I would like someone on the forum to please explain to me, how I can obtain (purchase) a 500 A-Square rifle in a CZ model. I looked on there web sight and they only should it in a .458 Winchester magnum as being the biggest big bore offered.

You buy a CZ 550 Magnum in 416 Rigby and then send it to somebody to make it into a 500 A-Square. To the best of my knowledge, nobody is making a rifle for this "wildcat" cartridge. Good luck. Ming

T/jazz, you can buy a CZ in 416 Rigby and then send it to Pac-Nor Barreling or McGowen Rifle barrels for a new barrel. Both of these barrel makers chamber the round.

Actually it is not a very good idea to make a 500 A-Square based on an action set up for the 416 Rigby.

The 416 Rigby has a .590" rim, while the 500 A-Square has a .579" rim. When used for the 500 A-Square, the 416 Rigby has 0.011" of slop. A CZ550 bolt set up for the 416 Rigby will not even hold up a 500 A-Square round under the force of gravit, although it will hold up a 416 Rigby.

The consequence of this slop is that if you get a stick case, the extractor is MORE LIKELY to pull off the rim of the case. In a dangerous game rifle, that would be undesirable.

Some may think that a gun with that much slop in it is "good enough", but I would prefer to do the job right. Get a CZ550 in 458 or 375 and have it opened up to the right dimension, instead of starting off with something that is oversize and will give an inferior result.

I've built a fully funtional 500 A2 from a CZ 416 Rigby action and I can tell you without a shadow of a doubt that there is ABSOLUTELY no problem with Feeding or with Extraction.( See my posts and Pictures). I would not hesitate for one second to use this rifle on dangerous game and plan to do so this August. I can also supply pictures of the groups the rifle produces. You need to carefully consider things like barrel diameter and length as well as the need for a second recoil lug and a muzzel break. The final problem is a stock that will work with the large barrel channel required for a #7 or #8 contour barrel. Depending on your level of experience you may consider adding Mercury recoil reducers to the stock. Do not build one of these rifles too light as the recoil is substantial. You can E-mail me for details if you like .-Rob

Thank you all guys, there seems to be a little difference of opinion between personal, but I will work the facts out by calling a couple of those barrel makers.

I looked at the figures and I like the way that 500 A2 does things on paper ballistics wise. I am sure it would handle big animals with the same distinction.

Rob,

There is no question that a 416 rigby action will work for a 500 A2, but the excess tolerances on the boltface and on the extractor increase the chance that the extractor will pull off the rim. That probably won't happen in the living room, but it might happen in the field at 105 degrees after the ammo gets dropped in the sand and dust.

Why take a chance? 'Tis better to do it right.

500 grains- I think you don't quite understand how the cartridge to bolt face dimensions actually work. The difference in the rim diameter of .011 between the Rigby and 460 weatherby is insignificant. If you carefully measure the difference between most magnum boltfaces and the cartridges they feed , you will find some that approach this value. Without some excess in the rim dimension, I assure you that a cartridge will not slide up under the extractor and center on the bolt face properly. Now, I would rather have about .005 excess, but .011 works fine.
The bigger concern is that the rim thickness of the WBY and Rigby differ by about .002-.003 inches and sometimes more and it is this difference between the depth of the bolt face and the extractor that could result in a loose fitting cartridge. This will also vary between brands of cartridges. This is easily corrected by any gunsmith worth their salt. I would also have to say that many many people do not realize how critical the bolt face depth actually is to the proper feeding of a claw extractior rifle. As I've said before and proven, converting a CZ550 to 500A2 is easy and reliable. Also anyone competent enough to build or have built a gun like this will be a smart enough and experienced enough reloader not to take ammo to Africa that could stick in the chamber,I would imagine.-Rob

Actually the claw extractor doesn't care about the diameteral difference but the radial difference. The radial difference between the Weatherby and the Rigby is only 0.0055". This is not significant. I agree with Rob that the rim thickness is more important at least it seems more logical.

Casey

If I take the bolt out of a model 98, a model 1903 or a model P17, and if I slide a 30-06 cartridge in between the bolt face and the extractor, the rim snaps into place nicely and I can point the bolt any direction and the cartridge will be firmly held in place by the extractor.

If I do the same with a 500 A-Square cartridge on a CZ550 416 rigby bolt, the extractor will not hold the cartridge firmly against the bolt face. I had assumed this was due to the excess radial dimension. Perhaps it is due to the difference in rim thickness as Rob mentioned. Rob, after the extractor is adjusted to account for the difference in rim thickness, does the cz550 bolt hold a round of 416 rigby firmly, or does the cartridge fall away from the bolt under the force of gravity as with the un-modified extractor?

Also, what would be the disadvantage of starting with a 458 or 375?

The adjustment of the extractor is realatively simple and will hold the cartridge. However, in my experience it is not necessary that the cartridge be held firmly, only that there is enough ectractor metal over the rim to give positive extraction. This is because the chamber acts as a guide for the cartridge. Even a loose extractor to rim fit will still provide positive extraction and ejection.The bigger problem is proper feeding in which the critical bolt face to extractor dimension is often overlooked. The problem with starting with a .532 boltface and enlarging to .590 is that the bolt face will need to be opened and depthed properly, the extractor will need to be reshaped and fit and the mag box won't work. This will be a bigger problem in my mind. In addition there will alsobe considerable rail work involved. -Rob

How do you set the extractor back to account for the difference in rim thickness between rigby and 500 A2?

500-grains-The easiest thing to do is remove the extractor from the bolt and heat the claw to a dull red color with a jewelers Oxy-Acetylene torch and then bend it carefully to fit. I use needlenose pliers. If you use lots of heat control paste and metal clamps as heat radiators just below the lower bolt ring of the claw you may not effect the spring steel of the rest of theextractor at all. I did my CZ550 extractor that way. It rarely takes more than one try as you only need a few thousanths to give the claw a tight fit. If I suspect the metal has annealed then I re-treat the whole thing. hope this helps-Rob