New Front Sight For The BSF S20

Still haven't started the rear sight project for the 22XX.  It's one of those projects that I have to be in the mood to tackle.  While I was thinking about it and the dovetail cutting it probably entails, I remembered that my BSF S20 WCM pistol needed a new front sight.
















It's the weirdest looking thing.

I'd previously mentioned that the front sight wasn't appropriate for pistol shooting.  Really? "Barleycorn" sights on a pistol?  What were they thinking?

Removed the hood.

It's dovetailed in place.

Brass drift and a hammer blow knocked it out left to right.  Was hoping the dovetail was 60 degrees as I have a few dovetail cutters in that size... but it's not.  Didn't bother to figure out what it actually is--though it's probably 45 degrees.

Looks like it was made from a piece of round stock.  The widest dimension is approx.  0.500".

Cut a piece of "free machining" 12L14 steel. 

Faced the ends down on the lathe. 

This is a 3-sided 2nd cut file with a "safe" side--I sanded the teeth off one side on a belt sander.

Started to freehand cut a dovetail. Then I realized that I'd over cut the depth and had to start over.  Freehand cutting dovetails is insane asinine tedious.

Flipped the piece in the vise and cut the other side.  Just did it by eye checking against the cut in the barrel.

When it looked like it was close, I faced down the bottom of the dovetail in the lathe until it was almost bang on the money to the bottom of the slot width.

A couple file stokes here...

and there...

As well as some test fitting.

I quit with the filing when the angles matched and it would slide in about 3/4 of the way home.

Forgot to mention--the dovetail I filed had to be very slightly tapered so it wedges tightly into place as it's driven into the slot. The black mark is just a reference so I could shoot the pistol and verify its correct height to the rear sight.

Wanted the rear sight somewhere in the bottom third of it's adjustment range at approximately ten meters.

Faced the sight down until the height was correct and the pistol was grouping to point of aim along the horizontal plane.

Here's where it got tricky.  The dovetails are roughly parallel to reach other--not exactly parallel, but close.  I guestimated by splitting the difference in the taper and installed the piece in a 0.500" 5C collet.  (Actually, I just eyeballed it and thought it looked OK.)  The collet went into a holder called a collet block.  This is a square collet block and it allows one to rotate the piece in 90 degree increments. There are also collet blocks that are six-sided to allow for 60 degree work rotation.

Changed the set up and got rid of the parallels in the vise.  Located the block even with the end of the fixed vise jaw.  Set the travel on the mill and cut the flat that will become the sight blade.

Turned the block over and cut to the same depth.  Measured the thickness, did some math and set the depth gauge on the mill to produce a 4mm wide sight blade--my preferred width for shooting 10 meter pistol targets.

Turned the block upright and used a 60 degree dovetail cutter to undercut the rear of the sight.

Some clean up with a wire brush and here it is next to the original sight.  It's taller, as the rear sight used to be buried at the bottom of it's elevation adjustment.

Blued. 

A few milling marks on the side that aren't worth polishing out.  The close-up with the flash always makes the tool marks look worse than they really are.  Ya can't see them while sighting.

Tapped home.  Took a couple good whacks with a maple block to center the sight.  It'll never move again on it's own.  It's gotta be tight to stay put under recoil.

Those nice sharp edges that make sighting so much easier really chew up the hand when cocking the pistol.

Oddly enough, the hood fit exactly on the new blade.  Guess the old sight was made from a piece of 0.500 round stock after all.

It's perfect.  After a bit of shooting, I filed open the rear sight notch open to 3.8mm and the sight picture is ideal.

We'll have more soon.

Another BSF S20 WCM Tear Down Part 2 Final

Finishing up the S20 today.

Glossing over most of the steps since this is the second time around for this model on the blog. I cleaned all the sticky crud out of the compression tube and all the various components. Polished the back end of the piston body, cocking rod notch, sear...

Once it was clean, I soaked the leather piston seal in oil then gave the internal parts a thin coat of Buzzy's Slick Honey.

Piston rod is brass brazed into the body.

The brass was covered with verdigris when first removed.

With the piston in the tube, trying to reinstall the barrel/breech block to the compression tube took some patience. The forks on the tube are extremely tight to the breech. The cocking lever also needs to be reinstalled through the trigger block and into the slot.

Used a dental pick to lift the trigger spring out of the way while seating the cocking lever. Once the spring was out of the way, the lever was positioned then the breech was installed into the forks. A transfer punch was used as a slave pin for the barrel pivot.

Was having trouble getting the peined rivet aligned with the far side of the trigger block. It kept moving off center as it was binding on the cocking lever. With a chainsaw file, I added a small radius into the cocking lever for pin clearance. Exact location not critical as the barrel can be broken open to align the groove with the pin. The red vinyl tape on the slave pin prevents it from falling out.

Click any image to enlarge for more detail. I shielded the gun with foil to prevent getting metal filings into the action. Sorry, I didn't show that in the pics.

Barrel opened to align the groove with the pin.

Pin tapped home and barrel pivot pin installed. Yes, glossing.

The rest of the reassembly was uneventful. Spring installed...

Added a thin rotation washer to the base of the spring guide.

Remember that there are two cross pins for the sleeve/spacer/endcap whatever you want to call it. Pinned the rearmost hole first (without the rear sight assembly) to restrain the mainspring. This allowed for much easier installation of the sear on the forward pin as I was no longer fighting the mainspring while attempting to align the cross holes in the tube, sleeve and sear--then pin it all together.

Removed the rear pin after seating the sear and sear spring. The forward pin is now retaining the mainspring. Installed the rear sight block and it was pretty much a done deal. Finished the gun by installing the grip.

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.