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The K1 Break action rifle (A project if ever I saw one!)
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Author:  Ovenpaa [ Thu Jan 16, 2020 6:23 pm ]
Post subject:  The K1 Break action rifle (A project if ever I saw one!)

Where to start…

Firstly, the pictures are at the bottom as I cannot wrap the text around them.

This rifle came in from an RFD on the south coast. Apparently the owner had pulled it apart for reasons unknown, lost some parts, then lost interest, shipped to the RFD who shipped it to me with the plan of returning it to working condition.

It very quickly became apparent that there was a lot of work required including:

Replace the butt pad.
Design and fit fore end spacer and retaining screw.
Repair ejector mechanism.
Design and fit striker and spring.
Design and fit safety detent plunger.
Assemble the trigger.
Test and return.

OK, so I kicked the job off with my own appraisal, submitted the cost of the project including costs to date (We had organised the courier to collect the gun) Sadly, at this point the customer decided against continuing with the project and suggested I kept the gun to cover my costs! Gosh I thought as I stuck the parts on the Viking’s desk and asked her to return it to the armoury, more junk cluttering the workshop up and not really even fit for spares as I could find virtually no information on the manufacturer, let alone source drawings or spares. So it was left in a dark corner as we were more than busy enough with paying work and it would never return our costs if it was repaired and put out for sale.

Many weeks later with Christmas looming and a huge backlog of gun and shiny stuff work I spotted the rifle languishing in a corner of the armoury with a label declaring it NFG (No flipping good) and to be destroyed, so I picked it up and returned to my bench with it to refresh my memory and take a closer look.

This particular rifle is badged as a PPK s.r.o, made in the Czech Republic, Model K1 and chambered in .308 Winchester. Try googling it and you are not going to find a great deal. The company is long since gone and it looks like CZ now make an updated/improved/remarkably similar rifle known as the Brno Effect however it appears to have been known as the Brno K1 prior to this which appears to be a transition rifle between the models and I even managed to discover a single page sales flyer describing the rifle range.

The rifle became an evening thing for me, just an odd few minutes before we called it a day and locked up, I was intrigued by the operation and even parts of the disassembly process were eluding me.
My tried and tested method for triggers is lay them out on the outside of the receiver, the pin holes are correctly spaced and the receiver walls are thick enough to hold everything securely. So here it is with the hammer in place then working backwards. Interestingly, the trigger adjustment is a grub screw adjusted from the top and with the main spring removed. Of course the next problem once the orientation is confirmed, is the assembly order. I initially started with the hammer however I found the correct sequence to be:

Trigger and pin and include the spring.
Cross-trigger safety.
Trigger sear.
Hammer spring rear pivot (The flat goes to the bottom)

At this point I mentally appraised all of the options for installing the hammer spring, pliers, compressors, screwdrivers were all going to be a nightmare and the actual solution is really simple. Safety off, pivot the hammer as far forward as it will go, align the spring guide and spring with the rear pivot and just cock the hammer with your fingers which compresses the spring very nicely. Now avoid pulling the trigger or you will have bits flying across the bench.

Next job was remove the top lever, this took a while to get my head around.

Push the pin circled in red out, this enables the top lever to pivot clockwise past the centre position. Now you can stuff a thin screwdriver or similar into the hole at the rear of the receiver.

(You need to remove the rear screw and butt stock bolt retaining plate first) As you push the screwdriver in you should feel the plunger compress, push it as far forward as you can and rotate the lever back and, assuming the diameter of the screwdriver is less than the plunger, you should be able to wiggle the top lever out. In turn you can remove the cocking bar and finally remove the slotted grub screw from the back end of the receiver. This one was staked with a couple of punch marks however it came out easily enough.

Now if you are lucky you will have a striker and spring that can be removed once the retaining screw is removed. Guess what, the M3 screw was missing on this one as well so that needed to be replaced. I used a High Tensile M3x20,0mm screw and will include the drawing at some point.

I seem to make a lot of firing pins/strikers, so I have a reasonable idea of what they look like so this one should be easy, well in theory it should..

First job is determine the diameter of the pin and I did this using the shanks of drill bits. I have a good range of metric drills so when I discovered a 6,0mm would not fit but a 5,80mm did as an open fit I opted for 5,90mm as a start diameter, the fun part is working out the lengths of the body and the reduced sections and this is mostly trial and error with a vernier depth gauge and bits of silver steel. With the diameters and lengths decided it was time to find a spring and luckily I had a solitary spring that seems to work. With the outer diameter of the spring now known the shoulder of the striker can be added to the drawing.

From here the length of the rear section still needs to be determined however to do that a striker pin retaining screw was needed and this took a couple of goes to get even remotely close.

You have probably noticed I do everything on CAD, it means I have nice neat drawings, I can export them as .DXF files and convert them for CNC use if needed, they are easily stored (Plus backed up!) Finally, they are very easily changed and printed out as required.
With the retaining pin and striker the next job was to start testing the parts before any changes followed by hardening and tempering, plus updating the drawings of course.

One minor issue was the ejector was stuck solid and this took some removing. It is held in place by a 2,0mm grub screw and even with the screw removed it was not coming out. A few hours sitting in some Plus-Gas and the ejector pushed out, was cleaned and is now back in and functioning correctly. It is purely mechanical and is operated by the barrel pivot and has a very simple spring plunger style thing that holds the cartridge in place when loading and unloading. I keep saying ejector however in Shotgun parlance this would be a non ejector, in fact it would be a break action single barrel non ejector, or ‘Twenty five quid’ if you were lucky according to the Viking, you can tell she is not a fan of the thing…

The stock was looking grim so I decided to take some time away from mechanical stuff to remove the finish and tidy it up. Normally a very light sanding followed by 30 minutes in the dish washer does the job but not this time. OK, some paint stripper and light scraping maybe? No chance! This took several applications of stripper and scraping plus some light sanding to get to this stage and I so with I had taken a picture before I had started.
The wood which is a very plain Walnut looks very pale which it is without any colouring or finish and I will darken it up and oil finish it as opposed to spray lacquering as it was before. Before that stage I need to chase the chequering which was probably pressure formed and is awful when you look closely. It is a very simple 20 lines per inch so easy enough to chase.

At this stage the fore end is attached in place with an M5 screw and a washer however it actually needs a plate and decent screw machining and blacking.
Well lets call this the end of part 1 even though it has been many parts so far. It is the Viking’s Christmas Day so we are going to break for food now and relax, tomorrow is my Christmas Day so I suspect it will be dogs out, food and whatever and boredom will probably set in by mid-afternoon and I will take a further look at this little rifle.
In the previous article I had got as far as machining the front half of the firing pin to confirm fit however it would need to be reduced in length and before that the safety required some attention.

The safety detent plunger was missing (Of course) This was ‘easily’ rectified with a 2,5mm ball bearing, a 2,25mm diameter by 3,5mm long compression spring and a 2,5mm by 3,5mm long cross pin. Yes, probably the biggest opportunity I have had for a real ‘Pingdammit’ in a good few weeks. For those of you that work in imperial, it was a handful of small fiddly bits.

The circled part is the pin that compresses the spring that forces the ball bearing down into a groove in the safety catch so giving a positive lock in the safe position.
Back to the trigger and ignition system. This image is the firing pin part machined/guessed laid over the receiver with the position of the hammer marked to get an idea of how the two of them interact.

The cross slot which is upside down in this image needs to be reduced to 4,0mm wide from the front edge of the existing cut (I think!) I reduced the length of the rear section to 4,0mm so less than my initial sketch and promptly assembled it forgetting to take a picture, no matter as it needs to come out to be replaced with the final item. The primer strike is OK and the protrusion has been set to an initial 1,6mm however it does not sound as crisp as I would like, so I will shorten the rear of the pin back by another 1,0mm at the back end and test again. Yes, I have a feeling the rear of the firing pin should be machined at an angle to allow for a full strike from the hammer however that is a few stages down the line yet.

With the firing pin in place, I could replace the top lever. I opted for putting the spring and plunger in place, compressing them with a suitably sized punch and sliding the lever in until the bottom diameter was holding the plunger in place, remove the punch and just push the lever all the way down.

At this stage the top lever was left of centre as the stop pin on the left hand side of the receiver was not in place, this was just a matter of hold the lever in the centre and punch the pin in with a brass drift.

At long last the rifle is assembled and ready to be dry fired. The .308 round is a dummy I have been using during the project. I have a very strict rule that no ammunition is ever out of the armoury when a firearm is being worked on or out of its slip or case. Equally all firearms entering the workshop are treated as live and checked for clear before they are fully out of the slips.

Before you ask, yes we do see loaded firearms come in on occasion and yes, I am never impressed.
Next job is to sort that front end out, it is currently held in position by a stainless M5 cap head and a couple of washers which is wrong in so many ways, so something more fitting will be machined and fitted.

To be continued…
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Author:  Alpha1 [ Thu Jan 16, 2020 8:15 pm ]
Post subject:  Re: The K1 Break action rifle (A project if ever I saw one!)

Well done. Interesting stuff.

Author:  snayperskaya [ Thu Jan 16, 2020 9:56 pm ]
Post subject:  Re: The K1 Break action rifle (A project if ever I saw one!)

Nice reminds me a lot of a Baikal IZH-18 single shot break action

Author:  Ovenpaa [ Fri Jan 17, 2020 10:47 am ]
Post subject:  Re: The K1 Break action rifle (A project if ever I saw one!)

Yes, it is quite similar to the Baikal and similar. They are not particularly popular here in the UK and having worked on it I can see why, really it was just out of curiosity that I worked on it. I must admit I am looking forward to shooting it at some point.

Author:  snayperskaya [ Fri Jan 17, 2020 6:58 pm ]
Post subject:  Re: The K1 Break action rifle (A project if ever I saw one!)

Ovenpaa wrote:
Yes, it is quite similar to the Baikal and similar. They are not particularly popular here in the UK and having worked on it I can see why, really it was just out of curiosity that I worked on it. I must admit I am looking forward to shooting it at some point.

You may enjoy it, I've shot a .308 Baikal a few times and it was quite accurate to be fair.

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