A .22-cal, 8-inch barrel Model 112
The Crosman series of bulk fill CO2 pistols and rifles were produced from 1950 to 1955. They are a rugged, straightforward design that will give many years of service when properly maintained. Unfortunately many of these guns have spent years without use or lubrication and no longer will hold pressure. In this case you can either send your gun off to be repaired or do the job yourself. There are a number of people who will do the job for a reasonable price. I have used Rick at Precision Pellet and can recommend him for parts and service; I have not used any one else but a question posted on the Yellow forum will get you a number of names.
If you choose to do the job yourself you will need a seal kit; these can be purchased from Precision Pellet, AB Airguns, and others. You will also need to make two custom tools for proper disassembly. If you have done airgun or firearm repairs this job should not be too difficult. One thing to remember is that a number of the parts are brass and can be damaged if too much force is used. Patience is a great help.
Various screwdrivers, all straight-slot. A gunsmithing set is best but regular screwdrivers will work with care.
One or more picks to remove hardened seals
Wrenches as needed for holding parts
Tweezers may be required during reassembly
As mentioned above you will need to make two tools:
To remove the fill cap you will need a short section of conduit or iron pipe modified to hold a drift punch or a drill bit. If you examine the fill cap you will see a pressure bleed hole in the circumference of the cap. Select a punch that fits this hole snugly. For one of my guns the solid end of a drill bit worked best; for another a punch did the trick. The conduit or pipe will need to be able to fit over the fill cap. You will need to drill a hole near the end of the conduit or pipe so the punch can be placed through the conduit into the pressure bleed hole. By supporting the punch to keep it perpendicular to the fill cap you should be able to remove the cap without using a wrench.
By using a punch through the side of a pipe section or conduit the
fill cap can be removed.
The valve body is held in place with a grooved lock nut. You can use a piece of conduit and mill one end to have two pegs to fit the groove. Drill two holes through the conduit at the opposite end so you can use a Phillips screwdriver, punch, or other rod for leverage. I purchased a cheap 1/4 inch socket set and used a Dremel tool to produce the pegs; a 1/4 inch drive and an extension make the job easy.
Not pretty but it will work. The lock nut does not require too much force.
A new seal kit will be needed; it is the same set of parts for all of the bulk fill Crosmans (both pistols and rifles.)
From left to right: exhaust valve body o-ring; exhaust valve seal;
check valve spring; fill cap o-ring; fill check valve seal; filling head seal.
Cleaner/degreaser such as rubbing alcohol
Moly grease or other lube (optional)
If you decide to do the job, expect to take two to three hours for the first time. If you are not confident you can finish the job, DON'T START! Gunsmiths, like mechanics, do not like getting a box of parts to put back together.
1. Very Important: make sure the gun is unloaded and has no pressure. It can be dry-fired untill all pressure is exhaused (assuming it was holding pressure for at least a little while.)
2. Remove the two grip screws.
3. Remove the grips. This can be difficult as the plastic grips tend to shrink over time and become tight. To get them started you can use a medium flat blade screwdriver and gently pry down on the top of the back of the grip. You should be able to move the grip enough that you can pull down and back while wiggling it. If you happen to damage the grips the current 1377/1322 grips fit perfectly and are inexpensive.
If the grips won't move, pry down with the flat of a screwdriver.
4. Remove the two screws holding the grip frame to the gas tube. It is best to hold the frame to the tube while removing the screws, turn the assembly upright, and then separate the grip frame from the tube. The pistol has the same tiny safety spring as a 1377 that is just as eager to get lost.
With the grips removed the grip frame screws will be accessible.
Like the 1377 the old pistols have a safety spring that is easily lost.
5. Back the power adjuster most of the way out. Remove the two small screws from each side of the rear end of the gas tube. These are the last bolts holding the back end cap on. To protect the threads of the small screws I hold the end cap against the tube until both screws are removed. I ususally put the screws into the end cap so they cannot wander off.
Remove the two side bolts and the hammer end cap will come off.
6. The hammer spring and hammer should now slide out.
7. Turn the gas tube upside down; push the bolt back in all the way. If you look through the slot in the bottom of the tube you should see a pin in the bottom of the bolt that pulls the hammer back. If it is not there is already has fallen out and you will need to find it.
8. Remove the bolt. Do this slowly as there may still be a pair of ball bearings with a spring between in the middle section of the bolt. These are not required for proper operation of the gun; I am not sure of their exact purpose.
More small parts to lose: two ball bearings and a spring reside
in the through hole in the bolt body.
9. Turn the gas tube upside down. Just aft of the front grip frame screw hole you will see a hole in the tube with a silvery depression. This is an alignment hole in the valve body. The hole is in line with the transfer tube into the receiver and must be visible when the valve body is replaced.
10. Look into the open end of the gas tube; you will see the lock nut. Remove it with tool #2. It is conventionally threaded - turn to the left to remove it. Pay attention to the general amount of force to remove the lock nut; it will not require a great amount of torque during tightening.
11. Using tool #1 and a punch or other rod, remove the fill cap. It should be possible to do this without using any other tools for leverage. Set the fill cap aside for the time being; it contains two seals that will be replaced.
Electrical tape is used to protect the finish of the fill cap. To remove the end cap pass
the punch through the hole drilled in the pipe section and into the bleed hole.
12. Look down the gas tube from the front. You will see a hole and the back of the check valve. Using a long punch or other round tool press the check valve down; it will travel about three eights of an inch. Continue to press down to drive out the valve body. It may take a couple of soft taps from a hammer to get the valve body to move. Do not use too much force here. Note the order of how the parts come out.
From left to right: lock nut; exhaust valve body (missing the o-ring) with the gas
port on top; exhaust valve assembly; check valve spring; check valve. The long
end of the check valve goes in first during reassembly.
13. Inspect and clean the gas tube. Make sure that the threads for the fill cap are clean.
14. Inspect the exhaust valve body and the exhaust valve. On this particular gun there was some minor surface discoloration due to a lack of lubrication. Remove any dirt or corrosion.
15. Replace the o-ring on the exhaust valve body. I like to get a little pellgun oil on my fingers as I do this; it helps the valve body slide back into place a little easier.
16. It is not obvious from a visual inspection but the stem in the exhaust valve is threaded into the large part of the valve containing the seal. This stem must be removed to replace the seal. I used some cardboard strips to protect the parts and used two wrenches. Be careful to not mar either part.
It may be necessary to use wrenches to remove the valve stem;
protect both parts!
Here the valve stem is partially removed.
17. Once the stem has been removed the old seal can be pried out. If it is really hardened it may chip as you remove it. I have had the best luck with a punch somewhat smaller than the original exhaust stem. It may be necessary to slightly shave the new seal if it is oversized. This will not matter since it is the forward face of the seal that seals the valve. Replace the valve stem back into the body. It does not need to be too tight; just a bit more than finger tight.
18. Remove the cross pin in the fill fill cap. It usually can be pushed out from either side.
Fill cap assembly.
19. Remove the check valve; replace the seal on the check valve.
Fill check valve with the old seal partially removed.
20. Remove the flat seal from the front of the fill cap - this is the seal that prevents leakage from the external tank during filling. There should be a C-shaped wire washer holding the seal in place. While this seal is out inspect the screen in the fill cap and clean as necessary. Insert the new seal and wire washer.
21. Remove the old square-section o-ring from the end cap. This one can be a pain to remove. The best tool I have found is a small cuticle scissors with the curved blade. Once you can get through the o-ring you usually can pry up the rest from the bottom as you go around the fill cap. This seal must be replaced; the old one will probably leak when the gun is reassembled. Lube the new o-ring with a little pellgun oil.
22. Place the check valve back into the fill cap and replace the retaining pin.
23. The first part to go in is the check valve; the longer section goes in first. If you hold the gas tube pointing straight down and drop the check valve in it should rattle into the hole.
24. Keeping the gun pointing down, drop the new check valve spring in. It may take a couple of tries for the spring to fall onto the check valve.
25. Insert the exhaust valve into the exhaust valve body. Hold the gun horizontal and insert the valve body with the exhaust port pointing straight up. Rotate the gun upside down so you are now looking at the part where the grip attaches. Using the lock nut removing tool or an appropriately sized socket push the exhaust valve into place. Make sure that the small hole in the bottom of the exhaust valve remains aligned with the center of the gas tube. It may take a little force to get the exhaust valve past the threaded section of the tube. When it is pressed home you will be able to see the hole in the valve body through the hole in the gas tube.
26. Hold the gun pointing down and drop the lock nut into place. Using the lock nut tool gently start tightening the lock nut. Use a punch through the hole in the gas tube to keep the valve body from turning. Tighten the lock nut firmly but not too tight; it does not need too much torque. If it somehow works loose later it will be easy to tighten.
27. Replace the bolt in the receiver if it was removed earlier. Make sure that the hole in the bolt probe is pointing down directly at the gas port in the receiver. If your bolt still contained the spring and two ball bearings in its body replace those when the bolt is partially inserted.
28. Turn the gun upside down and drop the hammer pin into the bolt. This can take a few tries and the tweezers may help.
29. I like to use a little moly grease on the wear points on the hammer - the lower back end and the upper front end. Not sure if it will matter in the long run but it may save a little wear on the brass tube. Slide the hammer and hammer spring into place.
30. Replace the rear end cap and the two small side bolts.
31. If you like, lube the trigger contact points with a little moly grease. Replace the grip frame being careful to not lose the safety spring.
32. Test for proper operation of the bolt, hammer, and trigger.
33. Replace the grips; it may not be possible to replace the grip screws due to shrinkage of the plastic. If so the grip should be tight enough that it will not move during normal handling.
34. Replace the fill cap. Be careful at the start to not cross thread the parts. Use your home made tool #1 to tighten the end cap. It should not need to be more than hand tight.
35. Cock the gun, fill it, and check for leaks. The exhaust valve may leak for a second until there is sufficient pressure to seat it fully.
When you fill the gun in the future, place a drop or two of pellgun oil into the fill adapter so it will get carried into the gun by the CO2. It is safe to leave full pressure in the gun for extended storage. Some guns will hold pressure for years. Keeping some pressure in the gun also keeps dust out of the valves and will help prevent leaks.