gamo cfx losing power fast

[shady816]

i recently had my 08 gamo cfx at pyramyd air for gas ram install got it back and was amazed at how powerfull it was as well as consistently accurate after a few hundred pellets the sound started to change and was getting very inconsistent assuming the power or fps is dropping due to pellet impact is creeping down the target almost 8 inches now in one week inspected breech seal front looks a little rough any suggestions i saw a fellows post about moded rotery breech and heavy duty seals any help on how to get would be very awsome.

[kiwi]

Has the cocking force changed..."lessened"
If so it could point to a leak in the ram...

Pete

[shady816]

the cocking force seems to be all there .i have not noticed it getting easier it did get harder after gas ram was installed and this is speratic behavier when it shots with full force it will crack pretty good and the shot will be right on. then it will go into a string of several shots that sound like duds and will shot really low and i am sure somethings wrong for this gun would drive tacs before and another note is this gun would go sonic with light pellets before and now it never does even with pba. i think it is going to need new seals and a good tune or something in there is not wright just do not know what and thanks for looking and responding any suggestions would be great or even any good mod ideas that have worked for others.

[Gene_SC]

Your rotary breech o'ring may be bad. Lay a piece of thin tissue over the breech after you cock and load a pellet. Shoot it and see if the tissue blows off.

[shady816]

thanks gene for the reply and I will try this when I get home today I have pretty much convinced myself that I am going to break this gun down tonight and give all pieces a thuro inspection, something here is not correct I suspected breech seal for it started to feel like something was rolling like bearings or something when opening breech and would get really hard then it would suddenly get extremely easy to open for several rounds. last nights inspection of the muzzle side of the breech seal showed flaky pieces but was intact. another question is there a seal rubber oring or piston rings located on the piston itself inside that could be having blow by causing the gun to perform poorly I just do not seem to get the performance that many others with the same gun seem to be getting so ether they are exaggerating or I got a lemon yes it did perform well for the first month or so of ownership then went down hill and pa tech's claimed the inconsistency is the nature of a spring piston gun and the gas ram would give me less deviation in fps resulting in better performance not more power just more consistent and that it was for the first week after getting it back. thanks again gene for replying and here is a little about myself  I am a mechanical engineer located in Virginia and I pride myself on being as precise as I can and when something doesn't work I normally tear it apart and make it better and I am just about there.

[RedFeather]

Could be they cut that big O-ring in the rear of the cylinder. From what Charlie and Gene have posted earlier, it's easy to have that one roll off the groove when re-installing the tap, as well. My guess would be that PA might have screwed it up when they installed the ram.

[shady816]

thank you for helping i will be disassembling the gun this evening and will post my findings. i will need to locate both breech seals and order so any help on brand name and part numbers would be wonderful, preferably seals that are better than stock after reading a number of post accross the net about them not holding up after gas ram install also would like to go a little deeper while i am in there and replace the piston seal with better as well any suggestion anyone. thanks again this forum has wonderful post that have explained a number of issues that i have seen with this rifle.

[RedFeather]

Check here in the library or Google "CFX breech seal" to find Charlie's helpful hints on working on that breech.

[shady816]

thank you for the replies but i believe i have found the problem i am not gun smith but have rebuilt a number of engines in my time and this does not look correct the piston seal or what ever it is called has a large ding almost cracked all the way now what causes such a thing. i can see the meaning now for deburring this thing has edges sticking into the tube that are razor sharp i have attached some photo's hopefully of the piston seal.

[Gene_SC]

Glad it is a piston seal that went bad.. Get a new Apex seal from JM and you will be good to go.

[shadow]

Yup that there will cause a drop in power and accuracy. :0 Ed

[shady816]

thank you all for the info I just order the Tesla seal from a place in MD I think is airifleheadquarters micrometer read .995 every time which matched the gamo sizing should I replace breech seals while it is apart I need to do some deburring this thing is a mess and i could use some more tips on appling moly and such if anyone would like to share some secrets.

[LongIslandArcher]

Just make sure that whatever might be up the compression chamber that caused the seal to deform like that is no longer there.

[RedFeather]

So much for PA's installation. (They did install the ram, correct?) Any other tuner would have deburred the gun first.

[LongIslandArcher]

Not sure if PA would have needed to pull out the piston sleeve with the piston in order to install the gas ram.  Maybe the increased power blew out a seal that was already on its way to failiing.