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Advisory Panel
SMLE bolt that was probably swapped into a different rifle without lapping in the recoil lugs.
“There are invisible rulers who control the destinies of millions. It is not generally realized to what extent the words and actions of our most influential public men are dictated by shrewd persons operating behind the scenes.”
Edward Bernays, 1928
Much changes, much remains the same. 
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01-27-2011 02:21 AM
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Outstanding, Surpmil! What does the other lug look like? No problems, yes? So all the load was probably absorbed by the one small lug, I reckon.
---------- Post added at 02:37 AM ---------- Previous post was at 02:33 AM ----------
Interesting dicolouration at the front. I wonder if there was already a partial failure existing when the bolt was refinished, or...?
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Advisory Panel
Originally Posted by
jmoore
Outstanding, Surpmil! What does the other lug look like? No problems, yes? So all the load was probably absorbed by the one small lug, I reckon.
---------- Post added at 02:37 AM ---------- Previous post was at 02:33 AM ----------
Interesting dicolouration at the front. I wonder if there was already a partial failure existing when the bolt was refinished, or...?
No sign of any damage to the main lug, and you'd blow the rifle apart long before you made that lug fail. I think the broken lug might in the box too, I'll see.
“There are invisible rulers who control the destinies of millions. It is not generally realized to what extent the words and actions of our most influential public men are dictated by shrewd persons operating behind the scenes.”
Edward Bernays, 1928
Much changes, much remains the same.
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I can't see the discolouration properly but the steel structure looks to me as though the discolouration is in fact part of the hardening process. Metallurgy comments JM?
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The discolouration indicates that area was exposed to either air or chemicals whilst at least partially broken. However, I won't get a reall good look until later. Computer challenged at the moment (Old PO$ monitor!)
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Using a better monitor only raises the uncertainty level! I've no idea what the discoloured area implies any more.
There seem to be small smoothed over areas at the front and, to a lesser degree, rear of the breakout. Also a colour change just forward of the lug.
There's no real sign of a slow progressive failure from what can be seen here. But...
Other things noticed:
Odd overall grey colouration of the bolt
Possible post break clean up in the lug area, or it's slightly out of focus- hard to say.
The large pit to the rear of the lug looks a lot like the sort of "spalling" oxidation found on fire damaged items, but again, nothing certain.
Other old pitting on the rear of the bolt looks like regular old corrosion.
There's a little newer rust on it, but that is to be expected!
It just LOOKS exactly how one would expect a broken lug area on a bolt ought to look! Whether or not there were multiple contributing factors, it's an excellent illustration.
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Advisory Panel
Well let me eliminate some of the guesswork: the bolt came in a box of bits, it was rather rusty and had the attention of my finest rotary wire brush, which is very fine indeed. I don't think it affected the broken area at all, other than to remove the surface rust. The wheel used lightly as I did, does not really affect colour at all in my experience, other than to show what the colours really are when the dirt and rust comes off.
There is considerable rust pitting all around the bolt just aft of the fractured area. The original finish on top of the main recoil lug/shoulder and on the bolt handle shows hardly any wear, so this was not used long and hard before failing apparently. It does look a bit like someone filed the bearing surface on the main recoil lug or shoulder however, so if that area was relieved too much, one would expect excessive loading on the lug that failed.
“There are invisible rulers who control the destinies of millions. It is not generally realized to what extent the words and actions of our most influential public men are dictated by shrewd persons operating behind the scenes.”
Edward Bernays, 1928
Much changes, much remains the same.
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Yep, I think you've hit the nail on the head there Surpmil. The whole of the recoil load was taken on the smaller locking lug. Maybe a couple of rounds before had started the fracture process then it went. A fantastic example for a class, especially during bolt fitting. A brilliant example and in the nicest sense of the word, a pleasure to see. Agreed JM? Thanks Surpmil
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Agreed! It's almost like a test piece.
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On the recommendation of other board members I would like to contribute my photos for your enjoyment.
Details as they were, rifle clean, well oiled, Remington 303 brit 174 gr, approx 25 rounds down range. Last round had a bad primer and pin went all the way through allowing some blow back of pressures.
Here is what I found inside:
PM
