Derrick's on a Beeman P17 Overhaul, Part 1

Buddy Jason recently sent me his Beeman P17 for the spa treatment. Since I've had quite a few email queries about the P17, I thought a tear down and rebuild illustration guide might be worthwhile. T.W. Chambers & Co. has a great schematic of the Beeman P3 that we can use as a reference point here. Keep in mind that the P17 is a Chinese sanctioned copy of the German Beeman/Weihrauch P3.

Unlatch the pseudo hammer and open the gun as though cocking. With the gun open, use a 2mm allen wrench and loosen the set screw as shown. It's unnecessary to remove the setscrew, just back it out a turn or two so it's no longer bearing against the cross pin. Drift out the cross pin.

Pull the entire piston right out of the compression tube.

This step is completely unnecessary for a routine tear down. I'm going to crown the barrel on this gun as I get further along. I removed one of the small e-clips on the barrel pivot pin and using a drift, pushed the pin out.

Another view. You can see the small e-clip just above and left of the cotton swab.

Using a 2.5mm allen wrench, remove the right side grip panel. Find the seam on the bottom with a fingernail and gently separate. Some of the internal pivot pins may stay attached to inside of the right grip. That's OK. Note their location and pull them out of the grip. Try to not scar them up with pliers.

Using a small pair of needle-nosed pliers, pop the tails of the 2 springs out of the left grip panel to relax the spring tensions.

Pull the pivot pin out until it just clears the mounting hole and remove the sear straight back and out.

Another view. Holding the sear. Pull it straight out.

Unhook the torsion spring from the part that looks like the number 7. Weihrauch refers to this part as the true "hammer".

Remove the hammer's torsion spring.

Unhook the lower end of the coil spring attached to the pivoting lever on the hammer assembly.

Another view.

Next, unhook the top of the coil spring from the pivoting lever . Set the spring aside. Pull the hammer's axis pin out slightly and rotate the hammer assembly as shown on the valve stem and it will lift right out.

Here's the #7 looking hammer assembly. The pivoting piece at the top is the lever. Coil spring shown detached but oriented correctly. Upper loop of the spring fits into the round hole in the lever.

Removing the hammer axis pin shows there's yet ANOTHER spring inside the hammer. Note the orientation of the loop.

I pulled the trigger axis pin and the trigger came right out.
More to come.

Resealing the Sheridan Model C

This was a comedy of errors. Basically the Sheridan goes back together in reverse of disassembly, below are notes and comedy that point out a few details.

I used the shim punch to cut concentric seals from lead and rubber.

The inlet valve seal is wrong. I know that now. I cut it way too large in diameter.

You would think I would have caught on...

The exhaust valve spring is tapered, small end towards the rear.

The exhaust valve seal looked clean so I decided to reuse it.

The large rubber washer is also twice as thick as it should be...I thought I had removed the old one but couldn't find it...

At least I got the lead seal right.

The nut is conical to seal against the lead seal.

The face you see when you look down the tube.

Ready to reassemble. I found I had to trim the length of the square section on the wrench to the length of the nut.

That bolt spring...

I placed a feeler gage against it to compress and slid the bolt back in.

Then screwed the locking lug back in. I think it's best if the flats are vertically oriented on the sides so that it smoothly contacts the cam.

The plug goes back in oriented as shown. Then I couldn't screw the valve in...I discovered that the old rubber seal was still in the gun and half as thick as the replacement...preventing me from screwing in the nut (because i now had 3x the thickness)...so I reused the old one and got it all back together.

Well after getting it back together (in reverse of disassembly) it wouldn't work...still not holding air. So I replaced the inlet valve spring with the one on the left. You can see the old rubber seal above the springs

Still no good...so I turned up a new inlet valve seal from teflon. Look familiar? It worked so well in the Benjamin 317 that I figured why not?

You can see how I didn't make good contact with my replacement rubber seal. Well I'll figure it out next one I reseal...note that I put a stem on the teflon seal on the spring/valve end just as I did on the Benjamin 317. I don't know why I did it instead of just making a disc but it may be stronger this way and resist deforming in the center. I do lose a bit of valve volume this way.

Well the gun shoots about 645-650 fps at 8 pumps with Benji .20 cal cylindrical pellets. So it works! It also held air for several days, which is a good test.

Disassembling a Sheridan Model C, Part 2

And on I go...

Cleaned off the worst of the debris with a toothbrush.

This is wrong. I punched out the pin that holds the trigger housing.

Then when I went to punch out the trigger pin the housing just rotated around...

So I held it with a slave pin. Better to first punch out the trigger pin, then the housing pin...

The housing comes out with the hammer spring and guide. Note the trigger spring and trigger spring guide on the right.

The hammer spring and guide looked good.

I loosened one screw on the safety (flat) spring.

Then the other and removed the safety.

The hammer slid out.

Looks just like the Benjamin 317 I resealed.

So I used my handy tool.

And then the valve puller.

The valve connected to the puller.

The valve was dirty but looked ok.

The inlet valve spring was a bit overcompressed, or maybe they're all like that.

The inlet valve seal was definitely bad.

One messed up seal.
Resealing comes up next...

Disassembling a Sheridan Model C, Part 1

Yet another airgun to disassemble and reseal (it wouldn't hold more than one pump...bad inlet valve), this time a Sheridan Model C.

A classic rifle.

Removing the stock.

The rifle without the stock.

Punching out one roll pin.

Then the other.

Frees the pump lever.

The end plug is removed.

I slid the pump up to expose the pin that holds the linkage and pushed it out.

The pump cup looked good.

The bolt cam cover plate gets removed.

As does the cam plate that the bolt screw locks against. This is adjustable BTW.

Using my fancy Sheridan tool to remove the bolt cocking lug.

I kept my hand over the bolt as I withdrew it so that spring would not fly across the room.

Just a bit dirty around the trigger...more to come...