.177 Gamo silver shadow accuracy

[Magnum]

I'm the second owner, best I can tell it was purchased new around Sept last year 08 and first owner shot about 1.5k pellets so it looks new.. I have tried 2 different scopes and mounts on this one and cannot get the accuracy I'm looking for.. best I can do is 2" at 10 meters! It has excessive grease and the spring looks to be kinked from the part that I can see. Have also noticed diesel effect and smoke, I fired about 100 shots and still seems to still be dieseling,  it is  loud, vibrates alot and twangs . Another thing  I have not seen before or heard of anyone doing this, but ...The metal next to the barrel breach seal seems to have a pressure wear mark on one side only so thinking this may need to be lapped so no bias, not sure if this is a good idea?
 
   The crony said I have 845 av. fps and  a 32 fps spread on 15 shots .using the same pellets in an identical except black shadow I get 895 av. fps and 20 fps spread on 15 shots.
 My plan now is to possibly try my first ever major tune ( I see nothing to lose and always wanted to give it a shot).   Well it was a good idea untill I discovered I cannot find any good info or links on what to do:( Any suggestions welcome:)  I would really like a maccari spring, Guide, washer and possible telsa seal and according to the web site if not mentioned then he does not have it! I do not want to disassemble, make a spring compresser or order anything like GRT 111 trigger get a camo paint job etc.. until I know I can get what I need and feel comfortable with this project.
 I need help with where to buy what I need and what to be aware?  All advise and help appreciate, Tony.

[fsdanlie]

My gamo hunter sports had a bad bend on the spring from over lube and dieseling to much and ordered the e3650 spring and seal and used only velocity tar on spring guide and top hat and outer spring and molyed the back side and piston seal and outer piston with moly and what a difference it made,no twang just a thump.Your gun probably takes the new tarantula spring ,due to 38 ilb.cocking force.

[Gene_SC]

Tony, JM does not make a custom guide for the tarantula spring. The tarantula spring has oversized I/D so the stock metal guide will not work well. The 3650 is a great spring as well and will accept your stock metal spring guide. Your smoke is probably from the seal passing lube. Use a small tesla seal for a replacement. I suggest you cross hatch the action bore as well with a 400 grit brake hone. Good luck

[Magnum]

Gene, thankyou so much for info.. I found the spring "The E3650 Ultra spring" will I need a Washer ? I assume this is the telsa seal you mean,  it doesn't say small ..  http://www.airrifleheadquarters.com/catalog/item/251485/2325552.htm  ?  I will document as I proceed and post results. I think this will be fun and at least only 2 things can happen, it will be either work or not.. hehe:) Thanks again,Tony

[Magnum]

I am still unsure if this is an issue or if it is maybe a common thing and therefore is not an issue?  "The metal next to the barrel breach seal seems to have a pressure wear mark on one side only.. so thinking this may need to be lapped so no bias, not sure if this is a good idea? "

[Magnum]

Now that I look at  my picture again  it  is not really that clear!! the wear pressure point is the shiny parts on the top and to the right side:) I am curious if anyone else has seen this before?

[Magnum]

Well I am further along and now waiting for my GRT 111 trigger and a JM spring and seal to arrive.   I am sort of learning and winging it as I go, I gave up trying to find info on the net although before I did stop... I saw where someone had suggested  thrust washers, making a new guide and making  brass tophats!
        The question I am asking now is does it make that much difference,  do  I really need to worry about  all this and if it is a big deal where in the heck do I buy such things?   If  I  just use the original oem guide and hat and still be ok ?  I hope I have not opened a can of worms for myself here!:) Tony.

[Gene_SC]

That seal is good Tony, and I see allot of the barrel breech shinny spots where the barrel breech looks like it is scuffing against the action. My only recommendation would be to check your lockup. Also make sure there is no play between barrel breech and action forks. You can tighten the screw if it is a common head screw. Most of the time if the barrel does not have a bit of tension on it then that means it could be worn there. So try and tighten the breech screw. You may need an impact screw driver and hammer. I buy stainless steel washers and cut them down on my lath to fit inside piston. Also it does not hurt to polish ends of spring.

[Magnum]

Gene, Looks like the barrel lockup is weak and not as strong as the other gamo shadow I have ..its easier and lighter to break the barrel on the initial cocking of the action so I will have check angles on the latch bolt, see if I can make spring loaded catch hook up a bit tighter. I checked the barrel pivot screw It does appear it could be abit tighter but otherwise in good shape seems snug:) I will be polishing spring ends and tackle the stainless washer when I get to that part. Thanks again for your generous help, Tony.

[larspawn]

Tony, your breach seal looks a bit chewed up too.  I smear a bit of pellgunoil on my seals to keep them happy.  Kind of like lip balming them occassionally.  Keeps them nice and supple.

[KenPCPilot]

Sorry to tell you after your purchase but I would not expect much better accuracy results.  I purchased one brand new and it was a terrible shooter.  Multiple issues with the gun.  

1. Some pellets fit so loose in breach they would fall out if I was not careful
2. Horrible spring vibration "twang"
3. Very light weight.  I have more trouble holding on site with a light gun vs a heavy one.
4. Never found a pellet that grouped well after several hundred shots.

Other than the Gamo Whisper this was the worst airgun I have ever shot.  The only good point was the scope that came with the gun.  It is a BSA 3x12x50.  I sold the gun and kept the scope which remains on of my favorite low power scopes.  I rarely have to rezero once sited in with a particular pellet.  Hope someone can give you better advice than I can.  I really took a beating since I paid about $300 brand new and sold it for $170

[Magnum]

I am always sorry to here about a bad gun from the factory and that you had to take a hit like that!:(  Sometimes exchange is the way to go.
         I felt that I had nothing to lose, so I pushed on with this experiment and fortunately got great results ...  see post here  http://www.gatewaytoairguns.com/airguns/forums/thread-view.asp?tid=19621&posts=5&highlight=progress&highlightmode=1#M158119  After this post I continued to work on it and have improved it even more:), with some soft scub work to the barrel,  some careful polishing to snug up the barrel lock up latch and a new breech seal.
          I had fun with my tune and it is now an accurate shooter and certainely a lot more fun.  I will also add that it is very sensitve to pellets and anything below 8.2gr is no good! The best ones to date are the  rws meisterkuglen 8.2gr and rws supermag 9.3gr  both wadcutters,  will make a single hole at 15yds all day long.  Tony.