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Constructing an Aluminum 13xx Pump Rod

The plastic pump rod that comes stock with our 13xx is adequate for the factory gun, but falls short of the demands placed on it by a modified gun. The plastic has a tendency to compress under pressure, decreasing the effectiveness of multiple pumps. In this article, we'll use aluminum alloy rod to construct a solid pump rod capable of handling the most brutal of punishment a modded gun will throw its way.

Tools and Materials Needed
Here is a list of essential tools for this task:

Dremel with cutoff wheels and carbide cutter
Drill press & vise with good selection of bits
Bench grinder w/ med & fine wheels or Sander
Pliers or vicegrips

Here are the materials you will need:

5/8" Aluminum rod
Old pump rod
Pump cup
13xx or similar tube

Begin by placing the old plastic pump rod next to your 5/8" aluminum rod. See Fig. 1 Proceed to cut out your new pump rod. See Fig. 2 If you have ground the face of your valve flat, you'll want to cut your new rod slightly longer than the old one to maximize compression, as Fig. 3 illustrates.

Mark the spot where the pivot hole is to be drilled. See Fig. 4 Now it is time to take measurements. You'll need a 9/34", 3/16", 15/32" drill bit for this step. Begin by measuring the pivot hole in the plastic pump rod. See Fig. 5 I measured mine to be 3/16" wide. While you are taking measurments, measure the slot See Fig. 6 and the hole for the pump cup. I measured the slot to be 9/34" and the hole for the pump cup at 15/32".

Drill out the pivot hole, making sure that you drill in the dead center of the rod.See Fig. 7 Once the pivot hole has been drilled, drill a 9/34" hole perpendicular to it. Using a cutoff wheel on your dremel, cut a slot that opens this hole to the rear of the rod. I used a tungsten carbide cutter as well to smooth out the cut. Check often for proper fit. If the cut isnt perpendicular to the pivot hole, you'll have to correct your cut, as the pivot pin will not fit. See Fig. 8

Once the pump rod fits the pump arm and pivot pin, See Fig. 9 it is time to reduce the diameter of the pump rod. You'll need to fire up your bench grinder at this stage. Applying mild pressure against a medium wheel, rotate the pump rod in the opposite direction of the wheel's spin. Check often for proper fit. See Fig. 10 Keep the rod rotating to avoid flat spots.See Fig. 11

*IMPORTANT* Since posting this article, I've been notified that aluminum and bench grinders are not a good combination. Instead of using a bench grinder, using a sander to shape the metal is a safer practice. If you do use a bench grinder, be sure to keep the wheel clean and clean up all aluminum dust.

When the rod slides freely through the tube, See Fig. 12, you are ready to drill the hole to accept the pump cup.

You'll need a 15/32" drill bit chucked in your drill press to do this step. Carefully clamp your pump rod in a vice, making sure that the rod is square. Align the pump rod so you will drill it dead center. Go ahead and drill a hole through the top about 1/3" deep. See Fig. 13 Press the pump cup into this hole, it should fit very snugly. It might take a little bit of pounding to get it in, but once it is in, it shouldnt come out. You are now ready to reassemble your gun for testing. See Fig. 14