in working up the load.  From prior test results (thousands of rounds) I know the diameter, OAL and that this bullet design has the capability to shoot sub-1-inch groups at 25 yards.  That should decrease the time spent refining the load for maximum accuracy.

In Part 2, A range report using the load the Ladder Test produced.  Also:  How does the Blackhawk do?  Ladder Test results using 700X and Unique will follow.

Have fun shooting, and keep the groups small.

No comments:

Post a Comment