Thread: ZKK-600 7x57 Hard to chamber

I have just finished a prolonged “restoration” of a dirt cheap ZKK600 in 7x57 I picked up on the premise the bore was near new and was otherwise in perfect serviceable order, I’ve done all the work, stripped it, cleaned it out and removed all the crud ect, today I went to go and pop some rounds through it and had to smash the bolt home and bash the handle down to chamber a round.

This was with supplied ammo, so I whipped home and grabbed a box of PPU to eliminate the dodgy ammo factor, and same thing again, and did it again on fresh S&B

It’s just as bad to open it, beating the handle open, and having to palm smack the bolt back.

Definitely 7x57/7mm mauser in a 7x57 marked rifle, factory barrel matches receiver, bolt is correct and in spec, chamber and bore are excellent, and I had cleansed chamber of carbon and scrubbed inside very very throughly to the point I can’t get anything on a clean white cotton cloth.

Ultimately decided not to shoot it and ask around before deciding what’s next.

Are these BRNOs known for a tight chamber, as I’m totally stumped because clearly it’s been well used.

Is the bolt assembled correctly and it works fine without a round trying to chamber?

Originally Posted by No.3

Is the bolt assembled correctly and it works fine without a round trying to chamber?

Yes, there was absolutely no hint of an issue until I tried live rounds

Any chance it’s a replacement barrel, albeit the correct one from another rifle.

Take a factory round coat it in engineers blue or black felt marker and gently chamber it stopping when there's definite resistance remove and see where it's binding. Failing that take a chamber casting, sulphur and graphite works well and compare it to the Sammi specs.

I just tidied up my mates grandads rifle, brno zkk 600 7x57.
It has a tight chamber too. Factory Federal 7x57 is hard to chamber. We pulled the loads, bumped the shoulder back and upped the charge 2 grains to get decent velocity from it (was 2440fps and now 2650fps.)
I've set my mate up to handload for it using my gear now.

Are you chambering from the magazine, or just sitting on the mag follower? They have a Mauser extractor so the rim needs to pop up behind the extractor as it comes up from the mag.
Chambering when the round is sitting on the follower may not allow the extractor to bend and pop over the base of the cartridge into the extractor groove.

Originally Posted by Plinky

Any chance it’s a replacement barrel, albeit the correct one from another rifle.

This is my first BRNO center fire, so I’m not entirely sure although the wear is consistent across barrel and action, and the amount of crud below the woodline across the barrel and action would lead me to think it’s the original barrel, but don’t quote me.

Originally Posted by stug

Are you chambering from the magazine, or just sitting on the mag follower? They have a Mauser extractor so the rim needs to pop up behind the extractor as it comes up from the mag.
Chambering when the round is sitting on the follower may not allow the extractor to bend and pop over the base of the cartridge into the extractor groove.

Yes it’s tight in the magazine, ie 5 rounds or one, I still need to smash the bolt forward to pick up and seat.

Strangely it’s smooth as butter empty.

Magazine floor plate and internal well are both marked “7x57” and are BRNO parts.

Originally Posted by Marty Henry

Take a factory round coat it in engineers blue or black felt marker and gently chamber it stopping when there's definite resistance remove and see where it's binding. Failing that take a chamber casting, sulphur and graphite works well and compare it to the Sammi specs.

Copy that, I’ll give that a go tomorrow and post the results.

I’m assuming it’s a case of identify and remediate each time until it’s not needing to be forced in ?

I should add the rifle is 1971 dated on the barrel, and has all correct BRNO markings, bolt and receiver match and all metal work is original, the only non original parts to the rifle is the stock, and FSP although I doubt that has any part in the problem.

Greetings,
Some metric cartridges like the 7x57 and 6.5x55 vary in specs between the US and Europe, especially in terms of headspace. A handloader may be able to help with tracking the problem down.
GPM.

My hunting mate has a very similar vintage Brno 7x57 and it's 100% normal in chambering and general function. Bloody accurate too I might add.

Please refrain from banging,bashing and otherwise forcing your precision instruments. Find someone with dies and sort the issue. The felt tip coloured case is first port of call. The only other possibility I can think of is bit of crud on front of chamber...a coloured round should show this up too.

IF it's found the shoulder needs a tiny bump back....I wonder if you could do so by removing guts/ expander from say a .308 die and giving it slight nudge with that??? Haven't compared shoulder angles or case fatness via specs but it might just be enough to work??