Bolt Head Fitment

[xa-coupe]

If you remember I had an issue with the extractor on my no4 7.62. Rather than actually perform any manual work I swapped the whole head out for another one I have handy.
The bolt head screwed on alright but as I got it to the end, rather than over rotating it barely screwed in enough to line up with the locking lug. In fact, I had to exert considerable force ( only by hand ) to get it to line up. Once I put it in the rifle it took considerable force to twist the bolt head around to put lock it in. Once it's altogether it is fine and appears to operate perfectly.
The old bolt head was ~625 in and the new one ~632 in. I don't know that this has any real relevance other than the headspace is now less.
The bolt head is used but I have never had to use so much force as usually they over rotate, not under rotate. Has anyone else had this?

Information

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[tbonesmith]

I've seen it a few time when I went to change boltheads. I think it's normal and you just need to pick one that will index right.

[xa-coupe]

Thanks TBone.... I think it will index okay after a bit of use but I haven't have one this tight before.. usually they are at the point when I am wondering whether to change it because it's too lose !

[Son]

For the No1 rifle there was a tool for working the thread until it indexed. I don't know about the No4...

[xa-coupe]

Thanks Son, I will just perservere and wind in up tight and undo it. I should check the headspace before I get too excited as it may be too tight and I am wasting my time.

[Peter Laidler]

You could gently stone a gnats knacker from the front face of the bolt but be sure that it is only a gnats knacker and NO more. What you have is mechanically perfect alignment and the load of recoil will be taken through the bolt head directly onto the face of the bolt and backwards as opposed to on to the threads and downwards.

This was VERY common when you were doing hundreds of them. But now you've fitted the new bolt head, are you sure that the FPP is correct? Are you sure that the lift is correct? And what about the CHS - apart from the assumption that it's '..... a bit less'. If it was actually .068 before, then you deducting .007" makes it .061...........

Think again XA!

Don't forget also, that what you have done hasn't actually told you what was wrong with the old bolt head or extractor or spring or combinations of each

[xa-coupe]

Thanks Peter.. fear not, It won't be fired until I check a few things .. such as CHS ! It was just a thought at the time to make sure that the bolt would close and I hadn;t stuffed something up. I was not expecting to have it so tight. For the moment I won't be removing knackers, gnats or otherwise, until I can chack the headspace. If it is too tight then I won't be altering the bolt head at all. The old head was .625, the .632 was only because that's the only spare bolt head I have, not because I think it is correct. Without a CHS guage it's just guess work.
I am confdent the the extractor cutout in the barrel is only machined for a 303 style extractor amd the slightly beefier 7.62 extractor just hits the metal. When I have some $ I will get someone here with more knowledge than me to check that I am right and then fix it. In the mean time I need to find the extractor I took off the original bolt head and put it back on.