These General Measurement Instructions Below
are for Ruger Double Action Revolvers - GP100, SP101, RedHawk, Super Red Hawk and Alaskan, Security Six, Speed Six, and
Police Service Six but generally apply to Most Firearms.
The easiest way to Measure your Trigger or Hammer
assembly is with a simple blade type feeler gage. Trigger assembly and Hammer assembly Measurements are generally done
in the same way. In the Video Example below I show the basic way to measure the Hammer Clearance to fit and install
Hammer Shims. Fitting and installing Trigger Shims would follow this same basic example.
These General Measurement Instructions are
for Ruger Double Action Revolvers, but generally apply to Most Firearms.
Trigger Shimming; Use the Feeler
Gauge to Measure the Total Side Play between One Side of the Trigger and the Frame. In this example there will be about
.009” trigger side play, yours may vary. Subtract .002” to .004" for Ending Clearance and divide the
remainder by 2. In the example of an .009” gap, .009" - .003" (.002" to .004") =.006”;
.006"/2=.003” Take two shim washers .003” thick and install them on both sides of the trigger. This will serve as a bearing surface and will keep the trigger from moving sideways when pulled. It will reduce friction
and force the Trigger to make a more uniform contact with the Hammer. In the case of Trigger/Frame clearance of less
than .006" a single .002" or .003" shim installed on the Left Side of the Trigger will give benefit to a
Right Handed Shooter. After installing the shims, make sure the trigger moves freely with No Binding.
With the Hammer Main Spring Removed to Relieve Tension, Measure the Total Gap between One
Side of the Hammer and the Frame. Unlike the Trigger, you will generally see a little more Clearance at the Hammer. This Clearance allows the Hammer to Rub the Frame, Causing Drag. Look at the Sides of the Hammer, if you see Arc-Like
Scratches, it means the Hammer has been Dragging on the Frame. This Reduces Hammer Thrust and Speed, and in Extreme
Instances could cause Light Strikes. Installing a Shim at the Hammer’s Pivot Point Reduces Side Play, and
adds a Bearing to Reduce Friction and Prevents the Hammer from Rubbing on the Frame.
Use the same formula
for the Hammer as the Trigger.
Use the Feeler Gauge to measure the Total Side Play between one side of the Trigger and the Frame. In this example there will be about .012" Hammer Side Play, yours may vary. Subtract .002” to .004"
for Ending Clearance and divide the remainder by 2. In the example of an .014” gap, .014" - .004" (.002"
to .004") =.010”; .010"/2=.005” Take two shim washers .005” thick and install them on both
sides of the Hammer. The best way to do this is to install the Hammer then slide the Shim down the side of
the Hammer. Use a Feeler Gauge Blade to push the shim into position.
After the Hammer Pivot Pin is seated, Check the Hammer for Free Movement, and be sure there is No Binding.
Ruger Double Action Hammer Dog Shims; Shimming a Loose Hammer Dog can help with Double Action Trigger Pull. Use a Feeler Gauge to Measure Total Clearance,
and allow a minimum .002" after Installing Shims Shims are available in .002" through .009"
Barrel-Cylinder Gap and Endshake; The gap between the back of the barrel and the front of the cylinder is known as the Barrel-Cylinder (B-C) gap. The Front-To-Back
Movement of the Cylinder is the Endshake. In order to properly measure these clearances you will need a Feeler Gauge
Set. K-D Tools USA Made # 161 Deluxe Feeler Gauge is available all over the internet and at most good auto parts stores for
under $10 To check B-C gap, hold the cylinder rearward and insert the (thickest that will fit) feeler between the Barrel
and the Cylinder, this is your Barrel-Cylinder Gap, write it down, it should be between .004" and .008" Next,
hold the cylinder forward and re-check the gap, write it down. There may be no clearance here at all, the cylinder may
touch. The difference between the two numbers is the amount of movement or Endshake your cylinder has, it should be
between .001" and .004" on most Ruger Double Action Revolvers, other manufacturers clearances may vary Our
Cylinder Shims can be used to adjust your B-C Gap and Endshake. Available in the following thicknesses; .002",
.003", .004", .005", .006", .007", 008" and .009"
Kevin Wilson's Trigger Job Guide Applies to all Ruger Double Actions
Bolt Shim Installation; Installing bolt shims requires fitting by hand, not measurement. Start
with the thinnest shim, (.002") and install, then check to see how your bolt closes. As long as it continues
to close normally, continue to add shims .001" at a time, stacking as necessary. When you have installed
enough shims that is begins to be hard to close, remove .001" so it closes normally or just (ever-so) slightly
tighter than normal. If you have to force or put undue stress on your bolt, you should reduce the number of shims.
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