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Small seal that is on the port: 1 mm x 6 mm
Notice: Front rotary breech seal Update 5/1/2006
I replaced a front (port) rotary breech seal in a late CFX and there is
a different seal in this one. The ID is the same but the seal width was
different.
The larger seal that is used on the later ports: ID= 6 mm
OD= 9.1 mm
(across) Width= 3 mm
The large o-ring around the rotary body: 1 mm x 20 mm
The Durometer of the o-rings should be 70, especially the large o-ring.
The harder it is the less forgiving it will be on the large o-ring and
easier to cut during installation. A Durometer of 70 will be fine. 90
Durometer on the front will work but isn’t necessary and will make it
harder to rotate as will the rear one if 90 Durometer.
Now before we go any further, let me say this. I’ve yet to see one that
has actually been worn out but have seen a number of them damaged.
Unless the seal was actually damaged during the factory installation, it
is doubtful that anything will be wrong with it. However, the seal can
be damaged during shooting. The damage is usually caused by one of three
reasons.
The first major cause is that a lubricant was used that caused the seal
to go soft (or rot). This is usually caused by detergents in oils and/or
other additives. It’s best to use light film of silicone grease if
possible. If any oil is going to be used at all, that it be silicone oil
or at least a non-detergent oil of very light weight and applied very
very sparingly. Some will almost certainly get into the port which of
course we don’t want to happen. The best way to lube it is to slide the
rotary back and apply silicone to the seal and face. See the replacement
instructions below.
The second major cause is that quite often, small particles on the skirt
on the pellet can be sheared off of the pellet as the breech is rotated
into the closed position. There may also be loose contaminates on the
pellet. These particles can be transferred to and in between the rotary
and the block, eventually reaching the seal. If and when it does, it
will score/damage and cut the seal surfaces causing it to leak and lower
the velocity.
A third cause is getting very fine grit and sand into that area. Keep it
clean and as dirt free as possible.
For those that are somewhat mechanically gifted, a bit of a maintenance
suggestion. You may want to clean the rotary housing area between the
rotary block and barrel block during maintenance. Using the instructions
for the front seal replacement below, clean the area with a Q-Tip with
perhaps some GooGone applied to it. Dry it thoroughly. Then lube the
seal and seal contact area very sparingly.
OK…so let’s fix it.
The rotary breech will be referred to as the rotary from here on.
The front o-ring can be installed without disassembly.
Being very careful, cock gun and be sure to put the safety on safe.
Gently work rotary a little to the rear enough to expose breech face and
seal. In the event that you push the rotating breech too far to the rear
to reach the seal you will need to remove stock to access the trigger
area. Remove the small spring located behind the cocking safety link and
the e-clip on the trigger housing holding the link in place. After
disconnecting the bear trap and use cocking lever to carefully uncock
the gun by pulling the cocking handle back a little and then with the
trigger pulled, hold the lever securely and gently let the cocking lever
slide home while pushing the breech forward. You may want to consider
reinstalling the stock when de-cocking. It’s much safer.
Alternative
Here is the best, easiest and safest way. (added 8/9/05)
Take a piece of dowel (I made a permanent fitted one of Delrin as a
tool) ¾ inch diameter and about 5/8 inch long. Drill a 3/8 inch hole
down through the center length wise (gives a little more working area).
Cut the dowel in half lengthwise. This will be your cocking block to
hold the breech back while you remove and install the new seal. You may
want to trim it as you see fit.
Remove/lift the rotating lever on breech straight out. Watch for the
little flat spring on the lever. Grasp the cocking handle a pull the
cocking lever back a short distance (do not cock the gun) and while
holding it back, slide the rotary back just far enough to set your
breech block in place. Position the block it so access to the seal is
possible and the block will not interfere with the seal removal. Now
slowly release the handle and let the spring push the rotary up against
the block. You can now safely remove the seal. Lube the seal and face
area with 100% Silicone grease or a good alternative.
To replace the rear seal is more difficult and requires disassembling
the gun and the seal installation is critical as it can be damaged very
easily and unknowingly. Also, consider “tuning” the gun as you already
have it apart and deburring is a big part of the tuning process. I’m
sure that when the gun is assembled at the factory, the breech is
installed from the front during the assembly process. However, if I need
to replace them, I’m in the tuning process anyhow so here is procedure I
use.
Disassemble the gun and with the piston removed, lift the lever on
breech straight out. Again, watch for the little flat spring on the
lever. Take notice of the position of the rotary so when reinstalled it
will be close to the right position. Push the rotary out the rear of the
tube. You are guaranteed to damage the seal (if not already damaged)
when you push it out as it will be cut while extracting it by the sharp
edges on the inside of the tube. Now comes the most important part.
Everything needs to be deburred the whole length of the tube from the
rear at the trigger area including the cross pin holes down through the
cocking slot. All sharp edges have to be eliminated. This is critical.
If not, when you install the rotary with the new o-ring, you will almost
certainly cut the new o-ring (remember, it’s only 1mm thick) and
probably not even know it. Clean the tube and wash out thoroughly.
Clean the rotary paying special attention to the o-ring grove. Now
install the large o-ring on the rotary and apply a thin coating of 100%
dielectric silicone grease around the rotary and outer surface of the
o-ring.
Note….do not lube the ring groove or o-ring before installing the
o-ring.
The reason here is that you want to prevent it from rolling if possible
while inserting it into the tube. Apply the silicone (very light film)
on the surface of the o-ring and rotary after the o-ring is installed on
the rotary. Also, apply a coating on the front surface of the rotary and
on the face of the breech while trying not to get any or as little as
possible in the ports. You can now also install the front o-ring but if
the small one is used, it may want to fall off. If so, just install it
after the rotary is installed and just before the rotary reaches home.
Now, ever so carefully, reinstall the rotary being careful not to damage
it during the installation and that it’s in the approximate correct
position. It is very easy for the o-ring to “roll over” the edge of the
grove as it passes over the stamped out edges and get cut so be very
careful and observe it closely during installation. With the front seal
in place, re-install the spring and lever into the lever. Now finish
“tuning” the gun and reassemble.
CharlieDaTuna
Revised 8/9/2005
Revised 5/1/2006 |
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