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This is one for any CZ527 owners, preferably chambered in .223Rem. I would like to know what the core diameter of the bolt is please, I have it as 14,8mm however apparently this might not be the case.

Hi Dave.

I have a CZ527 in .223, it is the kevlar varmint version. I will not be able to take measurements until tomorrow or Sunday at earliest, so if it's urgent I'd suggest someone else help out.

Are there any other measurements you'd like while I'm at it? Feel free to annotate a picture. I have a micrometer and a set of calipers.

I am happy to wait as I will not start the job until next week, it is just the diameter of the bolt I need however it would be good to know how the bolt release works as I have just had a guide returned as not fitting and I have built a few in the past without issues.

The bolt release is controlled on the left side of the receiver just like a Tikka. The latch is a thin metal plate which slides into the bolt. My universal cleaning rod guide does not fit, and this latch can scratch the cleaning rod if you're not careful. I use a miniature G-clamp to hold the bolt release down when I clean my rifle.

I can take a few pictures and a video over the weekend if that would be of use to you?

A picture or two would be handy if you have time. Does this mean if the bolt release is not fully depressed the guide cannot be inserter? It sounds like a slot or locking groove would be in order.

Yes, it's a spring loaded latch which you must apply force to keep open. However, you could slide a guide in without holding the latch open but I imagine that the latch would wear the guide (or vice versa depending on the material you make the guides with).

Thinking about it... The latch also acts as the ejector. The first picture shows the narrow, milled slot where the ejector resides to eject a case. The second picture shows the ejector with the bolt removed. When you hold the bolt release button on the side of the rifle, the ejector moves flush with the receiver such that you can remove the bolt or insert a bore guide without the ejector rubbing against it. Hence the use of the G-clamp I discussed.

So when the latch is fully depressed with the bolt out the ejector stop will still be extended and does not compress until it has been guided through the slot in the bolt and cams/pushes out of way by the closing of the bolt?

No, when you fully depress the bolt release the ejector moves out of the way, the receiver will be completely unobstructed when the bolt release is held down.

Hi David. Here's a summary of the measurements I took. See the crude drawing of the bolt along with the sections where I took a measurements. I rotated 120 degrees and took measurements at each point. I used both a micrometer and a calipre. The maximum diameter of the bolt body was 14.95mm on my bolt.

After the measurement pictures, I included some images and a video showing the bolt release.

Let me know if you want more pictures, videos or measurements of the bolt, I am happy to help.





Zero-ing of both devices



Maximum measurement readout on the micrometer



The first set of pictures show the bolt release untouched (i.e. normal). You can see that the extractor is in the way, should you insert a bore guide down the bolt runway. The second set of pictures show the extractor when the bolt release is depressed. Notice that the ejector does not go fully flush with the receiver. A bore guide of diameter 14.95mm or less should be able to slide down the bolt runway.

Bolt release untouched



Bolt release depressed

My 527 (.223) bolt measures 14.88 - 14.91