· British 303 are head spaced on the rim – really a rim space, which is changed by changing the bolt head for one with a different (target) length – the rifle action is “failed cartridge safe” by design – the rim space limits are very generous by design and manufacture (with war time relaxations) to allow all grades of ammunition to chamber under all conditions. Tightening and "over head spacing" (rim spacing) is probable and this challenges the bolt achieving “lock”.
· Bolt heads were rough graded into size groups before finishing – these were overlapping for actual size and were a quick reference. Plotted below are my inventory notes from having sold over 200 No4 Rifle bolt heads - plotted by actual head length, indicated reference "size" and the factory that made them. You can achieve the same target length with bolt heads size marked as "0, 1 and 2" - such as the 0.633 example. This also indicates what I have experienced in the market obtaining certain sizes by maker - Ill keep my eye out for more and add them.
· Bolt heads from Savage and Long Branch were prepared for use in the No4mk1* rifle bodies by adding chamfers to the rail groove edges of the bolt head – this prevented the rifle body rail groove being chipped and making the rifle body unserviceable on this model which was simplified with the bolt head release deletion.
These chamfered bolt heads are interchangeable with other makes and models, but a No4mk1* or the rebuilt No4Mk1/3 models will need a bolt head with the rail groove chamfers.
Armorers would allow a rifle to pass with a size 2 bolt head fitted if it passed headspace. Instead of working up to a size 3 – they would change the bolt body to go back to unworn lugs and retain a size 2 max bolt head. Size 3 bolt heads were held in stock and rarely issued – they appeal to the north American after-market users – see points above.. I have observed one rifle with a No3 bolt head fitted - the bolt handle serial number had a "A" suffice - which indicated a non standard part. The rifle serial number did not have this suffix though.
· Another North American myth is that all Lee Enfield's have bad headspace as surplused and this can be tightened by turning the bolt head a whole turn. This puts excess pressure on the lugs and can shear them – if it allows the bolt to close at all – the bolt head is unsupported and misaligned. I’ve seen several rifles at shows in this “bolt head turned out” condition – I have also been asked to replace bolt bodies with the short bolt lug shorn off.
· Bolt assemblies were dedicated and serialized to the rifle – because of the variation of the fore end, trigger guard and the trigger on the sear – they were all hand fitted in the following sequence:
Bolt body locking lugs to have equal lock up and contact with body lugs (tested with engineering blue).
Cocking piece bent to be flat and square and engage with the sear in the rifle, cocking piece to firmly grip the striker when fully screwed in.
Bolt head to slightly overturn the long rib when screwed home. Bolt head to slightly “lift” the cocking piece when screwed home.
Striker to produce required force, have required shape and protrusion when in the “fired” groove.
It is these relationships that require the rifle to be present for assembling the bolt and to have many choices of bolt heads to get the right fits – other fits and functions can be linished or finished to work if it is a "material off" condition. Beware of ready assembled off the shelf bolts - you may get lucky - or otherwise.
· There is a lug between the two grooves in the bolt body for the cocking piece guide – this prevents the striker going forward when the bolt is being locked in place – these lugs (between the bolt body grooves) can be sheared off and should be checked as intact and functional.
· On the cocking piece there are two grooves as well as the bent – each one defines one position for the cocking piece (and attached striker) – full cock, half cock and fired. A rifle can have the cocking piece pulled out to the first (half cock) notch – this will lock the bolt in place if done when closed – to remove it from half cock lock – pull the cocking piece back to the second full cock position.
· The winding of the striker spring is left hand and when such a spring is compressed (like when the rifle is cocked) the spring develops a torsion reaction in the opposite direction to its winding and expands to run the inner bolt body surfaces (all springs do this when compressed). When this torsion is released (firing the rifle), the result is a secondary reaction turning force that can (on some rifles) unlock the bolt (turn it up) after firing (firing being instantaneous – the bullet is long gone before the bolt turns up). It is normal on a well set up Lee Enfield to see this – but it can still be disconcerting.