Semi-automatic gear on 6 pounder and 17 pounder

Discussion in 'Weapons, Technology & Equipment' started by Don Juan, Jun 18, 2015.

  1. Don Juan

    Don Juan Well-Known Member

    I've read that both these guns had a semi-automatic gear, presumably to increase their rate of fire. Is anybody able to inform me how this worked? Thanks in advance...
     
  2. BrianM59

    BrianM59 Senior Member

    I know the RAF and Navy used a semi and fully automatic version of the 6pdr OQF - the Navy in twin turrets but the type mounted in Motor Gun Boats and on Mosquitoes as a tank buster was a Molins gun - with a power loader. This http://fhsw.wikia.com/wiki/Sp_6_Pdr_Molins is a gaming website with the gun mounted in a fantasy secret weapon Cromwell, but there is a video from the History Channel showing the loader working. This http://www.combatreform.org/cannonfighter.htm is better - a combination of spring loaded feeder and gravity by the sound of it.

    In Warship by John Jordan, there is discussion of a semi-automatic, radar controlled 17pdr (3.3"), intended for us in the Brave Class of fast patrol boats, but cancelled in 1956? Can't see anything else for the 17pdr.....
     
  3. Tricky Dicky

    Tricky Dicky Don'tre member

  4. Don Juan

    Don Juan Well-Known Member

    Thanks gents, but I don't think these are what I am looking for. The semi-automatic gear was (I think) fitted to all production 6 and 17 pounders - it was a standard part of the gun. My guess is that it wasn't an auto-feed, but was some kind of auto-eject.
     
  5. idler

    idler GeneralList

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  6. Don Juan

    Don Juan Well-Known Member

    Thanks very much idler - that looks like the thing.

    I've read in a 21 AG report that the reason they could not reduce the charge in the 17 pdr HE was because it would affect the operation of the semi-automatic breech, so I'm assuming the operation of the breech must have been at least partially dependent on the pressure built up by the propellant.
     
  7. idler

    idler GeneralList

    That's interesting as I once looked into when half-charge HE came in, and couldn't work out why it hadn't been tried during the war.
    I have to admit I don't know the workings of the semi-auto mechanism but I wouldn't have thought it was 'gas operated' as I wouldn't want the breech opening while the barrel was above atmospheric pressure!
     
  8. idler

    idler GeneralList

    That's interesting as I once looked into when half-charge HE came in, and couldn't work out why it hadn't been tried during the war.
    I have to admit I don't know the workings of the semi-auto mechanism but I wouldn't have thought it was 'gas operated' as I wouldn't want the breech opening while the barrel was above atmospheric pressure!
    Back to the point - they were clearly considering reduced charges during the war - could you share the file ref, please?
     
  9. idler

    idler GeneralList

    That's interesting as I once looked into when half-charge HE came in, and couldn't work out why it hadn't been tried during the war.
    I have to admit I don't know the workings of the semi-auto mechanism but I wouldn't have thought it was 'gas operated' as I wouldn't want the breech opening while the barrel was above atmospheric pressure!
    Back to the point - they were clearly considering reduced charges during the war - could you share the file ref, please?
     
  10. rick wedlock

    rick wedlock Member

    I have the semi auto gear you mention on my Cromwell, the mechanism ejects the empty case and cocks the breech ready to accept the next round, so basically the gun will fire as fast as the loader can shove the round into the chamber, which in my estimation would be around 3 or 4 seconds. hence the term QF, however the gun must travel fully to the rear to enable this


    rick
     
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  11. Don Juan

    Don Juan Well-Known Member

    Thanks Rick.

    Perhaps the reason they couldn't reduce the charge in the 17 pounder HE was because the round would not produce enough recoil to guarantee full travel to the rear and thus re-cock the breech.

    That makes a bit of sense.
     
  12. idler

    idler GeneralList

    Now I'm wondering if APDS had a larger charge to offset the lighter projectile to maintain an adequate recoil force? It's certainly an angle that hasn't occurred to me before.
    My understanding is that the postwar 105mm tank gun used half charges for HE (which was then capitalised upon in Chieftain where bagged half-charges took up half the amount of stowage space) so they may have successfully 'balanced' full charge APDS and HE - full bore shot having gone out of fashion.
     
  13. idler

    idler GeneralList

    The Centurion's 20pdr is the earliest reference I can find to the use of both high- and medium-velocity ammunition, in its case APDS and HE.
     

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