The rim thickness of a 375 H&H is ~ 0.050" while the rim thickness of a 416 Rigby is ~ 0.062". Is the CZ 550 extractor used for the 375 H&H machined differently than the 416 Rigby to accomondate the rim thickness difference?

Thanks,
Axel

Axel---

They look to be the same part but the 416 has more bevel on the bottom for clearance during feeding.

axel. The commercial Mauser Werke extractor appears to have been 1.2 m/m thick on the lip before polishing the face (.0472") and .044" plus or minus after polishing. Brno (ZB and CZ) tended to keep to the same dimensions. Length of extractor OAL no consideration. The difference for the thicker rims was taken up by the bolt face distance from the breech face of the barrel. Brit Rules of Proof and CIP Max ctg dimensions are(rim-thk) .416 Rigby and .505 Gibbs .065"
.460 & 378 WBY. .063"
.308 Win .054"
8X68 .055"
8x57 Mauser .051"
.500 Jeff(Schuler) .404NE,
.300 & .375 H&H .050"
.30-'06 .049"
7X57 Mauser .0452"
7.65 Arg, Belg. Turk (cmcl.) .040"

Breech distance from avg, unmolested Mausers;
(Mauser Werke Mfg.)
Gibbs and Rigby .122"
8X68 (intended action) .113"
H & H .113"
8X 57, 30-06 (nominal) .106"
and most 7X 57's
7.65 Arg. Military .1045"

It is considered bad form to thin up the hook or the blade of the extractor ( not too smart either)

Lapping bolt lugs and lug seats of receivers means less need be removed from bolt face, and re-facing of the receiver breeching face adds to the ammount to be removed. It is advisable to follow the Mauser lead to avoid needless problems.
The longer ctgs had more bolt face cut back to lessen the ammount of entry bevel underside of extractor hook to allow for ctg. angle to extractor hook as ctg moved forward in movement out of magazine to chamber. (explanation for why the "math doesn't seem to check out)

Thanks gentlemen! How should I compensate for the increase in the bolt face to extractor distance when opening up a bolt face? I had planned on hard welding the extractor and recontouring; therefore regaining the desired distanced from bolt face to extractor. This would have the added effect of creating a thicker extractor. Is this the right way to do it? Is there a better way?

Thanks,
Axel

Axel- A great engineer like you should have been able to figure something this simple out yourself. Duh- you don't weld -up the extractor, you machine the bolt face to obtain the correct rim thickness dimensions. No that means you don't grind it, it means you lathe turn it with a Lathe tool. Yes it's a hardened bolt and you may have to aneal it first. carbide usually works, but not always. Your cutting into the case hardening in any event and you have to re- heat treat the bolt afterwards. Welcome to Big Bores!
This must be a moment of weakness, as GOD knows I have no reason to help you, but I just can't stand the thought of you welding up your extractor!-Rob

Robgunbuilder, when I face the bolt I will be removing material, thus increasing the distance from the bolt face to the extractor. With me this far? Since I wish to maxmize the grip, thus the extraction power, of the extractor to the case I want to minimize the loose fit between the cartridge and the extractor. Still with me? To accomplish this feat I need to tightly control the distance from the bolt face to the extractor, correct? In order to accomplish this it, seems to me anyway, that I either must add material back to the bolt face or to the extractor back face. By extractor back face I refer to the portion of the extractor, which directly contacts the rim of the case.

Do you understand what I am trying to do now? If so, do you have any advise other than reworking the extractor?

Since the rim thickness dimension has been set for a 0.065+" rim on the CZ550, the bolt facing method you describe won't work. For your information, I have a CZ550 375 H&H, and the distance from the bolt face to the extractor back face is 0.072". Rather sloppy in my opinion, particularly when you consider that the 375 H&H rim thickness is ~ 0.050". This particular rifle exhibits sticky bolt lift with any load you try.

It is not every round mind you just about every second or fourth or tenth round upon which the bolt is a pain to lift. This is undoubtedly due to the fact that most, if not all, of the extraction cam has run out of axial movement by the time the extractor engages the cartridge rim!

Thanks,
Axel

[ 04-23-2003, 23:57: Message edited by: Axel ]

Axel- I don't know what you've done to your extractor( no the old dremel on the underside isn't a good idea), but my .375 H&H CZ550 measures .055. To convert to a .416 Rim case, I and everyone else opens the boltface as described and doesn't weld up the extractor.
If your boltface to extractor dimension is .072, your .375' rounds will probably not eject, just fall back in the action and sit there, jaming the gun till you shake it loose. Why not just buy a new extractor?
I suspect the sticky bolt lift is not caused by the primary extraction cam( unless you've re-welded it)of course caused by your misreading of your loading balances resulting in sporatic overloads. Sticky bolt lift is usually a sign of impending personal injury. You sure you are up to this? - Rob

Robgunbuilder, the rifle was purchased new and has only been fed Federal ammo, NO RELOADS. I have purchased a new extractor and it is identical to the original extractor! I though perhaps CZ has sent me a 416 Rigby extractor, but Mr. Belk has stated the extractors are all identical and I believe him.

The sticky bolt lift IS due to lack of extraction power. The rounds eject but not very well.

Axel

[ 04-24-2003, 00:55: Message edited by: Axel ]

I made a mistake in an earlier post, as I was reciting from memory. The distance from the bolt face to the back face of the extractor on my rifle is 0.100", and I am planning on modifing the extractor to obtain a distance of 0.072".

I got the 0.072" dimension from two Winchester M70s and a M77 Ruger I measured. All three of these rifles fed well, and are chambered for belted magnums.

Again any ideas other than the weld up and recontour I would very much like to hear.

Thanks,
Axel

[ 04-24-2003, 04:36: Message edited by: Axel ]

axel. With "virginal" parts there is supposed to be endplay in the pure Mauser design extraction system. Extractor in place shoved to tail end of bolt there ought to be a minimum of .053 space between underside of hook and bolt face for the Magnum H&H and those in the .050 rim thickness category. Smaller rim dia. it can be less but NOT less than the max ctg listed rim thickness. The "case" on CZ andZB Brno's is thick enough that cutting with Micro Grain Carbide will machine the face and the face will be of sufficient remaining hardness to carry out the mission without additional hardening when taken out to Rigby and Gibbs diameter.
The end play- fore and aft movement is to help the empty "go around the corner" in ejection.
The bolt face rim surround extension is part of the design(Prong on Left lug side) There can be a hang up due to top of extractor digging in to rim inside face,and this part of extractor is usually rounded to prevent a cutting activity by the extractor.
Welding on this part of extractor is inadvisable because they ultimately fail, and that just when you need it most. Failure is in the parent metal adjacent to the weld. The endplay is in the retainer blade aft of the hook and the front face of it is on the same angle as the front face of the extractor groove in the bolt just aft of the face.
ECCENTRICITY; If chamber is not on center with the bolt face, turning handle up to start the process of disengaging from battery, will cramp the case rim and in excessive instances the brass on the rim will be ironed and spalled where the bolt head rim surround presses tightly on the rim in the turning activity. There will be a brass colored rub mark on the rim surround of bolt at the face, and powdered brass to boot in that area. Some times this can be alleviated with appropriate small abrasive wheel in the dreaded Dremel.( making that portion of the surround eccentric to accommodate).

To state yet again as noted in other's posts The rule is , Thicker rim, setback the face to corresponding ammount, and my previous post details how much Mauser thought proper.
To add insult to the problem, The extraction cannelure diameter for the H & H and the belteds of similar parentage varies. Winch brass is usually the largest, Rem the smallest dia. and Fed and Norma somewhere close to Rem. This acomplicates things for we be knighted members of the gunsmashing trade. If an owner is a purist and wants near perfect extraction and the ejected pile to be in a neat handful, one place on the ground,then he had damned well better stick to the Ammo brand it was set up for!
Ideally, the extractor tension should be enough to consistently grip the same brand ammo, the same way round to round and whatever brand used a competent working rule is to measure the distance radially from Lug to corresponding surface on the extractor straight accross, empty face(no ctg in place) then with the ctg in place measure again and this should be .004 to .006" increase meaning the extractor is moved outwards because of the case interference by the rimless groove in the chosen brand case by that ammount.
If set for Rem it will be stiff for Win. Simple as that.

axel. I had some additional remarks and a question about nitriding at low temps. Tried to get through the obstacle course to you & failed 4 times-19 hours ago and few minutes back. If you hot mail me from my profile address, might be an answer will make it. If you don't want such, please say so and I'll frag the mail. Thanx.

systeme98, my email addy invalid as I have let the account die. Send me a private message and I will help you out if possible. Thanks for the information regarding the setting up of a mauser type extractor. I am daffled by this CZ's extraction issues.

Axel

...10 grams of rel 11....

just so i can not be called for giving a bad load datum...

If it sticks, send it back, if it's new and only shot with factory loads.

period

don't start with a problem child