Out of curiosity what's the biggest caliber a CZ550 Magnum action can handle comfortably without opening the bolt face too much?

Well, this is an answer sort of. I have a 550 in .505 Gibbs and I will say that the remaining rim on the bolt face is thin, real thin. It obviously works, but it does not leave much metal. The diameter on the .505 is 0.6402".

Thanks so I would assume a .416 Rigby would leave enough metal?

Absolutely. Plenty of metal on the rim for a .416 Rigby. Cartridge rim diameter is 0.5902" on the Rigby.

Many thanks MJines.Happy Hunting!

While the .505 Gobbs bolt fact may be the limit in that dimension, I believe you can go up to the 600 Overkill. As MJines says, the .416 Ribgy fits and CZ also offers the 505 Gibbs and 500 Jeffery.

American Hunting Rifles can probably tell you a lot about the limts of the CZ, or you could post this same question in the Big Bore section here at AR.

The 600 OK is rebated down to the same rim diameter of the 505Gibbs. Thats the limit and both are the same. The 585HE (577Hubel) is the largest NON-REBATED ctg that CZ550 can handle. The 585HE also used the 505gibbs rim diameter.

I have the 505Gibbs and the bolt face looks ok to me. But, clearly at the limit.

Here is the CZ link, you can see for yourself.

http://cz-usa.com/products/vie...rican-safari-magnum/

http://cz-usa.com/products/vie...-550-safari-classic/

You can go to a .600 Overkill. Past that, no rim left on the bolt!-Rob

So, I would assume that with very little rim left on the boltface that it would break off sooner or later?

quote:

Originally posted by lal:
So, I would assume that with very little rim left on the boltface that it would break off sooner or later?

It will if you drop it on a concrete floor or rock, or hit it spot on with a hammer.
So could the .416 Rigby bolt face rim, but less likely damaged inadvertently.
Functionally it is low stressed and should not be a problem as long as the lockup of the bolt lugs is good.
Not ideal, but it works for the .505 Gibbs rim diameter.

It wont break off by itself! Ever! There are near 100 .600OK's out there now on CZ550's and no one has had a problem including those who actively hunt in Africa with them. Non existant problem IMHO.-Rob

quote:

Originally posted by lal:
So, I would assume that with very little rim left on the boltface that it would break off sooner or later?

Why would you make such an assumption?

The .500 Jeffery is perfect.

Ive noted that several custom made actions have a fractionally larger bolt, 0.7500 as opposed to 0.7000 (I think thats correct?)

just whose bolts are that size?-Rob

quote:

The .500 Jeffery is perfect.

This cgt it highly REBATED and SHORT (no neck) to the point it will fit in a STANDARD action. Thats the whole point of the 500Schuler. The 500J, aka 500Schuler, is perfect for any standard 30-06 length action.

I know it can handle 505 Gibbs. I think it goes
into the 600's.

I know that the 550 Action has the 505 gibbs
And cz also has some other big bores That start 600 I can't say what they are. They used have them on the WEB

Thanks chaps for all the info. That settles it: the CZ550 Magnum action is suitable for the really big bores!

One little thought.

If you are going to be screwing on a new barrel anyway, start with a rifle that was built with a smaller bolt face. Then your gunsmith can open it up just enough for your new caliber.

I have a CZ in .416 Rigby. Less than ten years ago I paid $599.00 USD for it! Anyway, the 416 case fitted a little loosely against the bolt face. I had to tweak the extractor to hold the cartridges and empty cases tightly to the bolt face. Nothing bad there; this is a mass produced rifle, so CZ makes things a little on the loose side.

For a custom 505 Gibbs say, buy a .416 Rigby, sell the barrel and have your gunsmith open the bolt face just enough for 100% reliability in controlling the Gibbs cartridge (with a little grinding on the extractor - buy an extra one or two). You will have a tiny bit more rim left on the bolt face, and the cartridge and casings will be held very securely.

Several of the newer manufacturers provide .750" bolts - Surgeon Rifles and Actions, RPA (in their largest sized Quadlock action), Pierce engineering, and others.

I believe only, and do not recall for sure, but IIRC the smaller concerns that produce CNC milled magnum square bridged Mauser type actions use ,750" bolts on their largest models. I am thinking of Prechtl, Empire, Martini & Hagn, and the fellows in Germany whose name is just past the tip of my tongue.

FWIAW

Edited for spelling.

quote:

so CZ makes things a little on the loose side.

I dont know, just spitballing - sometimes a loose fit might be more relaible feeding? Dont know, just wondering at the keyboard. Thinking about the lessons of the AK47, eating dirt and kept on shooting. You are probably right,... though ... cannot go wrong, I suppose, if a good gunsmiths set it right.

Well, their barrels surely do not fit loosely in their actions!

The slight bolt face looseness in the bolt face/extractor assembly is to accomodate the various rim diameters of different brands/lots/runs of brass.

I have measured Norma, A-square, Jamison and Hornady .416 Rigby brass. There were significant differences, to be sure.

When loading for yourself, and for use in one rifle only, pick a brand of brass (hint, in USA, order Hornady; overseas, order Norma or fress Kynamco cartridges. Then have you gunsmith open the face of a seperately purchased .375 H&H bolt. He can open the face, and grind and tweak two extractors so that you have a 100% perfect fit, in that one rifle.

Off track, but then you can adjust the stock length to fit you well, and cut the barrel back if needed for perfect balance.

From their, your artistic sensibilities and wallet are the only limiting factor in turning a very practical rifle into something pretty special.

Fourbore is alluding to an excellent concept. For a working DG rifle ther has to be a touch of slop to allow for sand, grit, mud, mud daubers, a hurried bolt stroke, a non-perfect cartridge case and a large animal bent on your distruction.

I had a .308 Winchester rifle that was worked over 50/50 by myself and a very knowledgeable gunsmith. When fired cases came out, there was no need to f/l resize them. There was no stretch to the cases at all. A quick pass with a carbide collet and it was reload and go time. The reamer was the 1995 Palma pattern. With occaisional and moderate cleaning the rifle was downright spooky at how precise and accurate it was out to 600 meters. This in a self bedded Remington varmint stock with the full length alumminum frame.

One day I pulled a cartridge rom the wrong carrier, It was pretty tight to chamber, but in the heat of the moment I got it in there and hit the 20 ounce soda pop bottle at 600 yards.

It would not open easily at all. I smacked the bolt handle as hard as I could with my right hand. The handle flew about thirty feet. When the smith got the case out and tig welded an after market handle on, the rifle was just as accurate. But, that rifle was never a "tactical" or "sniper" grade machine. It was too tight by quite a ways. My God son uses it for target practice. He is not allowed to ever take it over to SWA on a tour. I hope he listens.

I guess the above analogy hold true in spades for a DG rifle. It has to feed, fire and extract without fail - ever. The balance of tolerances is where a truly gifted and experienced gunsmith comes in.

There are some supremely talented gunsmiths in the USA, RSA, Australia, Germany, Austria, Belgium and England.

Good luck on your adventure with the 505 Gibbs. Get you tooth fillling and crowns checked first. Also, an X-ray of your cervical spine to check for spurs would not be out of line.

Enjoy