Thread: ZKK-600 7x57 Hard to chamber

Is there a chance that this rifle is a 7x57R? and would that present a head space issue?

My last BRNO (.270) was 45 years ago...so maybe memory is fading a bit...but in the photo of the bolt with case sitting in it, there seems to be a lot of space between the rear of the case and the bolt face. I can see a lot of space/shadow back there.
Almost as though the extractor claw is clamped in nicely, but stopping the case from seating right back on the bolt face.
Or is that just a camera angle giving a false impression?
How about the bottom lug on the bolt...does the front action screw come up into the lug area and that screw too long (or stretched from years of being heaved tight) is jamming on the outer area of that bottom lug? That outer area is hidden by the extractor claw when you remove the bolt. Spin the claw out of the way and check the lug for gouges?

Could it be a bit of fuzz where the bolt lugs sit when close (don't know the technical term for those) maybe when no ammo there is enough room for them but when on a round it binds up. you could try a bit of lube on the lugs and see if it helps

I think those pics are of Micky Ducks bolt face

Originally Posted by 7mm tragic

I think those pics are of Micky Ducks bolt face

Here is mine for anyone interested, looks in line with a well used 53yo rifle

Originally Posted by 7mm tragic

I think those pics are of Micky Ducks bolt face

It's also a random 270 round sitting on 308 bolt lol... But it does show what it SHOULD look like.

So pretty much the same as mine lol.

For clarity - is it feeding cartridges with difficulty from the magazine, or just hard to chamber - close and open the bolt on? (Or both?)


First thing you do - is shoot it. If the empty case then extracts normally - try then and rechamber one of the fired empty cases. If it goes in with ease, then you will have a slightly have an out of spec chamber. This is fine, just means you need to reload after "fireforming" your brass in the rifle.

If it extracts with ease, but then is difficult to chamber the empty, means you probably have a slightly out of round chamber. (To prove this, it will chamber better, if you keep turning it around till it "fits" again.)


If you have issue with feeding from the mag, you can look at the usual suspects -

Mag spring too strong.(Try running a cartridge out of the mag with the floorplate dropped (held in your hand) a cm or so lower, to weaken the spring. If it goes in alright then, you need a weaker spring.)
Or, change followers with a Mauser and see if it feeds better.

Examine - Slide a cartridge forward slowly and see where its going wrong. Some might feed ballistic tip spitzer bullets well but not rounder nose soft points. You will have to see what it is doing. Is it releasing too late from the mag, it the bullet face planting on the side, or top, of the chamber.
Rough feeding ramps, you can smooth/polish with a stone or fine file. Smoothing only, you dont want to change any angles yet...not until you absolutely have to and you have to know exactly what you are trying to achieve.


NOte: There is no "mismatch between Euro and US cartridge specs" for this cartridge. Anyway, the rifle was made in Czechoslovakia, the Sellier and Bellot is made in Czech Republic and the PPU is made in Serbia. All European. (There is however, a difference in extractor groove depth on some old 7x57 PPU cases. Some older Highland/PPU cases will not fit standard shell holders and could be contributing to a difficult chambering.)

A video would be helpful to see what going on.

Originally Posted by John Duxbury

For clarity - is it feeding cartridges with difficulty from the magazine, or just hard to chamber - close and open the bolt on? (Or both?)


First thing you do - is shoot it. If the empty case then extracts normally - try then and rechamber one of the fired empty cases. If it goes in with ease, then you will have a slightly have an out of spec chamber. This is fine, just means you need to reload after "fireforming" your brass in the rifle.

If it extracts with ease, but then is difficult to chamber the empty, means you probably have a slightly out of round chamber. (To prove this, it will chamber better, if you keep turning it around till it "fits" again.)


If you have issue with feeding from the mag, you can look at the usual suspects -

Mag spring too strong.(Try running a cartridge out of the mag with the floorplate dropped (held in your hand) a cm or so lower, to weaken the spring. If it goes in alright then, you need a weaker spring.)
Or, change followers with a Mauser and see if it feeds better.

Examine - Slide a cartridge forward slowly and see where its going wrong. Some might feed ballistic tip spitzer bullets well but not rounder nose soft points. You will have to see what it is doing. Is it releasing too late from the mag, it the bullet face planting on the side, or top, of the chamber.
Rough feeding ramps, you can smooth/polish with a stone or fine file. Smoothing only, you dont want to change any angles yet...not until you absolutely have to and you have to know exactly what you are trying to achieve.


NOte: There is no "mismatch between Euro and US cartridge specs" for this cartridge. Anyway, the rifle was made in Czechoslovakia, the Sellier and Bellot is made in Czech Republic and the PPU is made in Serbia. All European. (There is however, a difference in extractor groove depth on some old 7x57 PPU cases. Some older Highland/PPU cases will not fit standard shell holders and could be contributing to a difficult chambering.)

A video would be helpful to see what going on.

Where I’m at now is just very stiff locking and unlocking of the handle, at the moment that is my focus as the magazine spring can be dealt to later.

I made some progress today and now have it feeding in and out to an acceptable standard, just forceful up and down on the bolt to lock and unlock.

It seems to feed and lock the fat nose S&B far better than the longer PPU rounds, although it still is to tight with the S&B for comfortable use and that is only after a massive amount of cycling rounds in and out all evening.

I have tried all other things suggested thus far, and I am at a loss as the results are contradicting.

I’m tempted to just get it re reamed and checked and specd by someone who knows these well, it owes me peanuts so far….

Prehaps it was just a Friday afternoon rifle ?

Shoot it. Before you do anything else including send it to a gunsmith - shoot it. If you can close the bolt on the cartridge you cant go wrong. (MD These rifles in 7x57 have a long throat so its unlikely to be a cartridge OAL issue, and pressures will be low.)

Then you can check your fired brass. Look, I am betting if you shoot it the fired cases will chamber fine afterwards. You will have a tight chamber or slightly out in some way.

This kind of thing is not uncommon with BRNO rifles of that era. I think their manufacturing ability depended on how inspired the workers were by the Communist songs played over the loudspeaker in the factory that day. I now refrain from buying old BRNOs unless I can test it in person that it feeds and chambers correctly. I demand proof of life. BRNO were bastards for making rifles that almost work properly. If you get them going they are great.

Ok so the shallow groove thing MIGHT just be it. Place a shell on bolt like in my photo and see if the extractor claw sits back flat against body of bolt or not...it it doesn't... you've found issue. Crap around lugs would be felt without a round chambered...

Nah don't ream yet.

Can you put up photo's of the outside edge of each bolt lug, the contact face of each bolt lug and also the third emergency lug and the cocking area of the back of the bolt (including cocking piece etc etc).

I'd have a good look in the action in the bolt lug recesses, and check for crap fuzz and junk at each of the places things need to meet. Also, carefully pop the extractor off and see if that's clean underneath the rim and where it retains etc to make sure it can seat fully back into place and isn't fouling the back of the barrel or something else stupid.

Even colour in the back of the bolt lugs and see what that looks like, and the front face of the extractor...

No marks on projectiles???

Greetings All,
I note the replies regarding the US and European standards being different, perhaps I should have said the adherence to those standards varies. In my safe is a T3 6.5x55. Lapua cases emerge after firing having stretched little. To me this suggests that I have a close to minimum chamber and the cases are close to max. Happy days. It all turned to custard when I started sizing. A Hornady headspace comparator and set of Redding competition shell holders were on hand which showed that I needed to use the +0.010" shell holder to get the desired 0.05mm (0.002") bump with my Redding FL die so the total set back with the standard SH was 0.3mm (0.012"). Perhaps my chamber was as loose as a goose. Wrong. Measuring fifed cases from a friends Ruger 6.5x55 showed it's chamber was even longer. Maybe my dies were duds so out with old Lyman FL dies from the early 1990's. Worse again.
In the US manufacturers are reluctant to adopt wildcat cartridges due to the baggage that comes with them and perhaps it is the same with overseas cartridges as well. For those of us that like the 6.5 and 7mm European cartridges it is just something we have to work through. For my T3 the +0.010" shell holder and for my old M38 with the miss matched bolt light loads and neck sizing should do. I can always set the Lyman of the shell holder if I need to.
Regards Grandpamac.
PS. The 6.5x55 is still my favourite cartridge.

Originally Posted by grandpamac

Greetings All,
I note the replies regarding the US and European standards being different, perhaps I should have said the adherence to those standards varies. In my safe is a T3 6.5x55. Lapua cases emerge after firing having stretched little. To me this suggests that I have a close to minimum chamber and the cases are close to max. Happy days. It all turned to custard when I started sizing. A Hornady headspace comparator and set of Redding competition shell holders were on hand which showed that I needed to use the +0.010" shell holder to get the desired 0.05mm (0.002") bump with my Redding FL die so the total set back with the standard SH was 0.3mm (0.012"). Perhaps my chamber was as loose as a goose. Wrong. Measuring fifed cases from a friends Ruger 6.5x55 showed it's chamber was even longer. Maybe my dies were duds so out with old Lyman FL dies from the early 1990's. Worse again.
In the US manufacturers are reluctant to adopt wildcat cartridges due to the baggage that comes with them and perhaps it is the same with overseas cartridges as well. For those of us that like the 6.5 and 7mm European cartridges it is just something we have to work through. For my T3 the +0.010" shell holder and for my old M38 with the miss matched bolt light loads and neck sizing should do. I can always set the Lyman of the shell holder if I need to.
Regards Grandpamac.
PS. The 6.5x55 is still my favourite cartridge.

The 6.5x55 does have some difference between Us and Euro specs, but the old 7x57, grandfather of everything, never has. The 7x57 is my favourite. (Along with the .30/06 - and also the .308! I am a very plain guy. But I have enjoyed reloading the ancient .44-40 the most over the years.)