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Shooting & Reloading - Mausers, Big Bores and others >> Big Bore Rifles
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mauserand9mm
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Reged: 03/09/09
Posts: 1003
Loc: Queensland, Australia
I split the stock on my CZ550 375 H&H
      #167917 - 17/09/10 06:47 PM

My fault - I knew I had to do something about it earlier.

I'd bedded the action and the rear sight recoil lug when I first got it. I also put bedding compund in the gap behind the tang - big mistake. I was warned afterwards that I should remove the bedding I put in behind the tang and that the gap was intentional and necessary.

As most oy you know, the tang acts as a wedge in this area so it shouldn't contact the stock at all.

Oh well, serves myself right. It only appears to be superficial as I coudn't see any signs of the depth of the crack when I removed the bedding material.

I would love to see high speed video of the tang area to see how much movement there is.

Good excuse to buy some nice timber? Why do I do this to myself? - I was starting to get serious about building a 500 Jeffery on a Ruger No. 1 for group 3 BGR. Is there something in my sub-conscious make-up that tries to keep rifle projects on the cards? I also shoot ex-mil Mausers (ParrallaxBill website regular) and have a Columbian carbine that needs a good stock clean-up (I've wanted to do this for some time but reloading seems to currently chew up my spare time).

Edited by mauserand9mm (17/09/10 06:56 PM)

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Ben
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Reged: 22/08/08
Posts: 1917
Loc: Northern Territory, Australia
Re: I split the stock on my CZ550 375 H&H [Re: mauserand9mm]
      #167918 - 17/09/10 07:39 PM

Well, it will look wonderful with a nice new stock. All the best!

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Mike_McGuire
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Reged: 11/06/05
Posts: 348
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Re: I split the stock on my CZ550 375 H&H [Re: mauserand9mm]
      #167927 - 17/09/10 10:03 PM

Quote:


I would love to see high speed video of the tang area to see how much movement there is.




When you fire the rifle the stock "balloons out" in the magazine area, which is why cross bolts are used to stop the stock splitting. When the stock balloons out then the stock in that section becomes shorter than the action. Thus the tang hits the stock material. Also the reason that there needs to be clearance around the action screws.

The mistake made by many people is to put one warp of very thin tape around the tang because they think the problem is caused by the action setting back a thou or two in the recoil lug area and thus very minimul clearance around the tang should be OK. When I bed rifles like Howa/Vanguard that also have a tang that will rest against the stock, I use 3 layers of masking tape around the tang and just folder over the bottom of the tang by a small amount. That way nothing has to be ground out after the bedding is done.

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Peconga
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Reged: 26/06/07
Posts: 19
Loc: Arizona USA
Re: I split the stock on my CZ550 375 H&H [Re: Mike_McGuire]
      #167963 - 18/09/10 11:41 AM

Mauserand9mm,

If you want to try again, I have an unfired take-off stock available for one of these. I had a project in mind for it, but had a change of plan. It's a nice looking piece of wood, with a straight comb, not the Bavarian humpback. Surprising that CZ made them with a barrel lug but no cross-bolt for the receiver lug; in my opinion they definitely need some reinforcement in that area.

Shipping from the USA to Oz shouldn't be too hideous; contact me by PM or email if you're interested. (Also have the complete triggerguard assembly available).


--------------------
Peconga in Arizona USA

Edited by Peconga (18/09/10 11:42 AM)

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Peconga
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Reged: 26/06/07
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Loc: Arizona USA
Re: I split the stock on my CZ550 375 H&H [Re: Peconga]
      #168052 - 20/09/10 07:01 AM

Here are some photos of the stock to which I am referring. It's actually very nice wood for a production rifle, with cut checkering and a satin synthetic finish. Inletting is very clean, but as you can see the primary recoil lug under the front receiver ring is comparatively shallow and unreinforced. Hence much of the stress from firing will be transferred to the rear of the magazine box, as well as the top tang, especially if the metal is bearing directly on the wood at that point. The recoil lug on the barrel is a useful addition, but by itself would not be sufficient. Personally, I prefer a big cross bolt through the stock under the front recoil lug for anything bigger than a .30-06 class cartridge, but even an aluminum block embedded with a bunch of epoxy bedding would be a big improvement over the factory design.






--------------------
Peconga in Arizona USA

Edited by CptCurl (08/10/10 11:27 AM)

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mauserand9mm
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Reged: 03/09/09
Posts: 1003
Loc: Queensland, Australia
Re: I split the stock on my CZ550 375 H&H [Re: Peconga]
      #168065 - 20/09/10 12:52 PM

What is the vintage of that stock?

The recoil pad reminds me of the Brno 602 style. The newer CZ550s also have a longer recoil lug block under the rear sight base.

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eagle27
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Re: I split the stock on my CZ550 375 H&H [Re: mauserand9mm]
      #168074 - 20/09/10 04:21 PM

If that were mine I would put in three cross bolts. One through the stock 'behind' the recoil lug, one behind the magazine cut out and one behind the trigger cut out. That wood does not look particularly dense and every cross bolt will help to eliminate splitting. This is how my original Mauser stock has been set up when re-chambered for 404J.

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mauserand9mm
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Re: I split the stock on my CZ550 375 H&H [Re: eagle27]
      #168079 - 20/09/10 05:09 PM

Quote:

If that were mine I would put in three cross bolts. One through the stock 'behind' the recoil lug, one behind the magazine cut out and one behind the trigger cut out. That wood does not look particularly dense and every cross bolt will help to eliminate splitting. This is how my original Mauser stock has been set up when re-chambered for 404J.



Do you have photos? I don't recall seeing a rifle with the third cross bolt behind the trigger before.

Earlier versions of the CZs didn't have the cross bolts but they added them as standard after some stocks cracked on the 458s and 416 Rigbys, I believe. I wonder where they cracked - was it at the sides of the magazine where the timber is thinnest? Anyone know?

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eagle27
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Re: I split the stock on my CZ550 375 H&H [Re: mauserand9mm]
      #168080 - 20/09/10 07:00 PM

Quote:

Quote:

If that were mine I would put in three cross bolts. One through the stock 'behind' the recoil lug, one behind the magazine cut out and one behind the trigger cut out. That wood does not look particularly dense and every cross bolt will help to eliminate splitting. This is how my original Mauser stock has been set up when re-chambered for 404J.



Do you have photos? I don't recall seeing a rifle with the third cross bolt behind the trigger before.

Earlier versions of the CZs didn't have the cross bolts but they added them as standard after some stocks cracked on the 458s and 416 Rigbys, I believe. I wonder where they cracked - was it at the sides of the magazine where the timber is thinnest? Anyone know?




If you go to Mauser Photos and Archives and have a look at the post "Mauser 404" you can see the stock with 3 cross bolts in the areas I outlined. (I don't know how to post the direct link)

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Peconga
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Reged: 26/06/07
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Loc: Arizona USA
Re: I split the stock on my CZ550 375 H&H [Re: eagle27]
      #168088 - 21/09/10 12:43 AM

Sorry, but I don't know the vintage of the stock; I've had it for at least five years. I also know that it was from a .375 H&H rifle, since it came with the original barrel and triggerguard assembly.

--------------------
Peconga in Arizona USA

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DarylS
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Reged: 10/08/05
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Loc: Beautiful British Columbia, Ca...
Re: I split the stock on my CZ550 375 H&H [Re: Peconga]
      #168125 - 21/09/10 08:07 AM

Crossbolts, fore and aft of the mag box on all kickers.

--------------------
Daryl


"a gun without hammers is like a Spaniel without ears" King George V

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mauserand9mm
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Re: I split the stock on my CZ550 375 H&H [Re: DarylS]
      #168130 - 21/09/10 10:18 AM

Eagle27, had a look at the photos and very well done - plugged with timber so they don't stand out in looks.

All,

I'm trying to grasp the mechanics of what is going on. Correct me if I'm wrong:

In recoil, the action metalwork will bend only a little bit. If bedded properly (at the front action screw) the timber will compress and deflect outwards (at the weakest point - the sides of the magazine well) as a result of force at the bedding point. The rear action screw does not provide any bedding support allowing the action metalwork to shift backwards in the timber (as it compresses). Lack of the tang "gap" will result in wedging and splitting the timber at that point.

The cross bolts are put at either side if the mag well to try and prevent bowing of the timber. What would be the purpose of the third cross bolt, effectively, in the wrist of the grip? Isn't the timber solid here?

I guess that, if there was insufficient clearance around the rear action screw and the stock, this could also cause splitting. Is this correct?

Does anyone have photos of stock failure where there were no cross bolts used at all?

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eagle27
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Reged: 24/01/09
Posts: 1124
Loc: Nelson, New Zealand
Re: I split the stock on my CZ550 375 H&H [Re: mauserand9mm]
      #168150 - 21/09/10 05:24 PM

Quote:

Eagle27, had a look at the photos and very well done - plugged with timber so they don't stand out in looks.

All,

I'm trying to grasp the mechanics of what is going on. Correct me if I'm wrong:

In recoil, the action metalwork will bend only a little bit. If bedded properly (at the front action screw) the timber will compress and deflect outwards (at the weakest point - the sides of the magazine well) as a result of force at the bedding point. The rear action screw does not provide any bedding support allowing the action metalwork to shift backwards in the timber (as it compresses). Lack of the tang "gap" will result in wedging and splitting the timber at that point.

The cross bolts are put at either side if the mag well to try and prevent bowing of the timber. What would be the purpose of the third cross bolt, effectively, in the wrist of the grip? Isn't the timber solid here?

I guess that, if there was insufficient clearance around the rear action screw and the stock, this could also cause splitting. Is this correct?

Does anyone have photos of stock failure where there were no cross bolts used at all?



The Mausers, by design, are pillar bedded so any movement involving the rear action screw and pillar could potentially cause splitting so a cross bolt next to this area is just a bit more insurance I suppose. If putting in the effort to cross bolt a stock more is best I think. As you observe with my stock, they can be done to be unobtrusive, not that I have any problem with the full metal look of exposed cross bolts, they do add to the workhorse look of a fine rifle IMO.

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