I need a new mainspring for a 243, ZKK 601; the original is weak. I can't find one.
Any ideas?

Place in AU shows they might have one.

Would a plain old Mauser spring work? Maybe with some mods? Try calling CZ USA customer service...maybe they could get you an original from the mothership? I've found the back office CZ folks very responsive.

Thanks I will call cz. I will check if a Mauser one will work; I have lots of those.
AU is Australia?

Yes AU, Australia the link showed parts for your 601 rifle

I got an extractor from CZ a little while back. Was here in just a few days.

CZ USA has none.
I'll just hand forge one.

How about a spring from the short action CZ 557. CZ may have them. With CZ parts dpt you really need to dig deep. Most of the time they aren’t aware of the parts they have in stock.

Wolff makes one for the 601 and I have one of those coming. CZ guy I talked to was clueless.

Tom, when I asked Wolff for a Brno 601 spring, they indicated Wolff only carried Springs for the Brno 602. Which spring did you order for the Brno 601, please?

602; I mistyped above.
One, two, a difference of only one.
I'll start calling them long and short.