Cocking piece fouling

[PrinzEugen]

Hello - I have a no4 of which the cocking piece is fouling on the right side when engaging (?) during the cocking action. It cocks ok but clearly it would be good to remedy this in hopefully a simple (!) way. Any help much appreciated.
When entering the square groove of the receiver it hits the right side of the groove.

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[Son]

Hello - a friend of mine has a no4 of which the cocking piece is fouling on the right side when engaging (?) during the cocking action. It cocks ok but clearly it would be good to remedy this in hopefully a simple (!) way. Any help much appreciated.
When entering the square groove of the receiver it hits the right side of the groove.

Hmmm, could be a couple of things. Check the cam grooves in the bottom of the bolt body for damage or bulid-up of crud. Also check the corresponding camstud above and just back along the cocking piece from the bent.

If the bolt is allowed to over rotate on opening , then it would cause this also... but that would mean the sides of the locking lugs were seriously worn down....
just thinking out loud now... something is definately not right.... or have I missed something...?

[Peter Laidler]

It sounds like the striker spring to me. The spring should be in a mechanically neutral position when in the bolt. That is slightly compressed but not over or under wound so that it will cause the striker (and therefore the cocking piece) to twist to the right and engage the side of the body. If it IS UNDERWOUND, it'll have the effect of unscrewing the cocking piece which when the bolt is being pushed forwards, the stud of the cocking piece SHOULD be sat slap bang in the centre of the short cam groove of the bolt.

The cut-off ends of the striker spring can get caught up on any rough edges deep in the shoulder of the bolt and also on the underside of the striker, where it's recessed for the TOOL, removing striker.

But I feel that it's not this and am inclined to agree with fellow Armourer Son in many ways.

Make sure that it's not canting over to the right as it engages with the sear. If it does this, it means that either the sear nose or the face of the cocking piece is not square.

There's a bit of heavy Sunday morning reading for you!

[Son]

Just thinking again- I'm going to go with the crud or burrs in the bottom of the short cam groove at the back of the bolt body, probably because it's the easiest problem to check out. If you need to fix it, or it isn't the problem then a bolt strip is on the agenda. It would pay to check the spring surfaces as Peter suggests while it's apart. I wouldn't have thought of that as the problem, not before tearing my hair out anyway Peter.

Here's a pic of a No1 cutaway I just borrowed. Similar enough to get the idea...
Where the purple dot is shows the long cam groove. The cam stud on the cocking piece goes from the bottom of the long groove to the bottom of the short groove when the bolt handle is lifted to open. This action cams the cocking piece back withdrawing the firing pin from it's hole in the boltface. You need to check the cam grooves for damage or foreign material and check the shape of the cam stud on the cocking piece also. If the front edge of the stud is damaged, it may not be locating in the right spot in the groove and not aligning with the receiver when closing the bolt.

[PrinzEugen]

Thanks chaps - I'm going to take it over to another chum who is reasonably good with guns and stripping bolts and so on when I get the chance. Thanks a lot for the tips - it's invaluable to know what to look for!

[Peter Laidler]

Hey Prinz, you ought to tell your pal that you're going to see that you couldn't get any sense out of the thickies on the forum so you worked it all out by yourself. Even the REME/RAEME Armourers were rubbish......! Have him on a bit but let us know what the problem was.

[PrinzEugen]

Ha! If I claimed any technical knowledge I think he would certainly know it hadn't come from my little grey cells!
Oh and special thanks to Son for the diagram - very useful - I would only have been guessing which bit was which cam!

I'll let you know if we work it out - although it'll be a little while before it happens.

[Bruce_in_Oz]

Hi, Prinz.

A couple of things to check:

Does the cocking piece bear on the side of the slot in the receiver before engaging the sear?

If so, there are several possible explanations. 1. The bolt lugs are unbelievably worn. 2. The receiver is unbelievably worn. 3. The cam track at the rear of the bolt is damaged or dirty. 4. The safety stud on the cocking piece is missing, incorrectly located or damaged.

If the cocking piece appears to be centrally aligned before contact with the sear:

The full bent (nose) of the cocking piece has been butchered by someone trying to adjust the trigger pull. 2. Ditto for the sear. 3. Could be both components are faulty. Note: If too much material is removed from either component, the driving flat on the safety lever will not engage the front notch in the LHS of the cocking piece correctly and will get chewed up. Cocking pieces are differentially hardened; the front end is seriously hard, whilst the rear is reasonably malleable. (Sorry, tech docs not to hand at present)

Peter Laidler's point about the spring is very important. If the closed and ground ends of the striker spring are roughly finished, they will bind on any surface imperfection on the rear of the striker collar or inside the rear of the bolt body. One addition to this is burrs and "dags" on that rear of the striker collar caused by striker tools with damaged or incorrectly manufactured driving lugs. If the bolt handle flips up when dry-fired, spring torque is one of the causes.

[PrinzEugen]

Thanks for that Bruce - yes it does flip up somewhat on dry firing - what's the remedy if it is the spring? - a new one?

[Peter Laidler]

If yoou need a new striker spring, just ask