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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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