If you would like a better trigger and don't mind making a few minor mods to your gun, here's a proven design that is easily adjustable for engagement, weight and over-travel.

The front and rear blocks are 1/4" aluminum and the side plates can be steel or aluminum. I used 01 tool steel for the moving parts as I wanted to harden the contact surfaces. The only really critical dimension is the position of the sear tip at the top. It has to intercept the Crosman sear block (140-17) and hold it near the at rest position. In my gun the sear block moves a few thou to the rear on the first pump which makes the intermediate trigger lever come down into contact with the upper tip of the trigger(shown in the first pic).

The 3 adjustment screws are 6-32 set screws. Suitable springs can be found at a hardware store. Depending on the trigger spring, it is possible go down to a couple of ounces pull weight with reliable function, but I don't recommend it. A pound or two is plenty low for a field gun. Since this is a 2 lever trigger, it is insensitive to the load on the sear, so the number of pumps makes no noticeable difference in the pull weight. At least on my gun it doesn't. Don't go too low on the trigger engagement overlap at the upper tip of the trigger. In the 1st pic it looks like it is near zero, but that was a mistake on my part when I was setting up for the pictures. 0.015" is low enough and if the surfaces are flat, square and highly polished, it will break like glass. I don't lubricate my trigger as it just attracts dirt. Running it dry does not hinder it's performance at all.

The trigger housing is attached with 8-32 screws to the gun's plug pin(140-30A)which has been drilled and tapped and to a drilled and tapped hole in the tube as shown. The tube thickness will allow about 2.5 threads which has been adequately strong in my gun.
I believe the front mounting hole could be placed into the small tube plug(140-24)if you make the trigger housing mounting dimensions a little longer forward. This wouuld allow a normal depth tapped hole
The side plates are held to the blocks with 4-40 flat-head machine screws. The back side plate is tapped and the front side plate( not shown) is countersunk for the screw heads. The blocks are clearance drilled for the 4-40 screws. Four is enough. I got kind of carried away.

You have to remove the factory trigger, safety and inlet the stock to accomodate the trigger housing. I didn't put in a safety, but it should be pretty simple to add a trigger blocking type with a release lever extending down into the trigger guard opening and I recommend you do so. Have fun. Be careful.

POWR

would it be possible to locate the forward screw into the sleeve that the barrel mounts to?
no need to thread the tube and more meat for threads?

Really like this as it will make the tigger more manageable at higher pump strokes.

Have you looked inside a 1400 trigger pack? maybe do the same for them?

Walter....

That should certainly improve what is about the only weak spot on that gun - the simple trigger that gets harder to pull with more air pressure. You've done a nice job with the design. Cudos!

"but I'll be needin' that gun, fer squirrels and such."