Crosman 13X/13XX mashup

[WestCoastFranky]

This is a build that I'm working on.  It's a combination of a Crosman 137 and early Crosman 1322/1377s with the rear cocking mechanism.

The pump tube and grips are from a rear-cocking 1322 with a plastic breech.  The steel breech and barrel were from a rear-cocking 1377.  I adapted the valve from a 137 with a blowoff style valve because I was wondering what the modern 13XX would have been like if they had used the blowoff valve from the Crosman 130 series of pistols.  The valve is shorter so I had to add an extension to the piston shaft.

I polished the sear block from the 137 to make the trigger lighter and smoother.  At three pumps the trigger is 2.5 lbs and at 8 pumps it is 3 lbs.  I think that works for a pistol but it's a little heavy for a shoulder mounted gun.  I have gotten a 13X pistol down to 1.5 lbs by polishing everything in the trigger train so that is what I will be doing next to the trigger.

The stock is made from 3/4" aluminum tubing and 10-24 threaded rod.  The threaded rod passes through the tubing and is held in tension between links while the tubing is held in compression between the links so the stock is very stiff.



To mount the stock to the gun, I machined a replacement end cap that accepts a 10-24 threaded rod.  The replacement end cap is held in place by the frame mounting screw that passes through the pump tube and is threaded into the breech end cap. 



The 3/4" tubing registers onto the back end of the pump tube making a very rigid connection.



This is an exploded image of the end cap assembly.  A barrel screw passes through a link and is threaded onto an end of the threaded rod at the link.  The threaded rod passes through the link and tubing and the other end of the threaded rod is threaded into the replacement end cap.  The tubing is captured between the end link and the replacement end cap so that when the barrel screw is tightened the tubing is held in compression between the link and the replacement end cap while the threaded rod is held in tension.



I like the stock design for a couple of reasons.  It's easy to make the parts, nothing fancy and I don't have to cut any large diameter threads.  Someone can do this with nothing more than a hacksaw, a hand drill, and some files.  The design is also easily changed for length etc. simply by cutting the threaded rod and tubing.  The stock is super stiff, it's a lot more solid than most frame style stocks.  Finally, any type of material can be used for the tubing as it's held in compression and not in tension.  I plan to try some wood and maybe some Kirinite as the material for the compression members.   

The scope is a 2X20 BSA Edge pistol scope.  I like using pistol scopes on carbines because I don't really need amplification but I need help focusing.  The Edge is inexpensive as scopes go and I can mount the scope so that I can have access to the breech.  My next project is to make a scope mount that mounts directly to the barrel without having to use an intermount.

And for those of you who bemoan the loss of yet another 137 and 1377, these were basket case guns with a lot of corrosion.  I buy the guns on eBay that nobody wants because of their rough shape, no guns in fair or better condition were sacrificed for this mashup.  Since my accuracy needs are modest, one MOSC (Moment Of Soda Can) at 15 yards, I give new life to worn out or otherwise abused guns.