Having trouble closing the action on my No4 Mk1*, need advise please.

[Peter Laidler]

Sorry if I sould a bit contrary chaps, but....... IF the bolt head is jumping out of the bolt head track on a Mk1* and the gap in the trackl guide is chipped, then there is ONLY one repair. Anything else is palliative and not a cure. Take the bull by the horns, read back on a thread where I explain the REME/Army method of repairing it, and get on with it - properly.

It's not a difficult job....., just fiddly and a good mig or tig welder should be able to repair it in minutes. There's no hardened or important surfaces near by, it ain't going to distort then all you've got to do is to undercut carefully with a fine toothed hacksaw blade.

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[Bruce_in_Oz]

Peter is spot-on.

There is a caveat or two.

IF the bolt body and/or the action body is sufficiently "flogged out", the bolt-head will "float" up and down as it is cycled back and forth.

IF, furthermore, the bolt head lacks the tiny chamfers on the "rib", it is very likely that the guide-rail on the body will start to suffer chips rather quickly. I understand that this "chamfering" of bolt-head "ribs" started in Canada sometime in the late 1940's.

Another factor, closely tied in with the "looseness" of the bolt is the effect of a fully/mostly filled magazine has on the "tilt" of the "loose" bolt body. I have long harboured a suspicion that some of this damage can be sheeted home to "dry cycling" as there is almost ZERO vertical pressure applied to the bolt body by an empty magazine. Ditto the "style" of the operator's working of the bolt. Note that as you retract the bolt you are applying an upwards force on the bolt handle. This in turn depresses the front of the bolt. When that happens, the bolt head lug will rotate with the inner edge of that flat guide surface acting as a fulcrum. That MAY explain why the corner at the REAR of the gap seems to suffer the greater damage.

Or am I barking up the wrong tree here?

[cthulhudarren]

Sorry if I sould a bit contrary chaps, but....... IF the bolt head is jumping out of the bolt head track on a Mk1* and the gap in the trackl guide is chipped, then there is ONLY one repair. Anything else is palliative and not a cure. Take the bull by the horns, read back on a thread where I explain the REME/Army method of repairing it, and get on with it - properly.

It's not a difficult job....., just fiddly and a good mig or tig welder should be able to repair it in minutes. There's no hardened or important surfaces near by, it ain't going to distort then all you've got to do is to undercut carefully with a fine toothed hacksaw blade.

Thanks Peter, I am very interested in this article! Would I find it in your link of indexed articles? I could not find such a post in your links or searching the forum. Would you know more specifically I could use as a search term?

---------- Post added at 08:57 AM ---------- Previous post was at 08:53 AM ----------

Peter is spot-on.

There is a caveat or two.

IF the bolt body and/or the action body is sufficiently "flogged out", the bolt-head will "float" up and down as it is cycled back and forth.

IF, furthermore, the bolt head lacks the tiny chamfers on the "rib", it is very likely that the guide-rail on the body will start to suffer chips rather quickly. I understand that this "chamfering" of bolt-head "ribs" started in Canada sometime in the late 1940's.

Another factor, closely tied in with the "looseness" of the bolt is the effect of a fully/mostly filled magazine has on the "tilt" of the "loose" bolt body. I have long harboured a suspicion that some of this damage can be sheeted home to "dry cycling" as there is almost ZERO vertical pressure applied to the bolt body by an empty magazine. Ditto the "style" of the operator's working of the bolt. Note that as you retract the bolt you are applying an upwards force on the bolt handle. This in turn depresses the front of the bolt. When that happens, the bolt head lug will rotate with the inner edge of that flat guide surface acting as a fulcrum. That MAY explain why the corner at the REAR of the gap seems to suffer the greater damage.

Or am I barking up the wrong tree here?

This seems to have merit. In my original thread I stated that if there are cartridges in the rifle then the frequency of this happening drops to about 1 in 4.

---------- Post added at 09:02 AM ---------- Previous post was at 08:57 AM ----------

IMO this one part of the Mk1* "design" that is an Achilles heel. I know it was a wartime expedient but I think the No4 Mk1 is a better rifle. The caveat being that I am not an expert, just a fan.

---------- Post added at 09:06 AM ---------- Previous post was at 09:02 AM ----------

My particular rifle was lightly used, the barrel is in excellent shape with no detectable wear. This damage probably came about from too much cycling of the action in an empty rifle. I am also going to look into the angle of the cocker spring binding up inside the bolt and causing the bolt to want to turn.