ALERT-----GAMO AND THE NEW TWO CROSS PIN ACTION- and the effect on the GRT-4G



Author Topic: ALERT-----GAMO AND THE NEW TWO CROSS PIN ACTION- and the effect on the GRT-4G  (Read 8863 times))

Offline CharlieDaTuna

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Gamo has introduced a change in the action beginning the first of the year in some of their guns. In the future, I will be referring to the new action with the two pins as the GENERATION II ACTION or GEN-II.

 The new GEN-II action has two cross pins instead of the single cross pin that we are accustomed to. The new front pin retains the spring or IGT while the rear pin holds the trigger block in place. See the picture showing the two cross pins and their location. (A) in the picture is the sear and (B) is the rear cross pin. The cross pin marked (C) in the front is the new addition.

I believe there was good reason for Gamo making this change and that is that it was very hard on the trigger block and the extremely high impact that had to absorbed at the rear of the gun.  A good manufacturing call by Gamo.

 The advantage as far as the GRT-4G trigger installation is concerned is that you no longer need to compress the spring or IGT to remove the rear cross pin. Just simply push the pin out. The rest of the installation procedure for the GRT-4G trigger is the same as the original action.

I have not yet seen one of the GEN-II actions but dis-assembly of the gun once the trigger block has been moved is going to be different. The spring or IGT is held in place by the front cross pin. The cross pin blocks a washer that holds either the spring and spring guide or IGT in place and will be under pressure. You will need to make a special tool to span each side of the front pin and to compress the washer and spring or IGT enough to take enough pressure off of the cross pin to push it out to remove them. Once the pin is removed, everything should back right out.

Again, I have not seen the innards of the GEN-II but it will have a different spring guide and possibly a bit of a change in the top hat to offset any coil bind if necessary. This is an advantage because I believe that they can now be TurboTuned again using a fitted Delrin spring guide that will be much easier to machine. Ed or Gene should know as soon as they get one and make a tool to open it up and perhaps advise us.

I have already updated the installation instructions and the can be viewed by clicking the link below and they will also be in the library as soon as the kinks, if any, are worked out.

Click the links below to view the installation instructions.

http://charliedatuna.com/airgun_docs/GRT%204-G%20install%20NEW.pdf

http://charliedatuna.com/airgun_docs/GRT%204-G%20install%20NEW.doc

Below is the Tuning Guide

http://charliedatuna.com/airgun_docs/GRT-4G%20tuning%20supplement.pdf

http://charliedatuna.com/airgun_docs/GRT-4G%20tuning%20supplement.doc

A special thanks to Deeder here on our forum for the photos of the action.
« Last Edit: February 10, 2013, 09:42:36 PM by CharlieDaTuna »
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HOME OF THE GRT-III --- GRT-4G TRIGGER --- CBR TRIGGER
http://charliedatuna.com/GRT-III%20Trigger%20New.htm
http://www.charliedatuna.com/GRT-4G.htm

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Offline Bradman01

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Very awesome write up, Bob. The CDT trigger is the highlight of my rifle so far and thank you for the website and for the work that you have done here and on your triggers.

My gun is a Gamo Whisper Fusion Pro .177, that I like very much, but have been disappointed in some ways.

 I posted the question here about taking off the plastic piece on the back of the rifle then I called Gamo and they told me to get some vice grips and force it off.  No need to remove the first pin.  Again, I missed this the first time around.  :-)

After removing the first pin, the work was a piece of cake, the plastic piece was literally made around the first pin and it came out with no problem as well as the trigger group.  Well machined work. 

To fabricate something to work around the second pin, I took a spark plug socket and hooked it to a 1/2" attachment.  Then I attached it to my "C" clamp on my home made spring compressor making sure that it would line up perfectly.  I unattached each thing and locked the spark plug socket and cut slots on each side the depth of the socket and checked it with the pin in the Gamo.

I permanently attached it to my C clamp and it worked perfectly.  Wish that I had read this first, guess that is why I am a newbie.

Thank you,

Brad
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Offline BurgerTime

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I bought a Gamo Silent Cat a couple months ago. After reading this I was sure that my Gamo would have this new 2-pin action, seeing as I bought it so recently, making it very easy to install the CDT trigger. When I opened it up to do the trigger upgrade the action didn't look like the 2-pin action shown in the picture. There was only one pin. Has anyone else seen the old 1-pin action on newer Gamos? Did they switch back to the old design at some point or did they just send me an old one that's been sitting around for a year plus? Looks like I'll be needing to put together a spring compressor...
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Offline Datasponge

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I bought my silent cat a couple of months ago  (6-8 weeks ago), and mine also has the single pin design.  I don't know the build date of my gun, however - so possibly it was older stock on the shelf.
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Offline BurgerTime

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Ok well at least now I know that I might not be crazy. I watched a really good GRT-4G install video where they used a spring compressor using a scissor jack. It looked like a really great idea and a lot cleaner than sawing up C-clamps so I think I'll put together something similar.
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Offline OleTomCat

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The Silent Cat is an older design that was around before the new two pin design.  I am sure that when they run out of the old stock parts the newer ones will have the two pins.
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Offline N6CRV

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Hello, what I made to use as a spring compressor and worked really good. Is a clamp used for wood. It is the kind that you screw onto 3/4" pipe and can make it any size you need it. One end has a screw clamp and the other end you slid up or down the pipe to what you want to clamp. I covered my pipe with tape as I did not want to scratch my gun. You lay the action on the pipe then I use a hose clamp around the barrel after I put tape where I want the clamp. Then just slide it up to the end with the screw and compress the spring. I have had to put a socket in front of the screw clamp if it was to large to fit into the spring tube. Works good and you can use it for wood working.
Don
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