Gamo .177 CFX Tune Up
1. Pre testing
2. Replace Gamo Trigger
3. Test new GTX-II trigger
4. Get rid of stock rub on barrel
5. Center cocking lever on muzzle brake cocking lever putting side pressure on barrel
6. Drill out screw holes in stock forearm for a straight pull into receiver
7. Replace 4x, 50 yard scope
8. Test new 4-16x56 Leaper scope
9. Bad sound main spring broken
10. Disassemble rifle
11. All dowel pins are straight, not taper pins
12. Get custom seal
13. Get custom spring
14. Get custom spring guide kit and thrust washers assembly
15. Get 6x1.5mm o-ring
16. Get 22x1.5mm o-ring
17. Smooth trigger feet and receiver opening
18. Debur receiver and trigger edges with needle files, hone with diamond stone
19. Finish and polish custom spring ends
20. Check the barrel crown
21. Debur end of barrel, muzzle brake attachment polish crown
22. Polish cylinder wall checked good
23. Polish cocking shoe
24. Debur and polish piston seal button radius button
25. Install new custom seal soaked in hot water dry coat surfaces with moly/graphite - install
26. Molylube cylinder - plastic modelers paint brush
27. Install loading port with new 22x1.5mm o-ring
28. Install 6x1.5mm o-ring barrel-loading port seal
29. Trigger seer hone & polishing
30. Cleaning & lube trigger assembly
31. Velocity tar main spring lightly
32. Bore clean used ZEP citrus cleaner full strength
33. Adjust the cocking lever locking assembly centered to muzzle brake
34. Muzzle Brake get rid of rattle with grease cushion
35. External Lube
36. Final testing
I would like to thank Lon for the use of his pictures.
I have a broken main spring. Notice how the coils are wound together.
Spring and parts reference.
You have to get the piston seer out of the way.
The removed trigger assembly.
Smooth these areas with a fine stone. Dont change the angles!
Where the trigger assembly belongs. The burrs made the trigger assembly hard to remove. Gamo must have installed the trigger with a hammer.
The original CFX disassembled except for the GTX-II trigger blade.
The new spring from:
Also you will need lube:
And this is the new seal that I used:
The spring dressed and polished.
Rich from Mich tune kit. I used the spring guide with the thrust washer / tophat assembly.
The old seal. Remove the old seal and radius and dress the sharp edge of the dovetail.
Picture of different seals.
The piston before I started to debur the interior and polish the tailing edge.
Deburred and polished.
End of the barrel with the muzzle brake removed.
Removed muzzle brake with a slot cut into three-quarter inch board just large enough to fit over barrel. Tapped off with hammer.
Gamo faced the end of the barrel but left a rolled burr in the barrel.
View of rifling.
Notice the rifling is below the barrel crown.
Barrel chucked up in the lathe.
Removing the facing burr.
I went on to radius the barrel crown and polish. I couldnt get a good picture but the barrel crown had all sorts of little burrs around the perimeter.
Polish the cocking shoe.
Lengthened the stock one half inch and filled the butt cavity with Great Stuff foam.
Interesting side note. This changed the recoil finish. The rifle used to finish to right before the foam and straight up after the foam. More testing required.
Shot this group at 25 yards, sitting with front hand supported, Kodiak pellet, 24 shots
Back together again.
Rich from Mich - spring guide kit
Steve from NC - GTX-II trigger blade
JM piston seal
Scope mounts - Accushot High Profile Full Length Integral Mount RGPM2PA-30H4, 30mm
Scope - Leapers 4-16x56 30mm Range Estimating AO Mil-Dot Illuminated Full Size
Expect about six hours to do the work. Finding all the parts and pieces was not included.
You will want a spring compressor for spring removal and install. I used my lathe for the spring compressor.
Needle files make removing the burrs easier. I used a diamond hone and Arkansas Whet stones to polish around the milled/stamped receiver openings.
Debur and polish everything that moves. Be careful of the burrs, they are sharp and can cut like a knife!
What has been done to my rifle is only a suggestion, it is not a Bible. Work on your own rifle at your own risk.