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.

Derrick's Crosman 180 Repair Part 3

One thing that bothers me while shooting many of the vintage Crosman rifles is the protruding nut that holds the action to the stock. It seems like it's right where I want to rest my support hand.

I cut a piece of 7/16" drill rod to make a new locating stud.

Chucked it into the Taig 3-jaw and faced off. Turned down about a half inch of the end to 0.188" diameter.

Done.

Need a shoulder att the base of the 0.188" section to recess into the wall of the gas tube and anchor the valve. The shoulder was cut to 0.2675" diameter and is 0.062" long.

Threaded the 0.188" portion #10-32 with a thread cutting die.

Cut a relief groove at the base of the thread to allow the thread to bottom against the valve.

Threaded into the valve.

Since I've moved the valve forward by 0.088" in the gas tube, I must also make a new exhaust port in the valve and seal off the old.

A transfer punch provides the mark for the new port location.

Gutted the valve and ready for drilling. You know what's next... Spotted and drilled.

I matched the original hole diameter with a #21 drill bit. I didn't look up the actual diameter. The bit simply fit nicely into the old exhaust port. A drill bit chart says the #21 is 0.1517".

Need to seal off the original exhaust port hole. Just tapped the old hole to #10-32. Catch what Crosman did? They uses the tapping drill for both the exhaust post hole and the #10-32 stud thread. One bit for 2 jobs on the valve.

A short #10-32 setscrew and some permanent thread locking compound should seal the old exhaust port hole.

Installed the setscrew flush with the bottom of the hole inside the valve. This should keep the volume inside the valve the same as before. Again, reassembled and pressure tested the valve. The exhaust port lined up correctly in the gas tube and the valve went "bang".

Back to that new locating stud.

The 180 stock had a 7/16" diameter hole already in place.

Intentionally left the stud long to allow for sizing. Ideally, I want the end about half an inch from the bottom edge of the stock.

Cut the stud off and faced what will be the bottom end.

Nick shows edge finders, I show center drill bits. We cover all the bases that way.

Drilled an inch deep with a #7 bit.

Tapped 1/4" x 20 using a Jacob's chuck held in the lathe's tailstock.

Several months ago, I made a similar recessed nut for a Crosman 147 BP that was never blogged. It worked so well I won't mess with success. What is this? This is the upper pivot bolt from a Shimano rear derailleur. This one is stainless steel and has a very thin, wide head with a 5mm allen key broaching. Gotta have one? Go make friends at the local bike shop. (take good beer!) They'll likely give you a couple scavenged from broken derailleurs from the scrap parts bin. Tell them I sent you. (--only if you take the beer)

The head recesses into the Crosman stock(s) perfectly. The bolt is also made from top quality steel--which, of course, works against the ease of machining.

Grabbed the threaded end in the 4-jaw and trued. Turned the body of the bolt down to 0.250".

Parted off at the threaded end. Not shown: Cut 1/4" X 20 male threads on the Shimano bolt.

Looks promising.

The new locating stud.

Threaded into the valve.

Valve body tightened. Gun was reassembled--see Part #1 and do in reverse.

Insert action into stock.

Remember the bolt uses a 5mm allen wrench.

Hey! a smooth spot to rest the hand. I tend to shoot these guns from a 10-meter type position. When I set the forend on top of my fist, the old nut was in exactly the wrong place. The gun can still be converted back to original in a few minutes if so desired.


Snugged up. I'll paint the head black to match.

And a few more details to handle: The trigger could stand a tune up/adjustment, and uh, well, there's no rear sight on the gun--just a couple threaded holes. When James dropped off the gun, it had a broken Weaver scope attached with an odd mount clamped to the receiver. I'm not into point or instinct shooting, so I'll have to do something about that. Maybe I should mount a tactical quad rail and a bayonet and call it good? I'll probably just install a nice vintage open sight that Nick sent me in a care package a while back. Wait, what about a laser?

Still more to come in a few more days.