I did some investigating into the problem D Hunter reported, regarding his CZ 550 sometimes failing to cock. I examined one of my own CZs and found I could recreate this problem. Here are two pictures illustrating the problem, along with an explanation. First, the way it should be:



This photo illustrates the way the sear should return to position after lifting the bolt handle. It springs all the way back up and clears the trigger. Now here's the problem:



This shows the sear hung up on the rear of the trigger and therefore not resetting to its proper position. Compare the area in the red circle to the picture above.

Note that in both pictures the bolt is open and partially retracted. As soon as the cocking piece clears the sear, the sear SHOULD spring back up into place (reset). The malfunction occurs when the sear gets stuck on the back of the trigger and doesn't reset. When this happens, the sear isn't in place to catch the cocking piece as the bolt closes. The result is an uncocked rifle with the firing pin resting on the primer of the chambered round. Not good.

D Hunter reported that this happened more often if he short stroked the bolt of his rifle. On my rifle, I found the problem only occurs if the bolt is lifted very gently and smoothly. To me, this indicates that the jolt of opening the bolt briskly or bringing it back against the bolt stop smartly is enough to jar the sear loose so that it resets properly.

How do we fix it? My guess is that two things need to be done. First, a stronger sear spring will help to assure that the sear resets properly. Second, the back of the trigger and front of the sear should probably be polished a bit more to reduce friction and decrease the chances of these surfaces sticking.

I don't know the history of D Hunter's rifle, but mine is completely unaltered and exactly as it came from CZ. No attempt has been made to adjust the trigger or otherwise change any part of the rifle.

I'll be contacting CZ-USA regarding this problem ASAP and reporting back to the group regarding their response. In the meantime, if any forum members could check their guns for this problem and report back, it would help establish how widespread this condition might be. Phil Shoemaker reported having the same problem with his CZ in "Rifle's Hunting Annual" number 6, fall 2002.

Thank you.

Best,
Joe

[ 07-14-2003, 07:30: Message edited by: nextjoe ]

I spoke to Mr. Mike Eagleshield, gunsmith at CZ-USA, this afternoon regarding the problem I found. He told me he has seen this problem before, but not frequently. He recommended adjusting the overtravel screw to allow more overtravel, lightening the tension on the trigger return spring, and lightly stoning the front face of the sear. He also said that there are no stronger sear springs available. I'm going to take his advice and try the changes he suggested. If that doesn't correct the problem, the gun will be going back to CZ-USA for repair.

I'll keep the forum informed of my experiences.

Best,
Joe

Tonight I tried fixing my CZ according to the directions given to me by Mike Eagleshield at CZ-USA. I lightly stoned the front face of the sear, where it bears against the back of the trigger when in the "fired" position. I worked slowly and carefully to avoid rounding the corner of the sear, and I didn't stone very much. I checked the overtravel, which is more than sufficient. I did not adjust the trigger return spring tension, since I couldn't find the right size wrench in my toolbox and I didn't want to chew up the lock nut with a pair of pliers.

Result? The problem is still there. The sear resets if the bolt is opened briskly, but occasionally sticks if the bolt is opened slowly and smoothly.

One thing I noticed is that the rear of the top of the trigger, which bears against the front of the sear, is very rough. This part is pinned and staked in to the trigger housing, so I couldn't remove it to polish it. I also wasn't about to go tearing around in there with a Dremel

My conclusion is that there is excess friction between the rear of the trigger and front of the sear. If the surface finishes were smoother, and/or if the sear spring were stronger, the sear would reset properly under its own power. As it is, the sear sometimes sticks on the trigger and needs a small jolt to bump it free.

I'll be getting back in touch with CZ-USA and having them issue a return authorization so Mike can examine and repair it. I'll keep the forum posted.....

Best,
Joe

[ 07-16-2003, 05:48: Message edited by: nextjoe ]