Mauser Action Feeding Work - CZ 550

So good to see such a positive result. There is nothing quite like the satisfaction of worrying through a problem and putting the personal effort into the fix. I am sure your efforts will be a great help to others having a similar problem.
Just another shining example of why this forum is the best there is.
 
I concur, this is a great write-up and explanation. You really did great work , I suggest when completing your PH licence do considering commencing studies to become a gunsmith , you really have the quality and insight into such a trade. I really think you will be great being a gunsmith...few old and knowledgeable gunsmiths has cracked this conundrum as you have done it. Johan Greying is one of the few gunsmiths I know of that knows how to make a Mauser Action/clones there off feed in any circumstances. Making a .500 Jeffery feed in a standard Mauser 98 action is the benchmark of mechanical gunsmith prowess . Thank you for this great write-up, I will definitely study it closely, yes, Von Gruff is another talented mechanical guru who is able to explain a difficult concept in such a way that even a person like me understand the difficult concept as a whole...:A Big Hello::A Big Hello:
 
T
I concur, this is a great write-up and explanation. You really did great work , I suggest when completing your PH licence do considering commencing studies to become a gunsmith , you really have the quality and insight into such a trade. I really think you will be great being a gunsmith...few old and knowledgeable gunsmiths has cracked this conundrum as you have done it. Johan Greying is one of the few gunsmiths I know of that knows how to make a Mauser Action/clones there off feed in any circumstances. Making a .500 Jeffery feed in a standard Mauser 98 action is the benchmark of mechanical gunsmith prowess . Thank you for this great write-up, I will definitely study it closely, yes, Von Gruff is another talented mechanical guru who is able to explain a difficult concept in such a way that even a person like me understand the difficult concept as a whole...:A Big Hello::A Big Hello:
Thanks Gert. I am a teacher by training but have been involved in building mining plants for the last 10 years. My mind just can’t leave a mechanical problem alone until I have the solution. Just built that way. I would love to study gunsmithing but there is little chance in Zim.
 
So good to see such a positive result. There is nothing quite like the satisfaction of worrying through a problem and putting the personal effort into the fix. I am sure your efforts will be a great help to others having a similar problem.
Just another shining example of why this forum is the best there is.
I enjoy this forum too. Loads of information and experience and generally people just want to help. Hopefully my post will be helpful to someone out there.
 
in answer to post 15, yes i think it is crf if the rim is against the boltface and under the extractor.
what do others think?
bruce.
 
GREAT article and very well written, the go to guide should my CZ550 458 Win Mag start with feed problens...so far it is behaving excellently.
Good luck with your Zim PH finals!!!
 
So, I was doing some practice drills and.... had a jam ! Retried,another jam. The bolt handle was a little hard to lift on that round too, on a dummy round. So I had a good look and noticed the bullet was pushed back into the case. Fixed the problem and all was ok. It started me on another investigation though. It seems that shorter OAL has an impact on feeding as well. So I started some investigating the two rounds that I have right now and comparing the actual dimensions. The attached picture give the dimensions. I noticed a few things-Hornady DGS 480 gr solids will give you an OAL 4,5 mm shorter than maximum. This means that a different crimping groove would give them about 10 % more case capacity and still remain within specifications ! With the .458 win mag reputation, you would think they would give themselves all the case capacity they could. The Peregrine 450 gr is seated well out from the case but also has a couple of mm to spare. Anyway, if you have some missfeeds in the CZ 550, try a longer bullet, The Peregrine round has a longer OAL and feeds easier in my rifle. The Hornady DGS will jam if OAL is reduced by 1-1,5 mm in my rifle. So in the CZ 550 in 458 win mag, the longer monometal solids would appear to offer an advantage in feeding reliability, contrary to everything you read and hear simply because they are longer. Also it seems that factory ammo is often shorter OAL than specified and that doesn't seem logical for the win mag either. They limit case capacity by putting the crimping groove quite far forward on the bullet and leave several mm that could be used for powder. I dont really understand it.

fgh.jpg
bgh.jpg
 
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Gee all that makes my head spin great write up, i built a 35 whelen on a FN 30/06 action once could not get to feed well, refitted barrel to ruger mk 2 30/06 it fed with no problems wish i had this information then.
 
Fascinating write up

I’ve had feed probs with my Mauser 98 in 404j since I’ve had it

it has been with a gun smith for the last year

I’m due to get it back next week and if it fails to perform during shooting drills I shall be sending it back with your excellent write up
 
It does pay to do the cycling drills. A long time ago I noticed large differences in the location of crimp grooves on 45 caliber rifle bullets. That location combined with nose length and nose profile determine the critical cartridge OAL and feed geometry of each loaded round in any particular bolt action. No wonder there are variables in cycling reliability.

You can take a slo-mo video (high frame speed setting) with some cell cameras of the actual feed process as the round negotiates the critical area of the feed cycle when the round is pushed over the hump of the feed ramp and into the chamber. That transition from the lower level (plane) of the magazine into the higher level (plane) of the chamber is where most of the trouble is when there is a jam. It is best done with help- it's hard to cycle rifle while holding camera/cell :) Such video may help pin point what is actually happening during the process. In reality, correcting feed issues is sometimes easier said than done though even when you witness the moment of the problem as it happens.

Thanks for posting the heads up, particularly for anyone with a DG rifle. Never hurts checking an action for trouble free operation by cycling the bolt with as many types of bullet/OAL combinations as are available- spire point, round nose, flat nose, full magazine, one round in magazine, variable seating depths and even empty cases.
 
Nhoro - outstanding post - a clearly written description of the problem and the fix.

I have a Dakota rifle that gave me fits and made several trips to the gunsmith before it was 'acceptable', though not perfect by any means. Thanks.
 
It does pay to do the cycling drills. A long time ago I noticed large differences in the location of crimp grooves on 45 caliber rifle bullets. That location combined with nose length and nose profile determine the critical cartridge OAL and feed geometry of each loaded round in any particular bolt action. No wonder there are variables in cycling reliability.

You can take a slo-mo video (high frame speed setting) with some cell cameras of the actual feed process as the round negotiates the critical area of the feed cycle when the round is pushed over the hump of the feed ramp and into the chamber. That transition from the lower level (plane) of the magazine into the higher level (plane) of the chamber is where most of the trouble is when there is a jam. It is best done with help- it's hard to cycle rifle while holding camera/cell :) Such video may help pin point what is actually happening during the process. In reality, correcting feed issues is sometimes easier said than done though even when you witness the moment of the problem as it happens.

Thanks for posting the heads up, particularly for anyone with a DG rifle. Never hurts checking an action for trouble free operation by cycling the bolt with as many types of bullet/OAL combinations as are available- spire point, round nose, flat nose, full magazine, one round in magazine, variable seating depths and even empty cases.
Yes, try them all. But flat point or meplats seem to be the worst. My gun won't cycle with empty cases because I have tuned it for the bullet to enter the middle of the chamber. So the empty hits the side of the chamber. But it cycles a backwards bullet, so calibre sized meplat.
 
Nhoro - outstanding post - a clearly written description of the problem and the fix.

I have a Dakota rifle that gave me fits and made several trips to the gunsmith before it was 'acceptable', though not perfect by any means. Thanks.
Glad you enjoyed my post. I am sure a good Smith can perfect a mauser feed, it is all about the original principles of the design.

Wider magazine= round feeding closer to the rail that it is against
Removing rail= same thing
Thinning or sharpening the rail= same thing
Lowering the ramp= same thing+ bullet enters lower in the chamber
Polishing can hange things so polish after any work
The claw shape and polish effects the feel/ smoothness of the feed but go to far and you lose the tight grip on the cartridge.
 
The great thing about this forum is that people are so willing to share their experience and knowledge. It was the post from Von Gruff that gaveme the background to figure things out
 
The difference between the dynamics of a slick, reliable bolt feed and a jerky, unreliable feed can be very, very subtle. A slo-mo video may help analyzing the culprit. The journey of the cartridge from magazine and on into the chamber is truly a complex, three dimensional process with multiple variables affecting each phase.

One phase of the journey I've noticed in some of my Win M70 actions that can differ some from a normal Mauser feed happens just before and at the moment of full capture by the extractor as the front of the round or the nose of the bullet contacts the ramp. In my newer Win70s, the bullet contacts the ramp and nearly instantly the rim/base of the case moves upward into full engagement of the extractor on the bolt face. On many other Mausers, including CZs and older Winchesters there is a slight delay in that capture as the bullet nose rides up the ramp and the base of the case is still being pushed forward by the lower edge of the bolt and has not seated up into full extractor capture on the bolt face. This can result in a "jerky" feeling or slight resistance felt during the forward bolt thrust. One thing that can smooth this transition is to dress the inside, leading edge of the extractor with a stone while putting a slight bevel there to assist smooth entry of the case rim. The other variable that affects this phase of the feed is the lower edge of the rails and their spacing/geometry in relation to the cartridge stack and cartridge dimensions. As has been mentioned, Mauser figured out that geometry and formula a long time ago and it needs to be re-visited or at least considered each time a cartridge with slightly different dimensions is mated to an action during a conversion.

I took some slo-mo video of two actions showing the point I was trying to make about the difference between the newer M70s and some other CRF bolt actions. I extracted a frame from two slo-mo videos at about the moment the cartridge base should be fully captured by the extractor and the bolt face during the forward thrust of the bolt. Both show cycling of empty cases at about the time in the sequence as the front of the case or bullet is well up the ramp. The first frame shows a 416 Rem in a Win 70 ca 2003. The second frame shows a 458 Watts in an MRC '99 ca 2015. I was feeling that slight jerky hesitance in the MRC during forward bolt thrust. The reliability of feed and cycling was fine but I didn't like that "feel". I smoothed and slightly beveled the inside leading edge of the extractor and voila, nearly eliminated the hesitation during capture.

Win 70 416 Rem feed.png

Screen Shot 2021-07-22 at 12.04.27 PM.png
 
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Fourfive8 that is a good point. I did exactly what you are saying- polished the bolt face and the 2 corner and claw where the case rides up against. Can't remember if I documented that part. I got pictures from another forum that showed the problem. I will take a couple of pics on the weekend. It makes a huge difference to the feel of the bolt. I left mine a little tight because that also sets the tension of the extractor so I erred on the side of caution. My brother has a 416 rigby cz 550 which is smoother at that exact point. I am always tempted to go back and work on that. But I don't notice it much. Polishing those surfaces is vital for smooth feeding. And the corners on the bolt face can cause a jam, the rim gets stuck under it.
 
Fourfive8 that is a good point. I did exactly what you are saying- polished the bolt face and the 2 corner and claw where the case rides up against. Can't remember if I documented that part. I got pictures from another forum that showed the problem. I will take a couple of pics on the weekend. It makes a huge difference to the feel of the bolt. I left mine a little tight because that also sets the tension of the extractor so I erred on the side of caution. My brother has a 416 rigby cz 550 which is smoother at that exact point. I am always tempted to go back and work on that. But I don't notice it much. Polishing those surfaces is vital for smooth feeding. And the corners on the bolt face can cause a jam, the rim gets stuck under it.
Let me add a few tips to this great thread. I built a 404J on 8mm Cech Mauser last year. Lack of gunsmith availability necessitated me doing the work to bottom metal, extractor, feeding rails, loading ramp, and follower (a local machinist opened the bolt face). First, I discovered the magazine box dimensions are not as critical as the Paul Mauser's "cosine 30" formula indicates. I used bottom metal for 416 Rem Mag which was slightly narrower at the back than Maiser's prescription for 404J and even more so at the shoulder area. Nevertheless, it worked fine without modification. In fact, I think the slightly narrower shoulder squeeze actually helped line up fatter 404 cartridges more towards the center of the feeding ramp. Also, it is VERY IMPORTANT to tune the feeding rails in a specific order. Load the magazine fully so that right rail is being reshaped while another cartridge is underneath. Then proceed to tune the left rail with one less cartridge in the box (two cartridges in a 3+1 standard Mauser action). Once both rails have been tuned with three and two cartridges in the magazine, see how the gun cycles loading just one cartridge in the box. Odds are the right rail will now not cycle smoothly or as smoothly as when the box is fully loaded. Don't touch the rails! They are fine. The problem is with the follower. I had to carve a bit of metal from the follower keeper bar a short distance ahead of the back end.
20230909_130729.jpg

This kept the rim in the proper place when bolt face first contacts the last shell in the magazine (i.e. enough rim for bolt to catch on but still enough feeding lip to keep the cartridge in the box). Then as the bolt moves forward the cartridge slips sideways into the carved out section allowing the rim to align properly below the bolt face at the exact point when cartridge is supposed to jump the rails onto bolt face and inside the extractor claw just as the bullet is entering the chamber. That way the cartridge is contained at both ends the moment it jumps free of magazine. The sideways slipping cartridge base becoming vertically aligned with the bolt face, or more nearly so, ensures smooth transition.

And finally, adjusting the extractor is critical. I had to remove substantial material from 8mm extractor to make it work with much larger 404J rims. The curvature needs to be retained as the claw depth is reduced. Weibe's book suggests that the claw should just hold a fully loaded cartridge on the face of a bolt removed from the rifle. However, his book is about building 375. For larger calibers with much heavier cartridges, I submit that the claw should just BARELY hold a loaded shell on the bolt face. The weight of a cartridge will not necessarily determine the claw's ability to extract fired cases. If it takes a lot of effort to push a cartridge under the claw with bolt removed, you know it's liable to hang up during cycling. I also discovered if a claw is subject to too much spring tension, that will inhibit smooth cycling. The claw on my Mauser bolt had so much tension I couldn't remove the extractor from the bolt without serious prying with a screwdriver. Extractors should be removable with finger pressure. I relieved some of the spring tension by reshaping the extractor and it made a world of difference smoothing the pickup of cartridges from magazine during cycling. It also eliminated problems I was having with inconsistent snap over when dropping shells in the chamber manually. And I agree with Weibe, a dangerous game CRF rifle that doesn't snap over isn't much of a dangerous game rifle.
 
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A gunsmith friend of mine got so fed up trying to modify the feed lips on a rifle he was building ( continual interference from the customer didn’t help) that he removed the lips entirely and made an internal magazine for it. That way he could tweak them to how he wanted.
gumpy
 
A gunsmith friend of mine got so fed up trying to modify the feed lips on a rifle he was building ( continual interference from the customer didn’t help) that he removed the lips entirely and made an internal magazine for it. That way he could tweak them to how he wanted.
gumpy
If I could do it, surely your gunsmith friend could have handled it. My guess is he removed too much from the feeding rails. We have seen more than a few rifle build threads that involved donor guns wrecked that way. The last step I described above is where it's easy to make a critical mistake. Or, more correctly, making the last step the first step. The right rail must be modified first BUT with a fully loaded magazine. The natural inclination is to start modifying with only one shell in the magazine and work forward adding more cartridges. Modifying the left rail proceeds okay, but then when the magazine is fully loaded with three rounds, the top one won't stay under the rails. Oops. Too much metal was unknowingly removed in step one. And it's almost impossible to undo. The gun now becomes 2+1 instead of 3+1.

I think way too much is made of Paul Mauser's cosine 30 formula for modifying the magazine box. Yes, it's important, but only one aspect. As I discovered, following the formula precisely is not nearly as critical as many maintain. The steps for changing the rails and follower are, however, critical.
 
In the case I mentioned, it was caused by the client changing the projectile of choice combined with seating depth ( pointed to hydro seated way out to just fit the mag well) which changed how it fed, it went from feeding beautifully to mis-feeding or jamming and then I think he removed a bit too much trying to get it feed as the lift point had already been changed to suit the first projectile. The client also changed several other things with the build and then didn’t want to pay for them. There may have been a certain amount of "frustration " involved
gumpy
 

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