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I think part of the problem when examining these rifles after many years of commercial (private) ownership is we have no idea the misuse the parts have seen. A bolt head could have been swapped for tighter headspace but not properly fitted. I've actually seen guys take an OA torch to a cocking piece to "slightly soften it" so they could cut it with a file while "match tuning" their "deer gun". Things like this make failures both more likely and more difficult to attribute.
Ahhh, the oxy torch. Here's a couple of pics of the sort of things you'd be talking about- except these "mods" hadn't failed at this point...Quote:
Originally Posted by Claven2
LOL - 4 (count them) FOUR(!) D&T's to that one poor bridge... lol.
Is it my imagination or have you found pictures of two of the rarest firearms about? The vintage left handed smle and the left handed swede .. only issued to left handed commandos for the raids on left handed germans ?
What annoys me is these guys are obviously military rifle club types and should know better. The only saving grace is if they were non matching. Even so ......
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Originally Posted by Claven2
So far, all of the broken cocking pieces and bolt head(s -I've more!) were in a large lot of pre-1968 import weapons that never left the retailer's floor until the owner died some 20-odd years later. Obviously, what he hadn't sold were the worst of the lot! So, it's likely this stuff is more or less the "floor sweepings" of an armory that got crated up and sold in bulk. This surplus dealer bought mountains of equipment back in the day, and had a 10m square room full (meaning "piled up") of Enfields still in the late 1980s!
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Originally Posted by Claven2
Something that came up in one of Spinecracker's threads may help explain part of the reason beyond those already listed: Inspection stamp impressions located in the stressed area! The localized deformation is a perfect nucleus for "fatigue failure" in an area that wouldn't otherwise be expected to see large cyclical loads. Little things can make a huge difference!
Link to Spinecracker's thread below, ref. Posts #53 through #58- possibly more.:
https://www.milsurps.com/showthread.php?t=21764&page=6
"New '41 Long Branch..."
Railroad bogeys (wheels, specifically) were one of the first well investigated items where tiny inspection stamps in the web led to catastrophic failures (and some derailments!) long into their service lives. I know that Glock Inc. moved the location of their slide proof marks away from the ejection port for the same reason. (I may have even been the one that first recognized the problem, but I can't verify that suspicion- Austria wasn't very forthcoming at the time when dealing with new dramas.)
Other "crack starters" that spring to mind that don't lead to immediate failures: Machining marks, heat treatment micro cracks, Chrome plating, random scratches, corrosion pits...Aside from the Chrome, many of these features can be very small!
Regarding SMLE cocking pieces:
From: Specification S.A. 462 P, Dated 14 December 1938 -
"22. Cocking-piece, "B". - Will be gauged for width and figure, position and diameter of keeper screw recess, threads, and position of looking-bolt recesses, The cocking-piece to be hardened from the bent, including the second locking position; it is then to be tempered to a spring temper from the head to the safety bent, the full bent being left a straw colour. The cocking-piece will be examined and tested for hardening and oil blacking or browning."
Note there is no hint of Rockwell or Brinnell numbers. The entire process relies on the skilled eye and sense of timing of an experienced tradesman. Not only that, but the standard of lighting was probably not exactly uniform in the heat-treating room. Cloudy days, night shifts, hangovers......................
That's an interesting piece Bruce. It's almost archaic now and as you say, just SOO subjective too. We used an old IZOD tester to test the body locking lug and bolt lug hardness at the big Base workshops. It was a ball impact at a certain load. Certainly no Brinnell or DPN. When they were doing the trials to test the suitability of a longer bolt head, they used a similar testing method. But as I mentioned, it was soon established that if a rifle had run out of CHS on a No3 calibrated bolthead in the gauge, inspectors, bolt, then the hardness had broken through or down
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Originally Posted by jmoore
I love the story. My Kinematics instructor at MSU (I can barely define it now) worked on the WWII Bell Aircobra fighter. Propellor in front, drive shaft between the pilot's legs and back to the engine. His two favorite stories (good for at least twice a month) were landing gear breakage traced back to the maker deeply stamping nomenclature on the landing gear strut and the hydro power plant that only lost turbine blades on one turbine. The later determined that the nightwatchman was urinating on the blades on that one turbine!
Ah yes, the wonderful IZOD method. I work with a lot of milspec UK kit and almost all of the old specs call for IZOD while here in North America most of the specs I see are based on CHARPY testing. Not sure why the British penchant for IZOD, but if memory serves the IZOD test require more sample prep and therefore always annoyed me back in the day.Quote:
Originally Posted by Peter Laidler
Of course, apart from batch stock proving, most of our testing these days is NDE such as ultrasonics, LPI, etc. :)