CFX rotary breech
Select Gate
READ GTA FORUM RULES BEFORE POSTING
GTA Forum Help Desk
GTA Announcement Gate
Dealer Area
GRIP
AirgunWeb Airgun Videos
Airgun Repository of Knowledge
Vendors and Vendor Videos
AirGun Expo 2021
Airgun Expo 2022
Contests and Giveaways!!!
Welcome New Members
In Memoriam
GTA Contributing Members
Shot Show Videos
Hajimoto Productions
Airgun Detectives
Air Gun Gate
BB Guns and Such
"Bob and Lloyds Workshop"
American/U.S. Air Gun Gates
European/Asian Air Gun Gates
PCP/CO2/HPA Air Gun Gates "The Darkside"
Air Archery
Vintage Air Gun Gate
Air Guns And Related Accessories Review Gates
Hunting Gate
Machine Shop Talk & AG Parts Machining
3D printing and files
Buyer's, Seller's & Trader's Comments
Bargain Gate
Back Room
Target Shooting Discussion Gate
Target Match Rules
Shooting Match Gates
Field Target Gates
The Long Range Club
100 Yard Match
Discussions By States
Welcome,
Guest
. Please
login
or
register
.
Did you miss your
activation email
?
1 Hour
1 Day
1 Week
1 Month
Forever
Login with username, password and session length
Home
About
Help
Old GTA
Gallery
Search
Stats
Login
Register
Advertise Here
GTA
»
All Springer/NP/PCP Air Gun Discussion General
»
European/Asian Air Gun Gates
»
Gamo & Spanish AirGun Gate
(Moderator:
Tpatner412
) »
CFX rotary breech
« previous
next »
Print
Pages: [
1
]
Go Down
Share This!
Author
Topic: CFX rotary breech (Read 1196 times))
rumenmalinov
Shooter
Posts: 70
yes
Real Name: rumen
CFX rotary breech
«
on:
May 21, 2021, 03:45:44 PM »
Hello. I recently bought CFX .177 . I took it apart completely for some light maintenance since The gun started to loose velocity only after two weeks and in addition to the damaged seal, I noticed something that I am not sure if it is reason for concern or not: please review the attached images. What is the part that I have circled in red? Little spring and something like a pin? I don’t have that with my rotary breech, but there is a hole where I think they should go.
Thanks for your assistance
Logged
sofia, bulgaria
Artie
Expert
Posts: 1242
yes
Real Name: Richard
Re: CFX rotary breech
«
Reply #1 on:
May 21, 2021, 04:26:44 PM »
You have a CFX which has a different rotating breech than a CFR. The parts pic is for a CFR so disregard the "extra" parts (spring & pin) as they are not needed for your gun.
The CFX preceded the CFR. The CFR came later and was relatively short lived. The final iteration of the Gamo underlever was the Accu and it has a breech very similar to yours. I have all three versions.
The earliest CFX actually had two varitaions of the breech. The first variation had a very shiny, polished finish, almost like chrome plating wheras the later CFX, CFR, and Accu had a satin finish.
FYI:
Early (2003-2005) CFX:
- Rotating Breech (chrome polish finish): The transfer port o'ring groove is 1.5mm deep, not 3mm deep like newer CFX, CFR, Accu guns.
CFX, CFR, Accu: All mine use the same large rotary o'ring seal: 1.5mm x 22mm (25mm OD) D70 hardness. I installed in my Accu 177 a #017 D70 o'ring (ID 11/16", OD 13/16", CS 1/16") but the breech is really too stiff to rotate with this oring. A 22mm, D70 o'ring is correct for later CFX, CFR, and Accu.
- Small Rotary Breech o'ring (transfer port): Two different sizes depending on manufacture year and breech coating finish (bright chrome or brushed satin)
My CFX, CFR, Accu guns with SATIN finished breech: 1.5mm x 6mm with a 3mm height.
My 2003 CFX Royal with CHROME finished rotary is 1.5mm x 6mm and height is 1.5mm, not 3mm.
Both type (satin & chrome) breech transfer port o'ring are 9mm outside diameter.
Logged
North Carolina
Mole2017
Squirrel Researcher
GTA Senior Contributor
Posts: 2351
Real Name: David
Re: CFX rotary breech
«
Reply #2 on:
May 21, 2021, 05:35:59 PM »
Thanks for the data Richard. I have two older CFX rifles, but I'd have to check the serial number for the date. They are old enough to have the steel triggers.
Logged
Pendleton, SC
Gamo CFX .177 and .22, old style triggers
BSA R10 MK2 .177
Crosman 1377
Artie
Expert
Posts: 1242
yes
Real Name: Richard
Re: CFX rotary breech
«
Reply #3 on:
May 21, 2021, 06:09:40 PM »
I believe all Gamo underlevers preceding the CFR and Accu had the steel blade triggers. I'm thinking the CFR was Gamo's first underlever with the plastic blade (SAT) trigger, aka
"Smooth Action Trigger".
The later Accu also sported the SAT trigger.
The latest version Gamo trigger (CAT) aka
"Custom Action Trigger"
was not released until after the CFR/Accu was discontinued. It also has a plastic blade but with an additional adjustment screw.
The CDT relacement trigger for a steel blade triggerd Gamo is the gold GRT III with two adjustment screws. The later SAT
and
CAT triggers both used the gold GRT IV trigger with only one adjustment screw.
IOW.. steel blade = GRT III, plastic blade = GRT IV.
Logged
North Carolina
rumenmalinov
Shooter
Posts: 70
yes
Real Name: rumen
Re: CFX rotary breech
«
Reply #4 on:
May 21, 2021, 06:33:08 PM »
Thanks for the swift response!
The little seal was completely “shaved” by the sharp edges around the place where the pellets go. I think I did a good job and now it’s all smooth and even. I ordered replacement seal from here:
https://www.ebay.com/itm/294063092843
But I would welcome any other suggestions as long as I can get the order to Bulgaria.
I had spare parts that I ordered with the rifle, but for some reason when installing the rotary something isn’t quite right and the velocity doesn’t go over 700-705fps , the gun initially was shooting around 750. I have polished and deburred I am sure the new O ring isn’t cut. Is there any method to be followed when installing back the rotary?
Thanks
Logged
sofia, bulgaria
Artie
Expert
Posts: 1242
yes
Real Name: Richard
Re: CFX rotary breech
«
Reply #5 on:
May 21, 2021, 06:57:28 PM »
Sounds like you did your homework. Deburring is a must for your gun, good thing you did or the large o'ring will have a nick/cut almost certainly and will degrade sealing capability.
I need to know if you prelubed your gun prior to assembly and
what
you used for lube. Did you install a new piston seal, if so, what brand. If you sleeved the piston or changed/shimmed the rear spring guide how tight were they? I also need to know what pellet you are shooting to attain 700 fps.
Whatever pellet you are using, is the speed a fairly consistent 700-705 fps?
«
Last Edit: May 21, 2021, 07:03:50 PM by Artie
»
Logged
North Carolina
rumenmalinov
Shooter
Posts: 70
yes
Real Name: rumen
Re: CFX rotary breech
«
Reply #6 on:
May 21, 2021, 07:03:13 PM »
New piston seal. The CFX is IGT gas ram. Pellet jsb 8.44gr. I just put VERY thin film of silicone oil on the outer parts of the seal/rotary. Also polished the piston and put very thin film of molly paste only at the tail end. Silicone oil just a drop around the piston seal. That’s it
Speed is consistent but the velocity was much better before it started to drop yesterday and once I opened the rifle I realised the breech seal is damaged. But now I can’t get anywhere near 750
«
Last Edit: May 21, 2021, 07:06:36 PM by rumenmalinov
»
Logged
sofia, bulgaria
Artie
Expert
Posts: 1242
yes
Real Name: Richard
Re: CFX rotary breech
«
Reply #7 on:
May 21, 2021, 08:12:20 PM »
Okay, so you've shot the gun enough since reassembly to know if it has settled in and most detonation has subsided and you know it is shooting @50 fps lower than before?
If the gun is US spec .177, a 7.9 gn pellet should be above 800 fps. The American CFX is 13-14 foot-pound gun (18+ joules). So yes, your gun is shooting slow.
A tight piston seal can lower speed significantly. I have seen that in my CFX with a new piston seal. I had to resize the seal to raise fps.
The transfer port seal can flatten out from the slamming that occurs everytime the piston hits it.
It is always difficult to diagnose something like this without having the gun in my hands but if US spec, you are a 100 fps or so lower than spec if shooting 7.9 gn pellets.
Here are some specs on my .177 CFX (oem):
Mainspring: 35 coils including ends, .118' WD (3mm), .535" id, 9 -15/16" oal, 1.5" preload
Steel guide od = .483"
Compression tube id is less than .997"
«
Last Edit: May 21, 2021, 08:17:23 PM by Artie
»
Logged
North Carolina
rumenmalinov
Shooter
Posts: 70
yes
Real Name: rumen
Re: CFX rotary breech
«
Reply #8 on:
May 21, 2021, 08:25:55 PM »
I know for a fact that this particular gun was made 18j by Gamo. Not the regular 20j . For some reason who knows why. The seller Mundilar.net confirmed with Gamo. Even the seller didn’t know that until I complained. I bought a standard 20j Gamo IGT to replace the factory and the velocity got worse the recoil was horrible too so put back the 18J . So I was shooting around 14.5-15J and it was very accurate so I was ok. And then the velocity dropped, changed the seal, cleaned polished etc but now is not getting back to where it was. The rotary now feels a little kinda of wobbly when the rifle is cocked and I push it with a finger. I don’t know what to think... Until I get the seals I ordered from the link I posted above I guess I wouldn’t know if that’s the issue or who knows what else could it be
If it’s not too much trouble, would you mind to take a picture with the rotary closed and opened? I just want to compare with what I see on my rifle . Thanks in advance
«
Last Edit: May 21, 2021, 08:39:10 PM by rumenmalinov
»
Logged
sofia, bulgaria
Artie
Expert
Posts: 1242
yes
Real Name: Richard
Re: CFX rotary breech
«
Reply #9 on:
May 22, 2021, 07:36:15 AM »
Sorry for the late reply. I will take pictures and post later today.
If velocity worsened with a stronger gas strut it suggests to me that one or more seals is failing to do their job and the highly compressd air is leaking.
Could be a leaking piston seal or the o'rings.
Here are some notes from one of my Gamo Accu .22 underlevers that was initially tuned 2017 and rechecked on Nov 21, 2020:
"RWS SD - 650 fps, RWS Hobby - 700 fps. That's @ 50 fps less than initial tune (2017) so I removed the piston and inspected:
*The russian piston seal had near zero resistence when dropping the piston into the upright moly lubed compression tube. Not enough resistence nor likely a good seal. The ultra thin parachute lip had collasped into seal body, setting permanently.
*One wrap of masking tape around piston seal raised seal od to .990" and improved pressure/vacuum. So I resized an ARH Tesla Custom seal to
.993" (like I did with CFX 22) and fired 40 shots after storing the gun overnight. The new seal should set at @ .990" (like the CFX).
Next day tested with a 2lb weight behind piston. Tighter than CFX piston and now had strong pressure. Next I covered the transfer port with tape and pulled vacuum by pulling a fully depressed piston back. I could not pull the piston back, the o'rings and piston seal were holding strong vacuum. I changed piston seals and power was back to normal."
Something else to consider:
Did you or the owner before you hone the compression tube bore after receiving the gun? If the area around the rotating breech was honed the breech would be looser and leakage would likely occur. A flat (squished) transfer port o'ring may cause a bit more, noticable breech looseness/wobble as well (with the piston retracted). The transfer port seal and plastic breech handle is what maintains tension on the rotating breech and keeps things tight. A worn out plastic handle might do it too if a deep enough groove was cut into it from thousands of opening and closings.
«
Last Edit: May 22, 2021, 08:38:06 AM by Artie
»
Logged
North Carolina
rumenmalinov
Shooter
Posts: 70
yes
Real Name: rumen
Re: CFX rotary breech
«
Reply #10 on:
May 22, 2021, 07:55:34 AM »
Thanks to the reply.
The CFX is brand new, less than 500 shots. I haven’t done any honing. Just took care of the rough edges on the cocking lever slot, trigger and the holding pin at the end.
I have also polished the rough edges around the beginning of the barrel where the breech seal makes contact. But it’s not that much in order to create extra “room” for the rotary to wobble.
I have seen some CFXs have a little “curve” on the opening where the plastic pin on the rotary makes contact which pushes the rotary further up for tighter seal On the pellet when closing the breech. I don’t have that.
I am out but later I will attach images for better understanding of what I am trying to describe.
Thanks for your time!
Logged
sofia, bulgaria
Artie
Expert
Posts: 1242
yes
Real Name: Richard
Re: CFX rotary breech
«
Reply #11 on:
May 22, 2021, 08:46:43 AM »
I edited out my comments on the "curved" CFR since it did't apply to you (sorry) but I added comments on how to test for vacuum/pressure. You are right about the "curve" in the guns that have it and pressure on the pellet as the breech is closed, that is something I failed to mention. I have also heard that curve is suppose to prevent clipping the pellet skirt with the o'ring.
What is still available in Europe (Gamo underlever) may no longer be available in the US market, I don't know.
«
Last Edit: May 22, 2021, 08:55:54 AM by Artie
»
Logged
North Carolina
rumenmalinov
Shooter
Posts: 70
yes
Real Name: rumen
Re: CFX rotary breech
«
Reply #12 on:
May 22, 2021, 02:27:57 PM »
Ok here are few pictures. You can see where I worked around the the barrel and how it looks now. It’s very smooth and no sharp edges. I can’t imagine that I have taken that much in order have now more “room” for the rotary to wobble.
Nevertheless there are some openings I have tried to circle, that show when I push with my thumb. Too bad I don’t have this curve since that would help for a better contact on the seal.
I guess I wouldn’t know if I have a real problem here until I get the seals from EBay. Not sure if you had a chance to check out the link? This is what I ordered.
https://www.ebay.com/itm/294063092843?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3D674bb0a005d440efb8e19a5e192f0d55%26pid%3D100675%26rk%3D1%26rkt%3D15%26sd%3D294063092843%26itm%3D294063092843%26pmt%3D0%26noa%3D1%26pg%3D2380057%26brand%3DGamo&_trksid=p2380057.c100675.m4236&_trkparms=pageci%3Aa005355d-bb22-11eb-bce4-0e025c475202%7Cparentrq%3A951bc3551790a45ab2779d21fffaf5cc%7Ciid%3A1
Logged
sofia, bulgaria
Artie
Expert
Posts: 1242
yes
Real Name: Richard
Re: CFX rotary breech
«
Reply #13 on:
May 22, 2021, 03:42:50 PM »
I am familiar with the ebay offering but have not personally purchased or used his seals though they look like quality transfer port seals. The large o'ring is fairly common and easy to source, 22mm ID, 25mm OD, 1.5mm cross section with a Duro 70 hardness. The transfer port is not easy to source due to the 3mm thickness and 1.5mm cross section.
While waiting for your new seals to arrive you might try shimming your transfer port seal. It can be done if extra caution is exercised. The cocking lever can be retracted enough to push the rotating breech back after the plastic handle is pried out (don't lose the little metal piece that acts as a tension spring). You need to fashion something that will hold the cocking arm back, that
will not
allow the piston to jump forward and smash your fingers.
Once the rotating breech is rearward enough a dental pick or tiny flat screwdriver can displace the o'ring. You won't likely have a punch and die small enough to make shims but with great attention to detail you can use a piece of dental floss and push in a wrap or two into the groove. Once satified the floss is in place and no extra floss is hanging out of the groove, you can reinstall the 6x9mm o'ring and chrony test the gun.
Otherwise, you can diassemble the gun, shim the small o'ring more safely disassembled, or as noted earlier, place a piece of masking tape over the barrel loading port when disassembled, reinsert the piston and force the piston down the compression tube by hand (with an appropriately sized dowel). If it stops short of going all the way down and is springy and does not drop any further you have good pressure from the piston seal and both o'rings.
You can try the "tissue test" on the breech with the CFX but I never had much luck or trust in it with the rotating breech.
You can test for vacuum with the gun diassembled as well. Because the Gamo piston does not have a latching rod to hold onto while pulling the piston back, you can put a screwdriver into the piston's cocking slot and attempt to force a fully depressed piston back. If vacuum prevents the piston from retracting, you have a good seal.
*
I studied the latest pictures. Is the barrel face and surrounding face flat and flush with the rotating breech face or is it dished out (concave or recessed). If it is now dished from your work I'm afraid you have a problem.
Also, from your earlier post you mentioned finding a "damaged" breech seal after disassembling the gun. Was that
after
the chrony test that indicated a 50 fps velocity drop and were you referring to the large o'ring? If so, the damaged seal could be part or all of the problem.
«
Last Edit: May 22, 2021, 04:23:16 PM by Artie
»
Logged
North Carolina
rumenmalinov
Shooter
Posts: 70
yes
Real Name: rumen
Re: CFX rotary breech
«
Reply #14 on:
May 22, 2021, 07:19:40 PM »
Thanks for the feedback. I will try the dental floss trick.
The surface is just flat and shiny now. When I opened the rifle all was intact except the little breech seal was “shaved” . There were some very sharp edges around the barrel and the velocity started to drop from about 233ms all down to 200’s . Now my problem is after replacing both O ring and the seal the velocity remains around 215 ms nothing close to the 230’s I was getting two weeks ago when I got this brand new rifle.
all that with JSB .547 grams
«
Last Edit: May 22, 2021, 07:34:57 PM by rumenmalinov
»
Logged
sofia, bulgaria
Artie
Expert
Posts: 1242
yes
Real Name: Richard
Re: CFX rotary breech
«
Reply #15 on:
May 22, 2021, 08:16:02 PM »
Ok, hopefully the new seal (s) will get you where you want to be. Good luck and let us know.
Logged
North Carolina
rumenmalinov
Shooter
Posts: 70
yes
Real Name: rumen
Re: CFX rotary breech
«
Reply #16 on:
May 23, 2021, 04:12:08 AM »
Thanks a lot you have been very helpful!
If it’s not too much trouble would it be possible when you have a moment to take few pictures of your CFX with the breach open and closed ? Just to have something to compare at least visually with what I am dealing with here.
Thanks in advance it will be greatly appreciated!
Logged
sofia, bulgaria
Artie
Expert
Posts: 1242
yes
Real Name: Richard
Re: CFX rotary breech
«
Reply #17 on:
May 23, 2021, 10:34:41 AM »
I attempted pictures of the breech but my camera lens is cracked (just found out). Sorry
Logged
North Carolina
rumenmalinov
Shooter
Posts: 70
yes
Real Name: rumen
Re: CFX rotary breech
«
Reply #18 on:
May 23, 2021, 11:06:29 AM »
No prob thanks for trying
Logged
sofia, bulgaria
Print
Pages: [
1
]
Go Up
« previous
next »
GTA
»
All Springer/NP/PCP Air Gun Discussion General
»
European/Asian Air Gun Gates
»
Gamo & Spanish AirGun Gate
(Moderator:
Tpatner412
) »
CFX rotary breech