Post by twodoctors on Feb 12, 2021 10:04:19 GMT
Got my CP88 back from loan 48 hours ago... in fact I have only this pistol for less than 96 hours in total. Shot it once. Naturally it needs to be taken apart for a good look inside.
And by golly, it's not an easy one to open up. There is at least one guide at UBC which I have read once. It did help me with when to expect stuff to start flying out. Here is a link.
www.tapatalk.com/groups/umarexboysclubforum/umarex-cp88-lubrication-t2309.html
And there's also a "crazy" German bloke recording a 1 hour video on disassembly and reassembly of his CP88 after it developed a fault with SA. Watch bits of it. Here is the link.
Here is how I have spend the last 2 hours working on mine.
First thing first. Take the barrel locking nut off. This is located just below the barrel. 2.5mm allen key.
Then remove the compensator. Unlock the slide and take the slide and barrel assembly off.
At this point I realised that I could have just taken the right grip plate off and shove loads of molly down there. Tried it. Made no difference to the trigger pull weight. You don't actually need to take the right grip plate off for the trigger job. If you do, there is a leaf spring that may ping away if you start playing with the mechanism.
In any case the mechanism doesn't work when the slide is forward or off.
Next undo the screws on the right. One on the frame and one on the safety. Undo the two screws on the left side, just under the grip plate.
At this stage you are ready to take the cover off.
In the UBC guide, he talked about the small detent ball on the safety and the slide release lever. You can do the disassembly without touching those, just like the german guy did. However, I think it is a good idea to intentionally take them off in case those parts decide to come loose during other parts.
For the slide release lever, once the slide is off, it can be worked slowly out and will turn 360 degrees. The detent ball is located under the "dot" on the lever. Do it in a bag, or close to a magneic dish to catch it in case it flies off. Same with the safety catch but I'll come back to that in a minute.
Now you are ready to take the cover off and look inside.
On the left side this is what you will see. Notice the CO2 unit is on there, unlike the UBC guide. This is partly because the left side of the safety mechanism (with the small detent ball) is linked to the firing pin. If you had taken the safety off, the CO2 unit can be removed. Note that doing this may cause you to lose the detent ball. Be careful!
This is how "dry" it was inside. There were some oil in parts, but I prefer to smother mine in molly grease.
I took most of the bits off so that I can easily test the trigger (with it closed up).
The hammer release mechanism is controlled by 3 parts. The hammer, the sear and the trigger link bar.
For SA, the hammer is rotated 90 degrees and the sear pushes against the hammer, locking it in position. On trigger pull, the bar (not in view, on the outside of R frame, under the grip) is dislodge the sear and drops the hammer, firing a shot.
The action is unfortunately on the right side of the hammer. All you see in the photo above is obviously the left side, where the hammer spring is attached.
Here is the hammer / sear interface in SA.
And here it is in action.
What I did was to shade in the area that is not part of the sear surface.
I then remove it from the frame and start stoning it.
It's difficult to see in the photo, but I very slightly reduce the surface area of the sear hammer interface. I also rounded off the edge and create a slight slope on the top, to allow the sear to disengage a bit easier. All measured in microns, not millimetres. I took a bit off, put the basic mechanism in, test the trigger, then do a bit more.
Final result was SA from 6lb to 4lb. I can probably do more but I was happy with that result. It definitely felt much better.
So time to put it back together.
This was a bit of a struggle for me, so hopefully my tips will help.
There are a few critical bits you have to sort first before the two halves will meet.
CO2 unit. If you have taken it off the left frame, put it back there. This has to line up with the safety mechanism for it to go back properly.
Left safety. If this was taken off, put it back, including the detent ball. Be careful not to lose it in the reassembly process. Before you put it all back the left side should look like this. Notice how all the notches lined up between the safety and the firing pin.
On the right.
If your trigger shoe came off, this is how it goes back together.
Otherwise this is how it should look.
As you close it, the things that may trip you up are the CO2 unit (very snug fit on both side) and the pins on the safety mechanism. With the CO2, you just have jiggle things a bit. With the safety, it's a bit more tricky.
You should be able to close it, but notice the pin on the right side...
And the hole on the safety mechanism.
These have to be linked together. Very difficult to line that up on top of everything else.
What I did was I close it together and use a small screwdriver to move that ring in place, then slam everything close. It might be a bit easier to close it with the hammer cocked, as the hammer might put too much pressure on the firing pin/safety, making it difficult to close.
Should look like this when done.
Nearly there!
Depress the lever a the front so that you can put the slide release lever back in. The hole should now be unobstructed.
Put the lever back in, then carefully replace the detent ball without losing it! (I dropped it 3 times...)
Put the slide back in, lock the barrel with the screw, and you are back to normal again!
I chucked loads of molly inside and on all moving parts (including the trigger link bar on the outside).
Final result?
Double action
From 7lb to 6lb
Single action
From 6lb to just under 4lb
I'm very pleased with that result.
The sear can be bought from Chambers (SR206) at £6.75 +P&P. Also available from another airgun spare shop online, but almost double the price +P&P.
So DA can be done also. I just haven't got the back up parts to do the work.
As you pull the trigger, the trigger bar pulls on the hammer, rotating it.
And here is the action part on the hammer
And internally
I actually forgot to take a photo of the bar removed. In any case, what I would have done is to round off the surface of that contact point. I would only do it on the bar, as the hammer, being two halves, would be a bugger to work on.
Maybe for part 2 (unless someone else wants to take this on...).
And by golly, it's not an easy one to open up. There is at least one guide at UBC which I have read once. It did help me with when to expect stuff to start flying out. Here is a link.
www.tapatalk.com/groups/umarexboysclubforum/umarex-cp88-lubrication-t2309.html
And there's also a "crazy" German bloke recording a 1 hour video on disassembly and reassembly of his CP88 after it developed a fault with SA. Watch bits of it. Here is the link.
Here is how I have spend the last 2 hours working on mine.
First thing first. Take the barrel locking nut off. This is located just below the barrel. 2.5mm allen key.
Then remove the compensator. Unlock the slide and take the slide and barrel assembly off.
At this point I realised that I could have just taken the right grip plate off and shove loads of molly down there. Tried it. Made no difference to the trigger pull weight. You don't actually need to take the right grip plate off for the trigger job. If you do, there is a leaf spring that may ping away if you start playing with the mechanism.
In any case the mechanism doesn't work when the slide is forward or off.
Next undo the screws on the right. One on the frame and one on the safety. Undo the two screws on the left side, just under the grip plate.
At this stage you are ready to take the cover off.
In the UBC guide, he talked about the small detent ball on the safety and the slide release lever. You can do the disassembly without touching those, just like the german guy did. However, I think it is a good idea to intentionally take them off in case those parts decide to come loose during other parts.
For the slide release lever, once the slide is off, it can be worked slowly out and will turn 360 degrees. The detent ball is located under the "dot" on the lever. Do it in a bag, or close to a magneic dish to catch it in case it flies off. Same with the safety catch but I'll come back to that in a minute.
Now you are ready to take the cover off and look inside.
On the left side this is what you will see. Notice the CO2 unit is on there, unlike the UBC guide. This is partly because the left side of the safety mechanism (with the small detent ball) is linked to the firing pin. If you had taken the safety off, the CO2 unit can be removed. Note that doing this may cause you to lose the detent ball. Be careful!
This is how "dry" it was inside. There were some oil in parts, but I prefer to smother mine in molly grease.
I took most of the bits off so that I can easily test the trigger (with it closed up).
The hammer release mechanism is controlled by 3 parts. The hammer, the sear and the trigger link bar.
For SA, the hammer is rotated 90 degrees and the sear pushes against the hammer, locking it in position. On trigger pull, the bar (not in view, on the outside of R frame, under the grip) is dislodge the sear and drops the hammer, firing a shot.
The action is unfortunately on the right side of the hammer. All you see in the photo above is obviously the left side, where the hammer spring is attached.
Here is the hammer / sear interface in SA.
And here it is in action.
What I did was to shade in the area that is not part of the sear surface.
I then remove it from the frame and start stoning it.
It's difficult to see in the photo, but I very slightly reduce the surface area of the sear hammer interface. I also rounded off the edge and create a slight slope on the top, to allow the sear to disengage a bit easier. All measured in microns, not millimetres. I took a bit off, put the basic mechanism in, test the trigger, then do a bit more.
Final result was SA from 6lb to 4lb. I can probably do more but I was happy with that result. It definitely felt much better.
So time to put it back together.
This was a bit of a struggle for me, so hopefully my tips will help.
There are a few critical bits you have to sort first before the two halves will meet.
CO2 unit. If you have taken it off the left frame, put it back there. This has to line up with the safety mechanism for it to go back properly.
Left safety. If this was taken off, put it back, including the detent ball. Be careful not to lose it in the reassembly process. Before you put it all back the left side should look like this. Notice how all the notches lined up between the safety and the firing pin.
On the right.
If your trigger shoe came off, this is how it goes back together.
Otherwise this is how it should look.
As you close it, the things that may trip you up are the CO2 unit (very snug fit on both side) and the pins on the safety mechanism. With the CO2, you just have jiggle things a bit. With the safety, it's a bit more tricky.
You should be able to close it, but notice the pin on the right side...
And the hole on the safety mechanism.
These have to be linked together. Very difficult to line that up on top of everything else.
What I did was I close it together and use a small screwdriver to move that ring in place, then slam everything close. It might be a bit easier to close it with the hammer cocked, as the hammer might put too much pressure on the firing pin/safety, making it difficult to close.
Should look like this when done.
Nearly there!
Depress the lever a the front so that you can put the slide release lever back in. The hole should now be unobstructed.
Put the lever back in, then carefully replace the detent ball without losing it! (I dropped it 3 times...)
Put the slide back in, lock the barrel with the screw, and you are back to normal again!
I chucked loads of molly inside and on all moving parts (including the trigger link bar on the outside).
Final result?
Double action
From 7lb to 6lb
Single action
From 6lb to just under 4lb
I'm very pleased with that result.
The sear can be bought from Chambers (SR206) at £6.75 +P&P. Also available from another airgun spare shop online, but almost double the price +P&P.
So DA can be done also. I just haven't got the back up parts to do the work.
As you pull the trigger, the trigger bar pulls on the hammer, rotating it.
And here is the action part on the hammer
And internally
I actually forgot to take a photo of the bar removed. In any case, what I would have done is to round off the surface of that contact point. I would only do it on the bar, as the hammer, being two halves, would be a bugger to work on.
Maybe for part 2 (unless someone else wants to take this on...).
