This is really more feedback than a question, but since it's directed at CZ gunsmiths & reps, I thought it might fit in best here. I also figured it best to post on the forum instead of sending an email, as this will allow for more open discussion and for any others with similar experiences to come forward.
The problem:
Aftermarket Mec-Gar 17-round and 19-round magazines will contact the Omega trigger bar spring when fully inserted. If seated with a good amount of force, the magazine can cause the trigger bar spring to dislodge from the frame and become a loose part, rendering the pistol useless. The factory mags that shipped with my 75B Omega do not contact the spring, but come extremely close, so this could possibly also be an issue with any slightly-out-of-spec factory magazines.
My solution:
Create a relief in the aftermarket magazines to eliminate contact with the spring.
Proposed "better" solution:
Extend the length of the trigger bar spring which sits in the frame. I would say that doubling the length of that leg and appropriately deepening the hole in the frame would likely prevent the spring from being pushed out of place in any situation.
Background/detail:
I have been shooting CZs off and on for about five years now - since my father bought a CZ75B when I was in college. Recently, I purchased one of the new CZ75Bs with the Omega trigger system. I have been very pleased with the pistol; I could not find any significant fault with it until I discovered the aforementioned issue when practicing reload drills this evening. While performing these drills, I noticed that the mags were starting to fail to drop free - not just one, but nearly all of them were sticking, requiring manual removal. After checking all of the mags again, they started to drop free again, but the trigger just stopped working - it clearly wasn't engaging the sear at all. I detail stripped the pistol to find that the trigger bar spring was missing. Upon returning to the spot where I was practicing my reloading drills, I discovered the spring on the floor.
After much investigation, I finally found that the problem lie with the profile of the aftermarket Mec-Gar mags I was using. The taper on these mags (from double-to-single-stack) begins slightly higher on the body than the factory magazines. This, in turn, causes the mag to contact the trigger bar spring. If the magazine is seated very glenty, no adverse effects could be seen. However, if the magazine was seated forcefully - as would be done in any practical shooting sport or in a defensive shooting course - it would often cause the short leg of the spring seated in the frame to be pushed up just out of its housing, causing the entire trigger bar spring to become loose betwen the frame and magazine. If the magazine was removed, the spring would generally fall out with it.
By removing everything from the frame except for the magazine catch assembly and the trigger bar spring, I was able to see the actual contact of the Mec-Gar magazine against the spring. I also noted that while the factory magazine does not contact the spring, the clearance between the magazine and the bottom edge of the spring is very, very small. A slightly out-of-spec magazine with a marginally larger width at this specific point would cause the same behavior as the Mec-Gar magazines, while still functioning normally with the pistol in every other sense. Additionally, I am curious about the factory SP-01 magazines; as I do not have any myself, I cannot perform any comparisons or tests. However, if their profile is similar to the Mec-Gar profile, with the higher/wider taper - something I would not be surprised about, given their higher capacity over standard CZ75 magazines - then they would also cause this issue.
Having finally determined the cause of the problem, I decided to go about fixing it. While my first thought was that the spring should be better retained by the frame to prevent this altogether, alas, I have no way to produce a new spring with a longer leg, nor do I currently have a small enough drill bit suitable for deepening the hole in the hardened steel frame. So I decided to modify the aftermarket mags instead. I selected one of the 17 round magazines and created a small relief, using both my dremel and some needle files. This mag no longer contacts the trigger bar spring - and neither I have been able to dislodge the spring by seating this mag forcefully, despite many repeated attempts at doing just that (like I had been able to do before creating the relief).
I am rather surprised that I am the first to report this issue (AFAIK), as Mec-Gar is a particularly popular and well-thought-of aftermarket magazine manufacturer, especially for CZs. I doubt I will be the last to experience this, however, as the short "frame leg" of the trigger bar spring in the Omega system seems to be an inhernet design flaw - albeit one that could easily have been overlooked during actual development, due to the somewhat obscure way (at least from a design point) in which this came into play.
