Is this a common failure?

[Bruce_in_Oz]

I have seen a few of those fractured cocking pieces over the years. Oddly enough, by far the majority were for No 4s

On each occasion, it was obvious that the crystal structure at the point of failure was extremely large for such a tiny part.

Accoring to my notes about the manufacture of the cocking piece, it was meant to be differentially hardened; i.e., the front bit with the bents and locking bolt notches was supposed to be very hard, and the rear section, with the thread for the striker, was meant to be "tough" but not hard.

Look at the early pattern No4 cocking pieces. Notice the "step" at the junction between the rear section and the tongue with the bents etc in it. That was there to eliminate (hopefully), stress risers that would form if there were a sharpish corner there. Expensive and fiddly to make, as is the SMLE type.

When these parts were being made, three shifts per day by emergency sub-contractors, things were bound to go amiss fron time to time.

Furthermore, the only steels used were high-carbon types that require quite careful handling when hardening.

There were no pyrometers, infra-red thermometers etc in those days. When the instruction said "heat to chery red and hold X minutes and then quench", things were bound to get a bit variable.

Too long in the furnace or too high a temperature and the crystal structure was a risk.

"Cherry Red" is a nice description, but what does it mean? And "cherry red" in what ambient light; the morning shift or the gravehard shift?

Add to that the fact that carbon steels "age" over the years and the crystal structure can become brittle over the decades.

Side-note:

The components of the AIA rifles are made from modern European and American sourced alloy steels. It will be interesting to see what happens to them over the next sixty or so years.

[Peter Laidler]

Ooooooooooooo, JM, Have you still retained the small cam groove stud? If not, you have just eliminated one of the most important mechanical safeties of the No4 rifle there. You can fire the rifle with the breech not fully closed. Not my idea of a good idea......................

Just bear this in mind if you do try it lads.

I know what soeones going to add.............. That the No8 hasn't got this feature! I know, but mechanically, it doesn't work like the No4, it's a different beast.

[Bruce_in_Oz]

Excellent point, Peter.

I'll chuck in my two-bobs worth here.

Over the years I have encountered several SMLE range rifle here in Oz, that had the cam groove stud missing, not from the cocking piece, but from the bolt body.

Allegedly, this was done deliberately to "improve" bolt closure or some such. In several cases, it was obvious that some individual had adjusted the full-bent "nose" of the cocking piece by shortening it and altering the vertical angle: BOTH adjustments are serious errors in terms of safety and function. Sometimes the tail of the sear had been "worked on" as well.

Many full-bore shooters in the last years of the SMLE even removed the safety catch assembly. The rationale was that, snce the elimination of military-style snap and rapid matches, and the imposition of "single-loading" rules, there was no point in having a safety catch. Bizarre!!.

Once you fiddle with the length of the sear and cocking piece full-bent, the stud on the bolt body no longer does its little dance around its partner on the cocking piece: they crash into each other and things get untidy. Bubba solution: knock off the stud!! Never mind that your rifle WILL now fire with the bolt somewhat less than fully locked.

Note also that in earlier days, the initial striker for the SMLE had a small square stud on the forward face of the collar. This serves two purposes; firstly, give the striker tool something to drive against and secondly, line up with a square notch in the rear of the bolthead thread.

Somewhere along the line in WW1, this feature was dropped (hence striker "B") and only the studs in the bolt cam groove and on the cocking piece remained.

The studs act to prevent the striker reaching a primer unless the bolt is (more or less) fully closed. Try this experiment (with a VERY unloaded rifle):-

With the bolt closed, draw the cocking piece fully to the rear. Raise the bolt handle 10 degrees or so. Pull the trigger. The bolt handle should snap closed quite forcefully. This is because the radiused ends on the two studs acted to cam the bolt closed. If you were silly enough to try this with a primed case, it may not have ignited, as the speed of the striker has been reduced by this mechanical interaction. Then again, if it did fire, at least the action was fully locked at the time.

Repeat this exercise with the bolt handle raised further. Very quickly, you will notice that the studs collide quite audibly and the bolt handle will again be driven to the closed position. What also will probably happen is that the cocking piece will stop at the half-cock notch. This is the other cool feature; the action locks, and you still have your face. Pull to full cock and carry on.

Once more, with feeling; do NOT fiddle with the controlling surfaces on the bolt or cocking piece. If you lose the correct relationship you will not only "bugger up" the free movent of the bolt, but render the locking bolt/safety catch inoperative.

[Peter Laidler]

Wise words Bruce. And anyone out there in forumland, ignore them at your peril................. Look up a previous thread about how to set up your bolt perfectly. There is really only one way and that's the right way

[jmoore]

Ooooooooooooo, JM, Have you still retained the small cam groove stud? If not, you have just eliminated one of the most important mechanical safeties of the No4 rifle there. You can fire the rifle with the breech not fully closed. Not my idea of a good idea......................

Just bear this in mind if you do try it lads.

I know what soeones going to add.............. That the No8 hasn't got this feature! I know, but mechanically, it doesn't work like the No4, it's a different beast.

Sure, the stud's still there! No worries.

[jmoore]

Whilst on the subject of parts failures, I have seen sheared off cocking studs as well, but if you've an EDM or carbide drill bit, I reckon that is "fixable" by installing a pressed in hardened pin. In most cases it seems hardly worth the bother. Just replace the cocking piece.

Another rather more dramatic failure is the loss of the small lug in the bolt's cam channel raceways. Basically makes the bolt a write-off, AFAK. It doesn't seem all that big a deal, but it plays hob w/ reliable function. I've two or three bolts "somewhere" that have broken in this manner.

ETA: More mayhem in a new thread.
Link below:

https://www.milsurps.com/showthread.php?t=27425&p=151089

"Gallery of Dramas. Broken Enfield Parts!"