Monday, June 7, 2010

The 1377 Project, MKIII Piston

Now to make the MkIII version of the pump cup modification.

.25" brass tubing this time.

Coring the hole.

I cut the cup end off with a knife.

Much better than trimming by hand.

Turning a shank and the taper.

Checking for depth.

Shoulder, threads, check!

Looks like it works.


Cleaning up the face.

Slotting the head for a screwdriver, .032" wide and deep.

The piston head, all done.

It stopped raining long enough to run a few shots over the chronograph. With 10 pumps, CPL 7.9 gr. pellets, I got a very consistent 757 fps (+/- 3fps). That's a 17 fps improvement over the o-ring! I would have been happy had it been a bit slower. I'll be trying this mod in all the Crosman pumpers from here on out.

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