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

[cthulhudarren]

I apologize in advance if I butcher the nomenclature...

I have been having trouble getting the action to completely close up on my No4 mk1*. What I observe is that the bolt head, riding along the groove in the action of the receiver, turns slightly to the left when it gets to the section of the receiver "rail" near the front of the receiver where you can take the bolt head out of the action groove. This is also the point where cock-on-close process begins compressing the firing pin spring in the bolt.

So as you are pushing the bolt forward, when the bolt head gets to the place where there is a gap in the rail/groove, the bolt head turns slightly to the left and gets out of alignment with the action groove in the receiver. Then the forward travel gets hung up right where the bolt head should re-enter the action groove. You can see the groove in the bolt head is hitting against the groove rail of the receiver because they are slightly out of alignment.

This seems to happen 90% of the time when you are cycling the action with no cartridges in the rifle. If there are cartridges in the rifle, it only fails to close about 25% of the time. If I work the action, keeping the pressure on the bolt head with my finger to keep the bolt head turned fully to the right and in alignment with the action groove, it closes every time.

Any advise on this? What would cause the bolt head to turn? Could it be the firing pin spring causing the bolt head to turn, it seems like it is possible.

Thanks in advance

PS I have made sure that there aren't any burrs on the bolt head or the receiver groove rail causing this.

Information

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[CODFan]

Remove the Bolt.

Turn the bolt head to the left as far as you can (orientation as if you are Looking forward towards the action)

Does The bolt head should turn 20deg past "straight"?

Ensure the bolt is properly seated when reinstalled.

Please report back and let us know.

Hope this helps.

[cthulhudarren]

Remove the Bolt.

Turn the bolt head to the left as far as you can (orientation as if you are Looking forward towards the action)

Does The bolt head should turn 20deg past "straight"?

Ensure the bolt is properly seated when reinstalled.

Please report back and let us know.

Hope this helps.

No it does not. Maybe 10 degrees at most.

[browningautorifle]

Sounds like there may be a problem with the track itself, as in a chunk missing. Can you take a pic of the track? This is a Long Branch rifle?

[cthulhudarren]

Sounds like there may be a problem with the track itself, as in a chunk missing. Can you take a pic of the track? This is a Long Branch rifle?

There are small "chunks" missing from the corners of the tracks where the tracks begin and end, but I thought they might be normal or just slightly worn? The bolt head itself is turning when the spring compression starts inside the bolt. Any chunks missing in the rail look to be from the bolt head groove slot hitting it due to being slightly out of alignment. Are there any closeups of a Mk1* rail groove that I can see that show what it should look like?

[cthulhudarren]

FYI, the bolt head is a "0" and the rifle head spaces and shoots very well. The rifle is in very nice shape with very little wear. I did find a few shots of mk1* groove cuts, all were in better shape than mine. Some I could see also had some rounding off of the corners of those places where the gap begins.

[browningautorifle]

The firing pin no longer bears against the bolt head when the firing pin is being withdrawn. The chunks are not normally missing but it used to happen. There are threads here pertaining to it. It should be a square corner and if yours is way worse than it should be, the only way we can see is to see yours. The reason it's happening sounds to be because of the bolt track being damaged.

[Parashooter]

Restoring a worn bolt-head rail is a rather delicate welding and shaping job not easily performed by most amateur or general gunsmiths. There are however, some "field expedient" remedies that can prove helpful and require less specialized skill and tooling.

1. The slot in the bolt head can be chamfered to encourage the head to remain on track during operation.
2. Worn/chipped portions of the rail can be carefully peened inward far enough to engage the bolt head slot (a bit).
3. Heavy/sticky grease applied to the bolt head threads will help prevent the head from rotating during that part of the cycle when it should remain in place.

[Thunderbox]

As stated, sticky grease on the bolt head threads often cures this.

Is the bolt numbered to the rifle? If not, might be worth trying a different bolt and/or bolt head. This also quite often cures this problem completely - Enfields are a bit organic/individualistic, and its often a mystery why one component works and another does not...

[cthulhudarren]

Nope, bolt does not match, it is close but no cigar. The rifle is a Savage, BTW.