I would really like to add a CZ 550 Rifle at some point and the caliber options are slimmer than with some rifles. The original choices I considered were .270 and 6.5 X 55mm. The .270 could serve as the one gun for the lower 48 as could the 6.5 X 55. One thing about the CZ 550 in 6.5 X 55, is the slower twist that CZ uses; it's 1 in 8.7. About 1" slower than typical.

Also in the mix, I have been hearing exceptional things about the 6.5 X .284, now the Norma. So it dawned on me that the CZ 550 could be reamed from 6.5 X 55 to 6.5 X .284 Norma. I know ammo will be limited, but I will handload it anyway and this may be the closest we get to a short action magnum in .264. Nominal twist for the cartridge is 1 in 9, so by handloading the 6.5 X .284 I don't see the 1 in 8.7 as a problem. The boltface would be slightly large for the 6.5 X .284, but we're talking .480" rather than .473" and likely the only potential problem, but I see it as slight. The standard action length, I feel, would be worthwile so there would not be the restriction for cartridge length, much in the same way that applies to 6.5 X 55 SM, which with data for strong modern rifles could fill the bill, but I like the idea of having something a bit different and a rifle that has potential to use the range of bullets from the 85 grain Varmint type to the very high sectional density 160 gr. pills.

What are you're thoughts on the possible conversion and who would be your recommendation for the reaming?

I haven't looked at a CZ 550 so I don't know if this will be a factor. The body diameter of the 284 case is slightly larger and the taper of the case is different. This may translate in different "timing" of the release of the cartridge from the magazine. Try some 6.5x284 ammo in the magazine and see if there are any obvious feeding problems. This would be the only thing I can think of that would require any work. Let us know how well the conversion works.

OEH, I believe the larger diameter and slightly longer body of the .284 is why reaming to 6.5 X .284 might make it an excellent conversion. I could probably do the reaming, but I want the utmost in precision if I have it done. The larger boltface of the 6.5 X 55 SM would however .007" of potential "slop", but I have no way of knowing if there will be any deterence to lock-up/accuracy until I do have the conversion done. Theoretical at this point, but very possible. Barrel steel quality of the 23.6" CZ barrel is excellent so I don't want to re-barrel. If it wouldn't work, I would probably just opt for a factory rifle and at this point, I'm guessing that might have to be a SAKO 75, since the cartridge is being loaded by Norma. Maybe the TIKKA, I haven't checked.

KLN357,
My cz 550 feeds 6.5x.284 Norma rounds flawlessly without rail modification, but the magazine box will only hold 3 rounds.

Wes

quote:

Originally posted by KLN357:
The larger boltface of the 6.5 X 55 SM would however .007" of potential "slop", but I have no way of knowing if there will be any deterence to lock-up/accuracy until I do have the conversion done. Theoretical at this point, but very possible.

I believe that what is sometimes mistaken as an incipient case head seperation problem is sometimes simply the result of less than perfect alignment of the blotface to the chamber from a blotface that fits the case quite snugly. The result is that the bolt will cock the case to one side just a bit and then the fireformed case will appear a bit lop sided @ the case head. This can be corrected by simply opening up the bolt face just a tad and shouldnt cause any problems as the chamber, (as long as it is tight), will hold the case in correct alignment. As long as it feeds and extracts properly I wouldnt be too concerned, correct alignment of the case is only the job of the bolt as far as its face is concerned. A tight chamber will take care of the rest.

The only other caveat to such a situation would be the possibility of case head swelling, but if that happens then your loading too hot anyway and need to back it down.

Thanks to everyone for your replies.

WESR, have you already done this conversion? If so, are you getting the kind of accuracy that is being touted for the 6.5 X .284 Norma?

KLN357,
No, I haven't done the conversion, but I have a 6.5x55 CZ 500 and a different rifle in 6.5-.284 Norma. I have put the Norma rounds in the CZ because I was interested in the exact same thing. The Norma rounds actually appear better timed in the CZ 550 action than the 6.5x55 rounds do. They pop under the extractor at around 1/4-1/5 of the bolt throw and line up perfectly with the shoulder of the Norma rounds hitting the chamber walls.

In my cz, all it would take would be to run a Norma reamer into the chamber to clean it up.

My 6.5-.284 Norma is a Dakota 76 (offered as a factory chambering) and will consistently shoot 5 shots with MOA groups with bullets of 140 grains or more.

Wes

Thanks WESR, That's great news. I am really sold on this cartridge and Ramshot powder that looks perfect for it. Plus I can get the rifle I really like!

Thought I would update. I just received a 2005 CZ-USA catalogue and the 6.5 X .284 is offered for the 550 through the custom shop!