Another BSF S20 WCM Tear Down Part 1

Apologies, as Nick has already covered a BSF S20 overhaul in fine detail several months ago. Mine feels as though the mainspring is covered in cold molasses and obviously needs some attention, too. I'll be brief, as I don't have much to add--at least in part one. I believe I did a bit less disassembly than he did and it certainly went easier.

A pic of the BSF S20 by itself doesn't give scale for it's true size. A Crosman 2240 provides some perspective.

The WCM model has thumb rests on the stock. It's not really just a grip when it uses this much lumber.

Started the same as Nick did before taking a couple small departures.

First removed the rearmost pin and set the rear sight assembly aside.

The second pin holds the sear and end tube. The drift is now retaining the mainspring.

Another view.

Sear, spring and small spring guide.

Compressed the end tube slightly against the bench and pulled out the drift. Slowly released the mainspring and guide.

The grease on the mainspring has hardened and has the consistency of roofing tar.

Piston is full of the tar, too. Can't get the piston out without removing the cocking lever first.

The breech pivot is a pin rather than a shoulder bolt.



Knocked the pivot pin out and found that it also retained the plunger and spring. Actually, the plunger fired across the bench. Clever design. Most guns use a separate pin to hold the plunger/spring in the breech block.

Nick's posts made several mentions of the aggravation he had while dealing with the peined pins on the trigger block. There's three of them, but only the front pin holding the cocking lever against the compression tube has to be removed to extract the piston. Took care to not damage the leg of the trigger spring. Didn't knock the pin all the way out.

With the pin removed, the lever was wiggled from the cocking slot then the piston body was pulled free.

The leather seal is in dandy shape despite being covered in sticky glue.

More soon.