I am having a .510 JAB (.500 A-Square IMP, 50 Peacekeeper, .510 Wells, ect) built on a CZ-550 action and am definately looking forward to it. However, with the Mark X actions soon to be released, I am looking for a 'shorter' round that uses a .510 BMG bullet and can hold a few in the magazine.

I prosed the question of a .416 Rigby cut at the shoulder (2.37") with a .510 BMG bullet seated on top of that for a OAL of 3.68" with a look similar to a large 30 carbine. This way you could use a CZ-550 in .416 and get a new barrel & chamber cut, headspace it (this is where I ran into trouble which ultimately deep-sixed the project. Large round headspaced off the case mouth = bad idea) and you're done. If anyone does make this, I called it the .500 Oxen. Enough of that...

My questions are these:

1) Where can I get Pic's of a .495 A-Square and what are the case dimensions? Hopefully in comparison to a .500 A-Square.

2) What rounds in bullet sizes of .510 can be fed from a Mark X or CZ-550 mag with BMG (Not necessarly match, ie. A-Max) de-milled bullets? .510 Wisper? Others?

3) What velocity with 650gr and/or 700gr bullets can be expected for the .495 A-Square, .510 Wisper, others?

Thanks

ps. This is the best pic of a .500 A-Square I've found. www.firearmslinks.com/500asquare.html

You need the A-Square manual, which Sinclair International and amazon.com both sell. The manual has cartridge drawings for both and loading data.

Although it is possible to modify a Mark X to feed the 495 A-Square, that is a very serious project best undertaken only by a very qualified big bore expert. And then when you get done the action will have cost you triple the cost of the CZ550. I don't mean to discourage you, but be prepared. As far as max length, I believe you will find that both the Sunny Hill and Ted Blackburn extra deep magazine boxes for the Mauser action max out at 3.65" OAL.

Hi BMG,
That is a nice picture that reminds me of home. I usually seat those Hornady A-Max 750 grainers out to a full 4.75" (so as not to crowd the powder space) in the Ruger No.1 with long throat, and stick to milsurp and hunting bullets with the BRNO bolt action.

500grains is right about the Mark X action. It is really not suited to such a cartridge, though it could be done at a lot of expense and weakening of the action too.

The easiest thing of all is to use a Ruger No.1. Just rebarrel a 416 Rigby and remount the quarter rib on the new barrel, or get a picatinny rail machined to fit the new barrel, and you are ready for 1000 yard plinking with a portable piece.

The CZ 550 is the best pick for a bolt action for the versatile .510/460 cartridges.

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Good huntin' and shootin',
RAB

The photo shows a necked up .460 case. It has not yet been fireformed. Once done the case has almost no taper (0.013") and a very sharp tiny shoulder, it is a distinctive look.

Very true, Roger. I use 110 grains of IMR 4350 with that bullet, or any milsurp ball of lighter weight, seated out a bit farther, to fireform. Still reminds me of home, even if not completely formed yet.

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Good huntin' and shootin',
RAB