Yes, another of these threads.
Yes, I have read the others. I guess I'd just like some impressions from others who may have encountered this in order to determine what my realistic expectations should be and whether I should pursue doing something to "improve" things -- either by myself or via CZ.
Background: I had a CZ 452 and loved it. Alas, in a fit of irrationality, I replaced it with a 455. The 455 is, in itself, great. It's superbly accurate. I love shooting it. But it had this "issue" from day 1, I've improved it about as much as I can with simple methods, and it still seems a bit odd to me.
The action is very smooth -- I mean REALLY smooth. No problems there. I've put several thousands of rounds through it. Everything works. When I close it on an empty chamber, there is some resistance, but that's to be expected as the bolt handle cams against the action surface. I can close it with just thumb pressure on the (stock) bolt knob, but not exactly "butter smooth" or totally effortless. Opening the cocked bolt is pretty easily done with just the index finger.
Closing the action on a chambered round isn't really much different. But as the action heats up, there does seem to be an increase in the effort needed to lift the bold handle and cock the bolt, and to close the bolt to chamber the round. But I can't quantify this.
Looking at this, it's hard to see what I'm complaining about. But I remember the 452 action being virtually effortless to work fast with index finger and thumb -- like "Olympic speed". The 455 isn't there.
What I've done:
- Checked to be sure eveyrthing seems good with the chamber, the extractors, the bolt itself, etc. No obvious problem.
- Very carefully polished various bearing surfaces of the bolt itself and the cocking mechanism.
- Carefully filed/stoned the surface on the rear of the receiver notch that the bolt handle cams against to close and seat the cartridge. This has definitely improved things, but not entirely. I actually bought a new "backup" bolt in case I screwed this up. When I switch bolts, I don't see any difference in how the bolt is seating, I see no signs of excessive headspace, but the running the action with the "new" bolt is clearly stiffer than with the old one. I've had the experience with the new bolt that when the gun heated up, the action became almost impossible to work. Although visually identical (except for the hole in the new bolt knob, its matte finish, and an odd deep rectangular "cutout" in the underside of the bolt handle), there do seem to be some minor dimensional differences on the order of fractions of a mm.
I don't believe I've replaced the original striker spring. I have no record or memory of that, and there's no spring in my parts boxes that looks like a striker spring for a CZ 45x.
So at this point I'm pretty sure I haven't screwed up anything (particularly headspace), and have achieved some improvement to where I feel the functioning is "okay" to "good". I'm wondering if I should attempt to go further in terms of filing/stoning the bearing surface of the bolt handle or quit while I'm ahead. I'm wondering if this is just the nature of the beast and the 452 just had a slicker action (possibly because of changes for the 455 made to support multiple calibers). I guess that if I'd never had the 452, this situation with the 455 wouldn't be bothering me at all.
Comments, suggestions, advice, ridicule ...? At this point I'm just mostly curious and looking for peace of mind. 😂