Tuesday, May 12, 2009

Derrick's Crosman 180 Repair Part 4

The single-stage trigger in the 180 was way out of anything that I could call "normal" adjustment. Of course, I hadn't bothered to even think about the trigger adjustment until the rifle was functional, so here we are.

Removed the screws holding the trigger to the gas tube. One at each end.

Removed the two side-plate screws and exposed the trigger blade and sear.

Lifted out the trigger blade...

and polished the sear contact surface (at the top front) on the buffing wheel.

Greased the pivot pins and the sear/trigger blade interface.

There are 3 adjustment screws on the rear of the trigger housing. The set screw on top adjusts the amount of sear contact. Less contact equates to a very short trigger pull. Adjust this first. Err on the side of safety . When in doubt, add a bit more contact by backing it outward. You can manually set the sear, then pull the trigger to test for proper function.

The lowest adjustment screw bears directly on the trigger return spring. It should be adjusted after the sear contact is set. A lighter weight spring doesn't really improve things much, as the spring can be set up with very minimal tension with the screw.

Finally, the center screw functions as a trigger stop. It must be adjusted last to block the trigger's rearward travel after tripping the sear. Over adjusting it too far inward will not allow the trigger to release the sear. Err on the side of function by backing it out just a bit more than required to fire.

Side plate reinstalled. The central hole in the side-plates allow a visual check on the amount of trigger/sear contact. That's good design. Functionally, it's one of the best single-stage triggers ever put on a gun of any kind. It can be finely adjusted and it's very repeatable from shot to shot. It's one of the reasons that vintage Crosmans are still so highly regarded by shooters today. This trigger destroys almost every other trigger being produced today in modern sporting airguns.

Note: This trigger is what's referred to by collectors as a "Second Variant". It's the one you want your gun to have. Crosman used this trigger on many, many rifles--both CO2 and multi-pump pneumatic. It was used on the 160/167, 180/187 and probably a few that I don't know about. I'm not any kind of authority on vintage Crosmans, but I believe this trigger started showing up in the early 1960's--I think somewhere around '62 if I recall correctly. Check the Crosman EVP's if questions arise.

A white paint marker across the engraving.

Dried and wiped off the surface leaving the lettering filled in.

The rear sightless gun. The holes are factory tapped #6-40. The original rear sight was a simple piece of bent sheet metal. Nick bought a rear sight assortment several months ago and sent a couple along in a care package. He's previously blogged the installation of one such sight here.

One sight he sent was a fully adjustable steel Knight's that matched the 180's finish.

One small problem. The 180's rear sight holes are 0.525" apart c-to-c and the Knight's are 0.575".

Using the milling attachment on the Taig lathe, I ovalized the central mounting hole with a 1/8" end mill.

I figured this was just as good as drilling a new hole.

Need to mill a counterbore for the slot to recess the head of the #6-40 mounting bolt. A 3/16" end mill worked perfectly.

Slightly blurry, but you get the idea.

Like Nick, I chose to re-profile the rear sight leaf. The original had a crescent shape and a small, shallow notch. I cut some tiny brass strips to act as packing blocks for the milling vise and milled the top of the sight flat.

Then using a 1/8" end mill I recut the notch both wider and deeper.

Another view. I made a single pass after aligning to the center of the old notch.

The mounting screw heads were a bit too large for the counterbore so they were turned down slightly to fit.

Sight installed. I could re-cut the notch a bit deeper as I'm just at the lower end of the elevation adjustment at 10 meters, but it's on target and far better than the old Crosman sheet metal
sights of the '60's.

More views. The white filled lettering also looks nice--at least to my eye. The radii don't quite match from sight base to receiver. From a few feet away it's hardly noticeable. Not enough metal in the sight base to profile. Not worth it (to me) to make a shim--at least not until the stock gets refinished.

I'm torn between leaving well enough alone and refinishing the stock on both this rifle and a recently repaired Crosman 147 BP. On the one hand, the stocks are in good cosmetic condition for what they are. On the other hand, varnish is really not a good look for a gun stock.

So....more 180 stuff to come. Just not in a couple days.

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