6x43mm CZ - comments wanted


November 8, 2007, 12:08 AM
After playing around with various iterations of the 6.5mm in an intermediate case (akin to 6.5 grendel) I decided to take a look at potential 6mm rounds in the same size class.

The ide was to see what sort of hunting round could be developed around a small action rifle like the CZ-527. In addition, it would be handy of the round would fit in the AR-15. Here is the latest result, the 6x43mm CZ


The cartridge is based on the Czech 7.62x45mm, and used the same case head size as the 7.62x39. Cases can be formed from 7.62x45mm, 6.5 Mannlicher-Schoenauer or 6.5 Carcano. Opertaing pressure is 4300 bar, about 62,000 PSI, the same as the parent cartridge. Loaded to 90% pressure, this round will (per QuickLoad) drive a 100 gn Sierra SPBT at 2900 fps from a 24 inch barrel. By comparison, 243 will drive the same bullet at 3029 fps at the same 90% peak pressure.

The cartridge has a 20 degree taper, similar to 223 and 308, and the same 35 degree shoulder found on the short magnum catridges. No consideration was given to long, high BC match rounds. This cartridge was intended to be a light hunting round. In that role, it can come within 100-200 fps of the 243 with bullets weighing 100gns or less.

Since I designed this round with the CZ-527 as the most likely platform, I am tenatively calling this the 6x43mm or 6mm CZ.

Comments are welcome.

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November 8, 2007, 12:17 AM
since i am not familiar with case demensions and pressures of the 243, how does it stack up in ; overall lenght, overall weight, powder capacity, neck length, etc.??? I love the 243, but something close with less bbl burn, and a tad less recoil would really be something to get behind.

November 8, 2007, 12:24 AM
Have you compared this to the 6x45mm? Necked up .223 from the AR. Was used for bench shooting until the .308 started becoming popular, and trumped it.


November 8, 2007, 12:34 AM
here's a comparison of some common cartridges:


November 8, 2007, 12:39 AM
I think that a 6mm-250 would be interesting

wouldn't fit a 527 though

November 8, 2007, 01:18 AM
6x45 uses the 223 case, which has a much smaller volume. By using the 7.62x45 case as a start, I get a a larger case capacity, and a rim size equal to the 7.62x39mm. Since rifles like the Remington 799 and CZ-527 are available in 7.62x39, nothing more than a barrel change is required.

Also, I don't think 6x45 can push a 100gn bullet at 2900 fps with reasonable pressure.

November 8, 2007, 02:28 PM
I think that a 6mm-250 would be interesting

I think you just described David Tubb's 6XC (http://www.davidtubb.com/6mmxc.html) cartridge.

November 8, 2007, 02:54 PM
The 6-43mm bullet seems interesting and I would love to have one to test. Just looking at the information presented and some past knowledge, I could defiantly see it as an alternative to the .223 in semi-auto hunting and military rifles. As I see it, there are 2 big advantages to using this round over the .223.

Improved accuracy- short "fat" cases allow for a very constant and fast powder burn... leading to better accuracy. This is evident by the whole class of short magnums that have recently been made including the 300 WSM, the .270 WSM and 7mm WSM, and the .325 WSM. Each of these bullets have a short fat case which helps to increase accuracy over the longer, standard round. Also heavy bullets are not effected as dramatically by wind and obstacles such as grass, branches and glass when flying down range. Light bullets at high velocity are easily deflected by very small obstacles like twigs on branches and glass in the case of a military/police use. The 6.5mm comes with a heavier bullet than the .223 which helps to maintain a shot down range in rough conditions.

More Power- A heavier bullet, at a marginally slower velocity will have more kinetic energy on impact than a light bullet and marginally higher velocities.

I do want all of you who read this to know I have not had the opportunity to shoot one of these rifles....and I really wish I could. For all I know Everything I said may be wrong, please let me know if you take issue with anything I have said because I would really love to learn more about this bullet and potential uses.

November 8, 2007, 04:04 PM
I just ordered 200 7.62x45mm cases. I will be ordfering reamers and case forming tool soon. This round looks to have enough potential to justify further research.

I'll keep everyone updated.

November 8, 2007, 04:45 PM
Good Luck and have fun !

November 8, 2007, 06:08 PM
I'm mostly focused on military rifle technology, but I think you've hit the nail on the head for a light hunting cartridge. I wouldn't completely discount high BC bullets, though, as you can seat them deep enough to still fit in .223 MOAL and they provide you with a nice flat-shooting advantage, which can be critical to a killing shot. It would decrease velocity but I think it would help you with shot placement.

Or maybe I'm just insane.

November 8, 2007, 06:21 PM
When you start moving on this I'd like to see this thread go up as a temporary sticky. Fascinating project and from a selflish point of view, one I can learn a lot from watching as it progresses.

Best of luck to you GunTech.


November 8, 2007, 06:39 PM
Why not go with the 6mm PPC? A pretty potent round that will save you a lot of trouble.

Unless of course you want to be diffrent

November 9, 2007, 04:43 AM
This round spanks the 6x45 purple, no question about that (http://www.loaddata.com/members/search_detail.cfm?MetallicID=917). I agree though, that it's pretty close to the 6mm PPC.

Just off the top of my head, necking it out to .257 might be a worthwhile endevour. Since the OAL is precluding VLD type bullets, a little more bullet weight and diameter would not be a bad thing for medium range shots on game, and the general lack of .257 VLDs would not be a handicap.

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