Fixing a Benjamin 312, Part 3

The counterbores cut, I had to make a new pivot pin.

I turned an extra long shoulder that's 5/16" diameter, with a 3/16" shank, and parted off to length, leaving a short 5/16" diameter stub.

Which I then drilled.

And reamed to 3/16"

I then parted it off and deburred the cut off side.

The new pin assembly.

I used a jewelers saw to slit halfway through the bushing.

Then halfway the other way.

This leaves a section that can be compressed by the pin locking screw, which will retain the entire pivot pin assembly.

The head side of the pin in the counterbored hole.

The bushing side.

The rifle pumps up fine now and I feel a bit more secure that the pump force is bearing on the tube rather than the tiny plug screws. The rifle seems a bit underpowered, as I'm only getting about 10 ft/lbs (580 fps w/14.3 gr. pellets) with 8 pumps, although another four pumps gives the same level of power. If I get bored in the future I'll tear the valve down and see if the seals need replacing, etc.
Another old ugly beater restored to functioning condition!

Fixing a Benjamin 312, Part 2

I figured out a strategy for dealing with the wallowed out hole in the pump tube.

Turning a 3/16" diameter pilot with a 3/32" shank for a interchangeable piloted counterbore.

The finished (I still had to turn the pip off the end) pilot.

Mounted in the counterbore. The counterbore is 5/16" diameter.

Counterboring the tube and plug with a hand drill.

On the left side I counterbored about 3/16" deep.

On the right side I went 1/4" deep so that the screw which normally holds the pivot pin would enter the counterbored section completely. The brass cut freely. Now to make a new pivot pin.

Fixing a Benjamin 312, Part 1

I bought a Benjamin 312 rifle off the Yellow classifieds the other day, listed as "missing pivot pin". The price was right so I bought it. I figured it would be pretty easy to fix and I was already comfortable with the design having fixed my 317.

I stripped the end plug. The pin screw was worn at the end, should have a point.

The piston was very greasy, but that cleaned up fine.

I made a new pin from a dowel pin.

The pin in the plug.

I ground a flat, rather than a vee groove as on the 317, because of the missing tip of the plug screw.

The rifle. Worn and used, but I think it's beautiful in it's own way...

As with all of life, you never think to check things that should be obvious (and I'm sure it didn't occur to the seller either). The hole for the pivot pin is wallowed out on both sides of the tube. I'm not entirely sure how that would even be possible unless the rifle was pumped without the plug in place, but there it is. This means that the pumping force is bearing on the two skinny little screws that retain the plug in place.

I don't want to solder in a patch as the entire barrel is soldered to the tube, and heat would discolour things as well. Plastic steels are unlikely to work and besides I want to be able to tear the rifle down again for maintenance. So I will do a little thinking and come up with a solution, as always.