Maximum power of tuned cfx in .177 cal

[striker_12b]

what would be the maximum power(footpound) that can be attained by tuned gamo cfx .177  with maccari spring ,seal and custom tophat?and the pellet to be considered 8.3 gr

[Gene_SC]

Sankar, I have tuned many CFX Gamo .177's. The average is around 825 to 870. Very few chrony out past the high number. I am using for all my chrony testing Gamo 7.9 gn round nose pellets. Due to the rotary breech o'ring there can be air leaking past it. Even on a new CFX. It is an inherent problem.

Hope that helps

[RedFeather]

Not so much a problem as it is a design limitation. While the CFX may lack in raw power, it appears to make up for it in accuracy. I don't think there are any tap loaders (flip type or rotating) which shoot in the 900's. If you need more power and like the underlever, maybe a Diana 460?

[Gene_SC]

That is for sure Red, because I still have two CFX's and even though they do not shoot in the 900 fps range the sure are very accurate. I really like the smooth shooting cycle they have.

[striker_12b]

Gene
       what is the best oring size/spec  that fits airtight for the rotatory breech?

[Gene_SC]

Check this out.

http://www.gatewaytoairguns.com/airguns/forums/thread-view.asp?tid=12320&posts=25&highlight=CFX Rotary&highlightmode=1#M112357

http://www.gatewaytoairguns.com/library/Gamo%20CFX%20Breech%20Seal%20Repair_LateModels.doc

[striker_12b]

Thanks Gene
                     Any information on Piston buttoning over cfx and its results?

[mze]

Pellet size has much to do with power and velocity.

  All tests were conducted at 6000 feet altitude.

Case One

 CFX lube-tuned and fitted with a 700N gas ram had this result.
Using H&N Field Target 8.6gr 4.50mm pellets averaged 790fps = theoretically ±932fps at sea level.
Using JSB Exact 8.44gr 4.53mm pellets averaged 695fps = theoretically ±820fps at sea level.
In agreeing with Gene on leakage past the rotary breech block, I doubt that the theoretical sea level velocities will be achieved. Note the velocity loss when using a tighter but lighter pellet.
Going to JSB Exact 8.44gr 4.52 pellets increased velocity by an average of 25 fps.

Case Two
CFX Lube tuned and fitted with new piston and breech seals and Global Tarantula spec mainspring
H&N FT 8.6gr 4.50mm pellets averaged 744 fps.
The piston and seal, top hat, mainspring, and rear spring guide were put in a Bam B19 break barrel Gamo clone giving these results
H&N FT 8.6gr 4,50mm pellets averaged 838.3fps
Diabolo Master 8.23gr 4.50mm pellets averaged 859.6fps
Bearing in mind that bore size has a material effect on velocity, this illustrates the velocity loss experienced by the CFX rotary assembly.

Case Three
CFX lube-tuned and fitted a 650N gas ram had this result.
H&N Field Target 8.6gr 4.50mm pellets averaged 752fps.
JSB Exact 8.44gr 4.53mm pellets averaged 640fps.
Diabolo Master 8.23 gr 4.50 pellets averaged 848fps

Case Four
Gamo Shadow RSV Lube-tuned and fitted with a 650N gas ram
H&N FT 8.6gr 4.50mm pellets averaged 862fps
JSB Exact 8.44gr 4.52mm pellets averaged 837fps
JSB Exact 8.44gr 4.53mm pellets averaged 813fps
Breech seal not so good.
This client is now achieving a consistent 830fps using JSB Exact 8.44gr 4.52 pellets at 4000 feet altitude.
The gun is smooth and sounds like a PCP.
He prefers shooting the gas rammed Gamo to His Weihrauch HW100 PCP!
My own CFX using the same gas ram, piston and piston seal.
H&N FT 8.6gr 4.50mm pellets averaged 746fps
JSB Exact 8.44gr 4.52mm pellets averaged 720fps
JSB Exact 8.44gr 4.53mm pellets averaged 695fps

I now recommend my clients to use JSB Exact 8.44gr 4.50 or 4.51mm pellets for accuracy and least pressure loss at the rotary breech block.
I also recommend that they try all pellets in the 7.9gr to 8.0gr range to establish what the gun likes for accurate results.

I have not yet found a CFX which has not had the large o-ring on the rotary breech block damaged.

I have a CFX waiting for a full lube-tune, trigger and gas ram which had never been opened. The front seal on the rotary was hammered flat. I replace this seal with stacked o-rings. The rear 0-ring had been damaged on assembly and had a segment sliced off. The piston seal was damaged in at least 20 different places during assembly. It is no wonder then that this gun chronied at 530fps. This not what the owner expected when he bought the gun.