Advice needed ... bolt opens on firing!

[Bruce_in_Oz]

A couple more things:

With the bolt in the rifle, the safety stud on the cocking piece should NEVER "bottom out" in the "firing side" of the cam track of the bolt. Continuous "bottoming-out" will cause a fracture of the HARDENED carbon-ally steel / "special" iron. The collar on the "mild steel" striker is where any "impact" should be taken.

SMLE strikers (should) have a qualified / indexed thread.

On drawing C-583 (13 August 1920, it states:

"30 Thds. (threads) per inch R.H.
Position and figure of thread and keeper screw recess B (ref. to drawing) to be in accordance with gauge."

Of course, one needs the spec for the gauge to establish the "start point" of said qualified thread.

On C-587 ( the drawing for the earlier (1920) cocking piece, we read:

".25 diam. 30 thds. per inch R.H. Position and figure of thread to agree with gauge.

Good luck with that!

SO, the striker and cocking piece threads are QUALIFIED and thus expected to assemble the same way EVERY time, more or less.

The cocking piece has very fine tolerances on the location of ALL working surfaces. The length of the safety stud is specified at 0.244" High and 0.240" Low. There is a 0.007" TOLERANCE on its overall position on the tongue of the cocking piece.

The length of the main parallel body of the striker is an ABSOLUTE 5.377", i.e., ZERO tolerance.

The "collar" has a 0.005" tolerance on its thickness and the tolerance for the distance from the front of the collar to the tip of the striker is 0.002", i.e. 1.368"Accept", 1.366"Reject.

No wonder these things were time-consuming and expensive to make!

And don't forget that these components were made on late-19th century machines; ONE operation (cut, grind etc) per set-up / jig, and all powered by steam-driven overhead shafts and leather belts.