Gamo Urban bolt probe o-ring chewed up.

[Vee3]

Upon tear-down to install a CDT trigger in my Urban, I noticed that the bolt probe o-ring had material sliced off of it. 

Suspecting that the magazine was the cause, I took it apart (slivers of o-ring were inside) and found that the hole in the steel plate where the bolt goes through had a very sharp edge on the inside. I used a Cratex point in my Dremel to remove it, and formed a slight radius on both inner and outer edges of the hole. Under magnification, I could see that there were also small edges in the hole in the plastic housing, as well as in the "cylinder" (to borrow a term from revolvers). I carefully removed them with an X-acto knife.

Problem I see here is with the magazine's spring applying lateral pressure to the bolt probe as it's sliding through; any sharp edges within the mag
 that contact the o-ring are going to dig into and damage it.

With a new (006) viton o-ring installed, there is no damage to it after cycling (no pellets, but pushing/pulling on the mag slightly as the bolt goes through) ~100 times. I'll monitor to see if it holds up after "live" firing.

Side note - I found that a #20 drill shank is the perfect diameter to make the required pin to install the CDT trigger.

[MaineJim1821]

When i first got my Urban i had a couple of double feeds that i believe were the cause of that o-ring being blown off to bits.
What a pain to put a new one on it was,now after over two thousand pellets the o-ring looks like new still ,my magazine didnt have any sharp edges at all.
Looks like you took care of yours,how do you like the CDT trigger ,i got one on a Titan and its definatelly an improvement.
The trigger on my Urban is under two pounds but its very vague as to when it trips.

[toddbrat]

Did you happen to take any pics while you had it torn apart? Not a huge fan of the CAT trigger, at least the creepiness before it finally breaks.

[Vee3]

When i first got my Urban i had a couple of double feeds that i believe were the cause of that o-ring being blown off to bits.
What a pain to put a new one on it was,now after over two thousand pellets the o-ring looks like new still ,my magazine didnt have any sharp edges at all.
Looks like you took care of yours,how do you like the CDT trigger ,i got one on a Titan and its definatelly an improvement.
The trigger on my Urban is under two pounds but its very vague as to when it trips.

I had the Urban out today, tagging along with my buddy who was deer hunting (didn't see any). I killed a bunch of pine cones and acorns; put about 5 mags through it. O-ring still appears as new.

The OEM trigger wasn't too bad for a hunting gun but a little vague and mushy. CDT is a real improvement and worth what it cost IMO.

[Vee3]

Did you happen to take any pics while you had it torn apart? Not a huge fan of the CAT trigger, at least the creepiness before it finally breaks.

Sorry, I didn't take any pics.

I don't think the CAT is a very good design but I've seen worse. At least the sear and intermediate lever between sear/trigger are through-hardened (not case-hardened) steel, so I was able to remove most of the 2nd stage creep by stoning the edges of the lever/sear interface to sharp corners. It breaks cleanly and predictably now.

[MaineJim1821]

Thanks for reply Victor.