Bolt head jumping track, wot, again? yup, fraid so

[tbonesmith]

I had the same problem on a '42 or '43 Lithgow range rifle, it did it with every bolt head I tried. I parted it out, the best part about it was the barrel anyway.

[newcastle]

So on these rifles. What is the danger of the bolt head jumping the track? is it safe to fire when the bolt head is properly engaged? the reason I ask is because I fired this Lithgow several times before I noticed this.
As far as I can see, if the head had moved up then the rifle will not load - correct? and as the rifle is "cock on closing" if it is not sliding into battery then the firing pin will not be cocked, and therefore there is zero risk of firing before the locking lugs have engaged and the bullet is properly seated? The biggest danger would be for instance if a german / japanese / north korean (insert as appropriate) was charging you with a fixed bayonet and the bolt head coming off the rail meant you could not fire the rifle. Am I wrong here?

[Peter Laidler]

If the bolt head of the No1 or the No4 jumped out of the bolthead track while on its way forwards, then according to my skeleton action, the extractor would stub itself onto rear face of the barrel or onto the rear surface of the breeching up ring because being rotated slightly anti-clockwise, the extractor would miss the extractor slot. The breech wouldn't lock and the imbuilt mechanical safety would come into play

If I was facing any of the foes you mentiuon, I'd be rummaging around in my small pack for some toilet paper

[newcastle]

So in other words, toilet paper requirments aside. The bolt head rotation means that it CANNOT be fired in this situation and therefore when the bolt head is IN place it should be safe to fire (notwithstanding headspace , locking lugs and all the other stuff which needs to be in spec to have a safe Lee Enfield)

[Bruce_in_Oz]

Bolt alignment is one of the few weaknesses in the Lee Enfield design as I see it.

The problem stems from the fact that there is very little to stop the bolt from floating up and down because the top and bottom of the raceway are cut away to allow passage of the locking lugs.

If you carefully watch as a bolt is being manipulated during firing, you will notice the following (tendencies):

As the bolt is withdrawn in the extraction/ejection stroke, most of the time you will see that the firer's hand causes it to tilt up at the rear.

Conversely, during the feed/chambering stroke, the operators hand tends to cause the rear of the bolt to tilt downwards.

This "see-sawing" has the effect of wearing the bolt body and the receiver in such a way that the problem can only get worse.

This vertical excursion thus also has an effect on the retaining nib of the bolthead, be it No 1 or no 4, because it too will rock up and down.

On a No4 Mk1 or 2, with their continuous track, things have to get really flogged out before anything nasty happens. However, on the 1*, it doesn't take much wear to cause the bolt head to float around to the point where it will start to collide with the edges of the cutout in the rib on the receiver. One this starts to cause chipping, you are in real trouble unless you get a new bolt assembly AND can find someone who is good with a TIG welder and miniature grinders.

Another thing to note is that the vertical excursion of the bolt running over an empty magazine is quite different in nature from its behaviour when handling live or drill ammo.

Over the years I have noticed that many Mk1* rifles have little bevels on the upper surfaces of the end of the nib of the bolt head. This actually helps greatly to reduce damage to the receiver. However, I have yet to find documentary evidence of the origins and official (or otherwise) stature of this modification, even in the few Canadian workshop documents that I have seen.

Wear at the rear of the receiver also causes the SMLE bolt to float about. Couple that with wear or damage to the receiver rail and bolt head, and things start to get annoying.

One has to constantly keep in mind that these rifles were not exactly made yesterday, nor have they always been meticulously maintained, especially since they left their original service.

[lngstrt]

I de-sporterized a 1940 Ishy last year that had/has this issue. With any upward pressure from 2nd etc. rounds in the magazine and the bolt head jumps the rail. If I go slow and hold the head down it's fine. Now, workin an Enfield bolt slowly is no fun, but, shooting over a bench at paper I can barely see .... it's fine. My Dad has had this rifle since the 70's and never fired it. I just had to make it look like a battle rifle again and .... then I found the track jumpin problem. Oh well, she looks like she's supposed to now.

[Peter Laidler]

We regularly repaired hundreds of Mk1* and 1/3 rifles with chipped bolt head slots. It was quite easy and I detail the repair elsewhere if anyones interested.

Like Bruce in Oz, I have noticed the little chamfer on the undercut of some bolt heads and again, I can find no mention of it in any official documentation, especialkly in our EMER bible. On the point you make about the up and down rocking movement of a bolt being moved forwards B in O, this is almost academic in practice because onvce the bolt actually locks up it will centralise itself against the even locking lugs and sit absolutely squarely against the round in the chamber. Any forumer wanting to test this, just blue the rear of the reject CHS gauge, slide it into the chamber and slowly close the extractor-less bolt and bolt head on it. You will (?) have the perfect circle of the gauge marked on the bolt head face. In any case, a badly worn body that exhibited exaggerated bolt rock would have been picked up by the Inspectors calibrated bolt. Loose and the rifle was in for the chop!