455 feeding problem
Posted 10 December 2012 - 01:39 PM
I previously had a 452 that I tweaked in the usual ways and put into a target stock that I finished myself. It could put bullets into the same hole time after time at 50 yds. Recently it was stolen from my home and when I went to replace it saw the 455 Evolution which I found to be very attractive. So I got one. I'm thinking now it may have been smarter to get another 452 and restock it, but I have what I have and will stick with it.
When I pulled the barreled action out of the stock I saw that some real compromises had been made in order to support the multiple barrels and cartridges. Where the 452 had a very nice and solid front stock bolt there was this huge expanse of open space between the front of the action and the rear of the action!! And the stock bolts just went through a lot of air from the bottom of the stock to the action. Oh well. I pillared and epoxy-bedded the action (before even shooting it), and today set up a quasi bench rest on my back deck to check it out informally at 50 yds. (with a 24 power scope). The rifle appears to be highly accurate (a la the 452), but needs some breaking in. The bolt is VERY stiff. I may decide to lap it. We'll see about that. I like the stock (which I know some find to be a bit goofy).
The big shock/surprise was the difficulty (roughness) in chambering cartridges. If I was really careful to hold the bolt handle all the way up against the receiver, it worked pretty well. But otherwise it would frequently hang against something as the bolt was being run forward. Worse, when pushed with a bit more force, the cartridge would partially stovepipe and then partly crumble (yeah, an actual bend/dent in the case!). This is very disconcerting. It's possible that this was contributed to by partly backing up the bolt and trying again, but it happened a bunch of times.
So I wonder if anyone else has had this happen and what the recommendation is for addressing it. My guess is that this is a consequence of another compromise that was made for the multiple caliber system. It looks to me as though the bolt and the bolt guide are not playing well together. I'm pretty sure I have them reassembled correctly. The magazine isn't loose. The bolt guide isn't loose. But feeding is far from reliable at this point. I don't recall the 452 having a separate bolt guide. Yet another part to get loose or out of alignment or worn in an odd way, or so it seems to me.
Does anyone have similar experience? Any suggestions?
-- Gary Merrill
Posted 10 December 2012 - 01:45 PM
Posted 10 December 2012 - 01:55 PM
Posted 10 December 2012 - 02:53 PM
I haven't noticed any issues like that with my 455, bolt is a little stiff compared to some of my other guns but I haven't shot it as much as the others. There is a post in here about lapping your bolts, might try that but would also consider perhaps the bedding is binding it somewhere.
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Posted 10 December 2012 - 04:15 PM
The Canuck: The receiver is heat treated after machining and warps and bulges slightly
As he explained to me after having to lap the tenon on an aftermarket barrel to obtain a fit.
You can see the ridges created by the heat treatment that had to be worked down with lapping compound.
I'd be looking at the magazine fit as the cause of the stovepipes.
Sounds like it's not fully seated or misaligned. When you pillared did you check
that no threads pushed into the receiver when tightening the action screws?
I had to check pillar fit multiple times to ensure that the screws stayed below
the level of the floor of the receiver. Otherwise the screws interfered with the bolt.
Is the bolt guide in full contact with the floor of the receiver?
Edited by jaia, 10 December 2012 - 04:17 PM.
Posted 10 December 2012 - 06:26 PM
I'm aware of the problems with magazine alignment and seating in this model, and I don't think that's the problem, but I do need to do more testing. I do have multiple magazines and will try all of those.
Likewise, I know the problem isn't the pillars or the bedding. This is not (by far) the first time I've epoxy- or glass-bedded an action, and this one was pretty straightforward. The only real problem with the pillars is that you need to cut a notch (or ramp, though a notch is easier and no less effective) in the top rear of the front pillar to clear the front of the magazine bracket and its screw. I regard this as a design defect in this rifle since it means that you can't truly pillar the front action bolt. There just isn't room. You end up with kind of a "half pillar". Another compromise, clearly, mostly for the .22 WMR. But it's a .22. So we're not concerned about recoil here -- just getting a solid and repeatable seating and torque-ing of the action into the stock that won't be affected by temperature and humidity.
I've played with it a bit more and am fairly convinced at this point that it's just a matter of wearing in. I'll look into lapping (which twenty years ago I would have jumped at), but I have become inclined to avoid lapping anything unless really necessary. Better too tight for a while than too loose forever.
Additional lubrication helped -- suggesting that some judicious stoning in just the right places might help. But again, I think I'll be ultra-conservative here. The only oil I put on it was Alisyn (which is a low viscosity synthetic oil used for brass musical instrument valves). This was primarily because I knew that some wearing in would be needed, and light oil is better for that..
This gun's action does definitely seem tighter than I remember the 452's being (when I got it new). But that should actually be a good thing. However, even before I began any of my work, closing the bolt was an effort. Nothing wrong there, I'm sure, but it immediately reminded me of a "cock on close" Mauser. It just locks up quite tight. Again, a good thing if not overdone. And it does seem to be getting a bit looser. My sense (without measuring anything of course) is that tolerances on the 455 may be closer than on the 452 (a somewhat odd contrast to "openness" of the stock where the action fits .
What I was looking for in the forum was someone who might say "Oh, yeah, there's a well known issue with that; and here's the story ..." But I'm not hearing that, and so I think there's nothing particularly wrong. I'll just recheck everything according to your recommendation so I haven't overlooked anything, and then see how it wears in over a few hundred rounds.
This afternoon, the trigger kit arrived (geez the trigger really sucks on these rifles, but that was pretty much true on the 452 as well), and so maybe tomorrow I can get the trigger to behave well.
Thanks for the attention to this and the suggestions.
Posted 10 December 2012 - 09:41 PM
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Posted 10 December 2012 - 09:46 PM
Posted 10 December 2012 - 09:46 PM
Posted 10 December 2012 - 09:52 PM
Posted 11 December 2012 - 07:50 AM
i'm almost 100% sure thats what it is it could be that them parts didn't get milled out very well. good luck if want to just go and get a new shell holder and shell Extractor cz will replace them for free if you mail in the old parts.
Thanks. I had seen that mentioned in some other forums/threads but had forgotten about. Will definitely check it out.
Posted 22 January 2013 - 08:05 PM
― Aldo Leopold, A Sand County Almanac
Re shooting: "40 years ago, I was MUCH better at this"
Posted 22 January 2013 - 08:14 PM
The trigger kit makes a huge difference. It's an accurate rifle.
Posted 23 January 2013 - 10:56 AM
The extractor claw is typically longer and extends deeper into the woodruff slots cut on the breach for it. Take some white out (liquid paper) and lightly coat the areas circled in green and then cycle the action to see if they are scraping. You can nip these areas down with a stone if needed.
I would highly advise against stoning the lug area of the receiver or the bolt handle to get things to free up. this will permanently increase your headspace on battery, A more likely cause of holding up the bolt from battery are the prong like tips of the bolt guide that extend up the face of the breach. If the headspace is set too close, the upper part of this can come in contact with the recess milled into the bottom of the bolt nose. I see this quite commonlu occur when I reduce headspace down to .043" from the factory stock .046-.048" setting.
You can check if its the bolt guide prongs interfering by removing the bolt guide and cycling the bolt (no round in it). Another way to check is to cut several ring washers out of paper and place between the barrel lip and the receiver when you assemble the barrel. This pushes the barrel back ~ .003" for each peice of paper washer thereby incresing headspace and clearance on the bolt guide tip. Sometimes the bolt guide face will remain in the same position and a gap will appear between it and the breach face so this latter method does not always work. This is because the bolt guide is positioned by the rear mag screw. If this is the case, do what follows here...
Marking the the bolt guide tip or the bottom of the bolt nose with dykem blue or black marker will often show if they are interfering also. Sometimes just a tiny chamfer stoned on the bottom of the bolt nose is all it takes...other times I will grind/chamfer the face of the bolt guide a bit to thin it out for more clearance. If your unsure of what I'm talking about here, let me know and I can dig up a few photos I have that would clarify it.
Edited by The Canuck, 23 January 2013 - 11:01 AM.
Posted 23 January 2013 - 12:03 PM
I was planning on doing something with the extractor along the lines you indicate, but was unsure of where exactly this should be done. The white out is an excellent hint to determine if there is any problem in this area.
I'll also pull the extractor out and see what difference that makes. I hadn't thought of that at all.
I'm not sure what you mean by "bottom of the nose", but I suppose this means the part at the bottom of the face directly below the firing pin hole and extractor. There is a narrow lug (about 1/8" wide and 1.75" long) running from the bolt face back along the bolt bottom, and I mildly stoned this, which exposed some tool marks (these appear to be either from a milling bit or perhaps some polishing tool). This portion of the bolt bottom appears then to be a bit crudely finished.
Absent a Dykem marker, I have resorted to blackening this lug and the bottom of the bolt face with a Sharpie, and cycling the action a number of times. There are no points where it appears to rub. The bottom of the bolt face already appears to have slight champfer on it as well.
The force required to close the bolt on an empty chamber seems (subjectively, but still rather distinctly) to be a bit less than that required to close the bolt on a round. This is what was pointing me in the direction of the extractor.
As a matter of curiosity, is there a reasonably straightforward way to measure headspace on this?
Posted 23 January 2013 - 04:56 PM
Plastigage can be obtained from most auto parts depots and is not very expensive.
Some gunsmiths used to use a sliver of very soft lead on the back of a casing or gage.
Rim thicknesses do vary a touch between brands and even on the same ammo to some degree.
The CZ bolt uses a two stage process to cock. When the bolt is opened, the striker is cocked back 1/8" and held in place by the cam on the bolt handle ring/collar. After ejecting the spent round when the bolt is closed, the remaining 1/8" is cocked via the curved cam near the back of the receiver. You should feel resistance from the striker spring compressing as the bolt handle goes down for this 2nd part of the cocking...that is normal.
Posted 23 January 2013 - 06:12 PM
Is that 2-stage approach new to the 455? I don't remember feeling anything like that with the 452. Could easily close it with just thumb while keeping the rest of my hand on the grip, as I recall.
Posted 23 January 2013 - 06:19 PM
Watch the two rear wings of the striker at the back of the bolt. It moves back 1/8" when the bolt is lifted and then another 1/8" when its closed. The bolt does need to be cycled back in order for the sear pawl to catch the bottom of the striker I believe. With the bolt out of the gun, you can fully uncock it by rotating the handle.
Edited by The Canuck, 23 January 2013 - 06:23 PM.
Posted 23 January 2013 - 06:49 PM
Posted 28 January 2013 - 05:45 PM
When I checked the bolt action in slow motion, I noted that tips of bullets were hanging on the breech face off the ramp and not entering the bore. Was happening with both barrels, and both metal and plastic tipped on my .17HMR rounds.
I did examine the breech of my 22LR and 17HMR barrels and noted a slight burr around the breech mouth on the face that would easily catch a fingernail. I lapped the face right around the bore and knocked down the burr. Bullets are sliding smoothly up the ramp, over face and into the bore now. The Cartridge rims are seating great, There is no obvious deformation of the shells and they extract well. I dont think I rounded the bore/face edge significantly and it seem to have worked well with no impact on accuracy, discharge and extraction.
I did this on gut without too much concern since the material I lapped away was magnitudes less than the tolerance around the shell in the bore and I was not changing the shape significantly.
Posted 31 January 2013 - 10:15 PM
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― Aldo Leopold, A Sand County Almanac
Re shooting: "40 years ago, I was MUCH better at this"
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