Good post Sonof and to the heart of it all.
Maybe some visual aids will help explain my assersions. I can't verify that the cause of any of this, is to do with lug contact, but it sure doesn't hurt to have two hitting solid when it does happen. I would call this event, catastophic. Watch the girl toward the last 10 seconds of it. Lucky should be her name.
http://www.youtube.com/watch?v=mn0KBzK2Kho
As for emperical evidence, the entire thread was posted in hopes of getting some cooperation from M1 and M14 owners, for evidence, by checking what I said on the lugs.
But it seems noone here is worried about it at all, that's fine too. But it does seem to be happening often enough that there are dozens of these happening now, and caught on film. Search youtube for more, by using M1, M14 or Garand KB or kabooms, rifle kabooms, etc.
Can you say for sure that lug contact did not play a part in any of it ? I would say from all my studying on the matter, and the anecdotal evidence, it has a high probability of having some degree of causation involved. At least in the aftermath.
Like this example. Note the right of bolt is shoved rearward approximately .035 or more, and the left lug is still lined up in battery with the left receiver lug. See the gap between the two ?
Keeping in mind that the right is shoved back already. What was the gap before this detonation ? I would bet money, it had no contact at all on the left side, and most likely contributed to the right side being able to be sheared off completely. Had they both been in contact fully, the right would most likely have only cracked and bent. Garand couldn't even get his to shear completely off when both lugs were contacting, even when he blew three more of them up on purpose with overcharges.
As for .003 flex in something this hard, and designed to handle this much strength,...... not hardly.
"A 1961 Watertown Arsenal study of the M14 bolt found its tensile strength to vary, as expected, from 275,000 psi at the case hardened surface to 200,000 psi at the inner edge of the case depth to 138,000 psi in the core."
I will offer for the fourth time, anyone wishing to contribute data on their lug contact of the M1 or M14, by taking a black marks-a-lot and marking the backs of the bolt lugs, then load some type dummy or sized empty case to load the bolt face with some pressure, or a lapping device with spring tension, is welcome to post their findings here, in an effort to gain more insight and data on this condition.
An empty round will load the bolt face because of pressure from the ejector spring in many cases, and give you a good idea. For those using a light, load bolt face the same way, disassemble parts from the clip area on M1's, or remove trigger guard and mag from M14'. With bolts in battery completely, use the light from underneath and up into the mag well or guts area of M1, and shine it directly up under the left lug. Move around the light and your eye until you can line it up. If you have no contact, the light will shine through easily and show a crack. There will be no doubt once you see it the first time. I use the snake neck bore light or some type bendable neck light to get in the well area. Harbor Freight carries them in stock, small size only is best. Please post what you find on all your rifles. I think many will be surprised.
To the idea that all builders already know this problem exist....Then how come this rifle came directly from one of the top builders in the country, LIKE THIS ?
Jason, I must respectfully disagree. I still maintain it is a safety issue, over an accuracy improvement option only. Place yourself in the girls shoes, and ask yourself, Do you want Two,...or One ?
