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If you had said 458WM, then I could offer my experiences...

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If you had said 458WM, then I could offer my experiences...

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Please offer away. I just bought one and it doesn't like feeding the super-x 510 grain much.

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Yes, that large round nose of the 510gn projectile gives problems in many Mauser action derived rifles.

Okay, the problem is that there is a large recess inside the action (right hand side looking from the rear of the rifle), where the extractor sits when the action is closed. (There is a recess on the other side also for the locking lug but it is not as big and doesn't cause any problems.)

The CZ magazine is staggered and those rounds coming from the left hand side only (which happen to be the "even" numbered rounds in the magazine) feed at an angle that points towards the large recess on the right hand side. The rounds with fat stubby projectiles get driven and snagged in this recess - only just but it's enough to cause a jam.

The relatively short length of the round accentuates the angle of the cartridge as it comes up the feed ramp, making it more likely to jam (the longer length of the 458Lott cartridge gives a lower feed angle and avoids the jamming issue - I believe this is why CZ USA automatically re-chamber the 458WM to 458Lott, and the rifles have both cartridge designation stampings on the barrel. CZ rifles sold in Australia come in via CZ USA).

One other way around the jamming issue is to modify the feed ramp to try and guide the cartridge towards away from the recess - not always successful though.

My 458WM was bought as a new rifle by someone else and they had the ramp modified, without success. The owner got a refund from the dealer, as a warranty issue, and the dealer was then going to part the rifle out (get more money this way) - I ended up buying it cheap before this happened. I was going to fiddle around with spacers in the magazine (not sure if this would've worked) but ended up just using the Woodleigh 400gn PP - their spire shape avoids the jamming 99% of the time.

I can clear the jam quickly now (the remedial action is just like "fretting" a guitar). I would not, however, rely on it if I was going to hunt something large and angry, but it is fine for BGR competition.

Note that even in the Brno 602 days, you had a 50/50 chance of getting a 458WM that would jam - only this cartridge though.

Edited by mauserand9mm (13/06/14 01:04 PM)

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....p.s. I am also curious as to why I can fit more rounds into my ZKK602 than can be fitted into the CZ550s. My .375H&H holds six (6) rounds in the magazine!

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....p.s. I am also curious as to why I can fit more rounds into my ZKK602 than can be fitted into the CZ550s. My .375H&H holds six (6) rounds in the magazine!

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The 375H&Hmag and 458WM CZ550s will hold 6 rounds in the magazine, but both are specified at 5 shot capacity.

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On a 375/458 CZ and Brno, when the action and the bottom metal are fitted together with the magazine box tight between them, you can usually barely squeeze a sixth round in, but not close the bolt over it. Some CZ stocks are generously dimensioned internally, and there is an additional 1-2 mm of play for the magazine box. That's why in some 602 and 550 you can fit six rounds.

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Philip

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....p.s. I am also curious as to why I can fit more rounds into my ZKK602 than can be fitted into the CZ550s. My .375H&H holds six (6) rounds in the magazine!

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The 375H&Hmag and 458WM CZ550s will hold 6 rounds in the magazine, but both are specified at 5 shot capacity.

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On a 375/458 CZ and Brno, when the action and the bottom metal are fitted together with the magazine box tight between them, you can usually barely squeeze a sixth round in, but not close the bolt over it. Some CZ stocks are generously dimensioned internally, and there is an additional 1-2 mm of play for the magazine box. That's why in some 602 and 550 you can fit six rounds.

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I hadn't really though about it but that makes sense. I'm sure I can close the bolt over the 6th round, but there's no room left to try and squeeze a 7th under the extractor for 6 in mag + 1 in chamber.

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