Anyone ever shorten a 1377

Anyone ever shorten a 1377

v30
Joined: January 15th, 2010, 5:37 pm

January 8th, 2011, 10:47 pm #1

Just curious if anyone has ever shortened one? I was thinking that an inch or 2 shorter would be ideal. I guess it would be a bit harder to pump but I could live with that. What other hurdles would you have to overcome?
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Joined: September 6th, 2006, 3:27 am

January 8th, 2011, 11:36 pm #2

is a bit shorter.

A Benjamin 130/137 is a lot more compact.

Both are long out of production.
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Joined: April 1st, 2009, 3:18 am

January 8th, 2011, 11:53 pm #3

Just curious if anyone has ever shortened one? I was thinking that an inch or 2 shorter would be ideal. I guess it would be a bit harder to pump but I could live with that. What other hurdles would you have to overcome?
Sure did. Was trying to make a SSP (Single Stroke). I didn't really work out as a single stroke though. It would still shoot about the same velcity, but was much shorter.

I had the front valve half shortened (via lathe) and then made a shorter tube. The issue why a single stoke wasn't going to work is that making things shorter put things kinda' to proportion/scale, or pump stroke to voulme ratios stayed about the same. The pistol did end up about 4" shorter. The trigger frame screw location in the front was removed (files and such) and a new one was drilled back in the trigger guard area, as it had to be.

Looked really awsome with a long steel breech on it. Also, It was rather loud and in .22cal

Picture of it is long gone now. Been a few years ago.

In the end, yes it can be done.

"Well, I thought it was a rabbit but it turned out to be Bear Grylls in a rabbit hide."

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Joined: June 5th, 2006, 12:49 am

January 9th, 2011, 1:07 am #4

Just curious if anyone has ever shortened one? I was thinking that an inch or 2 shorter would be ideal. I guess it would be a bit harder to pump but I could live with that. What other hurdles would you have to overcome?
[/IMG]

The example is a .30 I built based on 13xx type pump and valve,
with extended valve volume.

Cutting off the tube past the valve stem and adding a hammer & custom trigger frame and
breech would be one way of reducing length without losing power.

EDIT: You'll see a white acetal cap just in front of the scope mount. Below this is
the transfer port - giving an indication of how far back things are.
Last edited by CO222 on January 9th, 2011, 1:09 am, edited 1 time in total.
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Joined: April 1st, 2009, 3:18 am

January 9th, 2011, 2:20 am #5

See, I am currently in the process of doing a 9mm pumper project. Waiting for some more items to arrive...

The base of this pumper is the Benji valve with extended volume big time. Hoping to get at least 40 ft-lbs with Eunjin pellets. We'll see. I'll be happy with 30.

Are you shooting shot? Please tell more. I remember a little about that build a while back...

"Well, I thought it was a rabbit but it turned out to be Bear Grylls in a rabbit hide."

Last edited by Duane30 on January 9th, 2011, 2:40 am, edited 1 time in total.
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Joined: November 20th, 2006, 11:42 am

January 9th, 2011, 11:43 am #6

Just curious if anyone has ever shortened one? I was thinking that an inch or 2 shorter would be ideal. I guess it would be a bit harder to pump but I could live with that. What other hurdles would you have to overcome?
I'm referring to this plastik thing, that attaches the pump cap to the pumping linkage. May be it could be shortened without any loss.

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Joined: April 1st, 2009, 3:18 am

January 9th, 2011, 4:19 pm #7

...if you don't mind pumping to 20-30 charge the valve.

"Well, I thought it was a rabbit but it turned out to be Bear Grylls in a rabbit hide."

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Joined: April 1st, 2009, 3:18 am

January 9th, 2011, 4:36 pm #8

Just curious if anyone has ever shortened one? I was thinking that an inch or 2 shorter would be ideal. I guess it would be a bit harder to pump but I could live with that. What other hurdles would you have to overcome?
Just thought about a single stroke idea that can really shorten a 1377. A new will need to be made due to the front screw hole in the frame.

1. Cut the valve down to just about an 1/8" or 1/4" past the exhaust stem head. Could even cut the rear valve half down a bit and shorten the exhaust stem too.
2. Put an o-ring aroun the valve.
3. Cut the tube to the proper length as to still allow the factory amount of pump travel.
4. Convert the exhaust stem to an external spring type holding the spring in place via e-clip.
5. The frame forward screw will need to be moved up in the trigger guard well area in to the tube (like I did on mine) just right behind the valve (so striker doesn't hit it).

Should work. This I may even try some day. The idea with a single stroke is to have optimum travel of pump volume and compress it down to a really tight space to create high pressure. Very little volume to pressure single strokes are. Since they are for TARGET shooting, energy isn't a requirement, i.e. killing things.

"Well, I thought it was a rabbit but it turned out to be Bear Grylls in a rabbit hide."

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Joined: April 1st, 2009, 3:18 am

January 9th, 2011, 9:41 pm #9

Okay, after some thought and being a dull Sunday... It was decided that it is possible to make a 1377 single stroke valve without any machine tools, so I did.

Stroke will be the same as stock 1377, but only one stroke. Open up after the one stroke will dump the air (Daisy-like). Took a stock 1377 valve and cut it down; used a Benji 39x stem. All "machine work" was dine using a drill and carbon chisels and my trusty Swiss-Army knife chisels.

To protect the valve port, a rubber faucet washer was put inside, a screw through that with a nut on back. The remaining screw protruding was used to chuck in the drill to spin it.

The Benji stem got the brass removed. One stroke will really compress into a very small-tight space.

The pump head conical shape allows good movement for the exhaust stem to "pop" while allowing a small amount of trap space.

The rear of the valve has been counter sunk drilled to put an o-ring in and a steel washer on top of that. This was done to maximize the amount of air going in to propelling the pellet; the stock valve designs will waste a little air/pressure out the back of all Crosman valves - this stops that. I have yet to put a groove around thestem head so an e-clip or c-clip can attach to put the spring on. This is the general idea on the valve. I will soon slap a pistol together that is much shorter in length, one stroke, target inspired pistol. Who knows, this may surprise me!





"Well, I thought it was a rabbit but it turned out to be Bear Grylls in a rabbit hide."

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Joined: November 5th, 2008, 8:23 pm

January 10th, 2011, 3:11 am #10

Oh man---I hope this works for you---please keep us updated with pics and details!!!!!--nt
Last edited by ray1377 on January 10th, 2011, 3:12 am, edited 1 time in total.
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