Zermatt RimX headspace

[Will Henry]

Then notch the boss to clear the plate. I have not looked at this action, but I assume the extractor does not rotate. The alternative would be to thin the plate by .005 or so. I'm beginning to think that shortening the bolt to reduce counterbore depth might be the way to go (Thin the plate at the same time). A disclaimer here: It's not my action! WH

 

[Will Henry]

Having seen the picture, I would not thin the extractor plate. It's barely there already. In fact, I would be inclined to make a thicker plate and cut a notch for clearance. I can see now why they made the countbore a little deep. It's just to accommodate the extractor design. If I was building this action, I would reduce the length of the bolt nose and plan on making a cut for the extractor, which I would make a little thicker. Again, I'm just an old 'smith and not an action designer or builder. WH

 

[jelrod1]

The original design is the way it is to accommodate prefit barrels. This is what I do to them in my ModX conversions. It obviously requires extractor cuts.

 

[Judd]

Doug…I’m glad this is your project and not mine. I thought I knew what was up when I saw CigarCop’s picture but I’m more confused than when you started now.

 

[padom]

OP, your thinking is correct for all previous precision Rimfires up until the RimX was released.

In the past, we would cut headspace based on ammo used.. less headspace (0.038-0.039) for Eley with their thinner rims and more headspace (0.041-0.043) for Lapua with their thicker rims.... This was done for optimal ignition, so the round didnt move forward when struck by the firing pin or so rims werent crushed... This provided consistent, optimal ignition for the ammo being used in the specific rifle...

With the RimX, that is out the window and doesnt apply.. The RimX was released with a brand new design that didnt exist to my knowledge previously. The round is captured against the bolt face when its stripped off the mag and held against the bolt face the entire time via the extractor and tensioner. It cannot move forward once its slid up the bolt face or struck by the firing pin..

Because of this, headspace doesnt matter because you dont have to worry about the round moving forward when struck.. Now you just pick your preferred reamer, set your amount of engraving and your good to go.

I was sent one of the very first RimX's by Zermatt (Serial #005) before its release for testing. It was hard to wrap my head around this new design and headspace not mattering because of how we have always cut rimfire barrels... I was assured this no longer applied by Zermatt.

We cut the barrels to Zermatt's minimum 0.0465 headspace and got to testing. Now with 40+ barrels tested on my RimX and well over 50k rounds tested, this design has put out amazing accuracy.

I know guys like @jelrod1 have been modifying RimX to go back to the old extractor style rimfire rifle where at that point you do now have to set headspace based off ammo your shooting and time and cut extractor grooves and I understand why this is being done. When you get a round in front of the bolt and stuck in the chamber during a stage in a match it can be detrimental and some people want that peace of mind.

I personally dont have this issue. I believe a large part of this is which stock/chassis you go with and proper mag setup. My RimX has been in an XLR Envy Pro since day 1 and it feeds and extracts like butter without any issues.. I know a lot of people had these issues where the round wasnt properly slid up the bolt face and fully captured behind the tensioner and extractor and then gets pushed into the chamber int front of the extractor and then gets stuck. Only way to get it out is with a cleaning rod or a knife to pry it out.