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.pdfhttp://charliedatuna.com/airgun_docs/GRT%204-G%20install%20NEW.doc
Below is the Tuning Guidehttp://charliedatuna.com/airgun_docs/GRT-4G%20tuning%20supplement.pdfhttp://charliedatuna.com/airgun_docs/GRT-4G%20tuning%20supplement.doc
A special thanks to Deeder here on our forum for the photos of the action.