"THAT" rifle... SLR freaks need not get excited.

Discussion in 'The NAAFI Bar' started by Negligent-Discharge, Feb 1, 2013.

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  1. Negligent-Discharge

    Negligent-Discharge LE Book Reviewer

    I was a having a few beers with mates and talk turned to the best rifle an infantryman could want. The blessed SA80 came up in conversation and some bloke claimed that as the propellant ignited that at some point there was the equivalent of 20tons to the square inch in the chamber. I suggested "Bollocks". There are a few Pints riding on this. Anyone got any idea?
     
  2. 55000 psi as a maximum SAAMI spec., so about 27 tons or so.

    Get 'em in, and bad luck!
     
  3. For two pints and a packet of cheese and onion crisps, I'll produce a post saying that it's only about 10 tons. You could then print it off, show it to your mate and collect the winnings. Deal?
     
    • Like Like x 2
  4. Sorry - was just passing - did someone mention it?
     
  5. When the propellant ingnited in an SLR the pressure was equal to 1 megaton.

    Nursey? Nurse!
     
    • Like Like x 5
  6. That much? I recall the proofmark on my SMLE was 18 tons per square inch or so.
     
  7. Negligent-Discharge

    Negligent-Discharge LE Book Reviewer

    I think I'm in the clear if I put my pedant's hat on... so far I've seen 19 tons and 27 tons... not 20. Puttessinmyhands, yer on! Let's fix it at 14.7 lbs to the square inch...
     
  8. 20 tonnes "20T" is the current UK and CIP proof test for 7.62mm and .308W rifles. This is a slight increase from the 19T that used to the standard from the 1960s to the 1990s.

    Operational pressures are about 70% less than the proof load. Oiled ammunition produces a thrust on the bolt face of about 50% less than the proof load.

    (Oiled cases allow a limited rearward movement of the case - hence increasing pressure on the bolt - before the oil is squeezed out and the case grips the chamber walls)

    Hence .303" has about 8-10T dry ammo pressure, 12-13T oiled ammo pressure (on the bolt), and an 18T proof load. Even the proof load is well under the safe limit for a typical rifle - Lee Enfield No1 rifles were easily capable of withstanding sequential 30T proof loads....
     
  9. Negligent-Discharge

    Negligent-Discharge LE Book Reviewer

    4(T)... you're scarey with that amount of info first thing in the morning...
     
    • Like Like x 1
  10. 4(T)s post reminds me of the almost eternal debate about 308/7.62 converted Lee Enfields and how they were allegedly unsafe. L42A1/L39A1 were perfectly OK in my experience, which in the light of 4(T)s post is hardly surprising.
    As an aside even 357 Mag proof load produces about 35000 psi or 17 tons ish. 9mm is about 32000 psi.
     
  11. ugly

    ugly LE Moderator

    We can all thank NZNRA for that particular balls up!
     
  12. .
    What about the .22 calibre Cadet GP SA80 variant?
     

  13. Its late in the afternoon where I am, and the alternative to surfing Arrse and writing about my favourite subject is wading through twenty-page Excel sheet business plans.....
     

  14. A combination of the septic internet urban myth industry, compounded by outrageous fabrication and fcukwittery by UK NRA....
     
  15. CanteenCowboy

    CanteenCowboy LE Book Reviewer

    Jesus, with all this technical knowledge flying about it looks like this thread has been taken over by some 'ginger haired stepchildren' from the SASC.