Welcome to the WWII Forums! Log in or Sign up to interact with the community.

Caliber lengths of modern main guns

Discussion in 'Post-World War 2 Armour' started by Robinson phpbb3, Jun 30, 2006.

  1. Robinson phpbb3

    Robinson phpbb3 New Member

    Joined:
    Dec 18, 2005
    Messages:
    82
    Likes Received:
    0
    Location:
    Adelaide, Australia
    via TanksinWW2
    Hey guys I was curious as to know what the calibre lengths are of
    modern main guns.

    L/ ? L7 105mm gun
    L/? Reinmetal 120mm gun
    Soviet 115 mm gun ( ie T-62 )
    Soviet 125mm gun (ie T-72/ T-80 )
    Soviet 100mm gun ( ie SU 100 or T-54)
    US 90mm main gun ( M26 Pershing M47)
    UK 120mm main gun ( Conqueror)
    US 120mm gun ( M103)
    French 105mm gun ( AMX 30 )

    Thanks guys m,uch appreciated

    Kym
     
  2. Oli

    Oli New Member

    Joined:
    May 20, 2005
    Messages:
    1,569
    Likes Received:
    0
    Location:
    Scunthorpe, UK
    via TanksinWW2
    L/ ? L7 105mm gun - L/57 (L7), L/51 (L7A1)
    L/? Reinmetal 120mm gun - L/44 or L/55 (Leo 2A6)
    Soviet 115 mm gun ( ie T-62 ) - L/49.5 (U-5T/ 2A20)
    Soviet 125mm gun (ie T-72/ T-80 ) - L/52 (2A46M1), L/51 (2A46M2), L/55 (2A46M4)
    Soviet 100mm gun ( ie SU 100 or T-54) - L/53.5 (D-10T) sometimes also L/56*
    US 90mm gun ( M26 Pershing M47) - L/50
    UK 120mm gun ( Conqueror) - L/? (L1 120mm gun)
    UK 120mm gun (Challenger) - L/55 (L30)
    US 120mm gun ( M103) - L/? (M58 120mm) Hunnicutt may give some info - I'll check Sunday night and post Monday
    French 105mm gun ( AMX 30 ) - L/56
    French 120mm gun (Leclerc) - L/52

    * I have both figures in my database (and hadn't realised until now!) - possibly because some sources give the L/ as length of rifling only and others count the full tube (including "lead-in") as part of the L/. Take your pick :grin:
     
  3. Robinson phpbb3

    Robinson phpbb3 New Member

    Joined:
    Dec 18, 2005
    Messages:
    82
    Likes Received:
    0
    Location:
    Adelaide, Australia
    via TanksinWW2
    THANKS A HEAP !!!

    That was much appreciated :)


    take care

    Kym
     
  4. Oli

    Oli New Member

    Joined:
    May 20, 2005
    Messages:
    1,569
    Likes Received:
    0
    Location:
    Scunthorpe, UK
    via TanksinWW2
    M58 gun on the M103 was 120mm L/60 according to Hunnicutt's "Firepower". Can't find a figure for the L1 120mm on Conqueror, but I vaguely remember reading that it was also used on US tanks of the period (not sure if it was a Brit design licence-produced by the US, US design design built by us or a joint project) , so may have been similar to the M58. Will have to do some more digging.
     
  5. Ricky

    Ricky New Member

    Joined:
    May 10, 2004
    Messages:
    11,708
    Likes Received:
    1
    Location:
    Luton, UK
    via TanksinWW2
    Interesting how they seem to hover between high 40's - mid 50's. Is that the 'optimum' length from a muzzel velocity viewpoint or merely a matter of practicality?
     
  6. Oli

    Oli New Member

    Joined:
    May 20, 2005
    Messages:
    1,569
    Likes Received:
    0
    Location:
    Scunthorpe, UK
    via TanksinWW2
    Aaargh! Ask an easy one. :grin:
    There's a relationship between muzzle velocity and barrel length (or more specifically, IIRC, barrel volume). And a relationship between barrel volume and volume of propellant and mass of projectile. Oh and diameter of projectile in-barrel and its mass, and gas pressure behind it... and a couple of other things.
    The main comment that springs to mind is one of Bill Sweetman's when explaining stealth - he more or less said that when you've reduced the radar signature you find that the IR emissions are higher than its radar return, so you reduce that and discover that it's IR and radar "invisible" but anyone with eyes can see it from a hundred miles away... it's a never-ending process of inter-relationships, each of which has a knock-on effect on everything else.
    It would appear (to me at least) that a certain penetration minimum is specified at a given range and then calibre, muzzle velocity and barrel length, etc. are "juggled" until an acceptable solution is found. Most probably one of several possible solutions. Long barrels reduce the utility of a tank in dense terrain (barrel overhang will affect traverse limits if you're anywhere near a tree or building for example, or overhang too much for transport in ships/ trains/ aircraft).
    We had a thread a while back about muzzle velocity versus barrel length based on a German graph taken from Peter Gudgin's book on AFV armament. IIRC this graph indicated that effectiveness started to flatten out at about 70-75 calibres of length. To get a useful velocity out of a longer barrel you'd probably need considerably more propellant to overcome the extra friction inside the barrel and keep up the pressure as volume increases. Which would make the breach larger, requiring more room in the turret and heavier trunnions and elevating gear also needing more room in the turret. Which would then require a larger turret - larger turret ring - wider vehicle - longer vehicle (to maintain steering) - heavier armour (in total, or have a reduced thickness to keep weight down) - larger engine - larger logistics slice etc. etc.
    Hmm. Sorry about the length of that.
    Short answer would be that it was a practical matter (defined threat to overcome). But note that due to increased armour on the expected opposition a good number of tank guns are now climbing in L/ value again - Leo going from L/44 to L/55 with concomitant increase in V0, or a larger calibre is being considered (140mm).
    In the late fifties(?)/ early sixties the USSR was looking at a 152mm weapon that was L/60 (which is "maybe" the basis for the 152 that is "going" to be fitted to Black Eagle).
    If that ever goes into service then where's that going to leave 120mm L/~50 guns? Ouch.
     
  7. canambridge

    canambridge Member

    Joined:
    Mar 15, 2004
    Messages:
    1,649
    Likes Received:
    6
    via TanksinWW2
    Just to back up Oli, I've read several places that optimum caliber is around 70, pretty much for all the reasons Oli has stated.
     
  8. Blaster

    Blaster New Member

    Joined:
    Jul 21, 2006
    Messages:
    1,687
    Likes Received:
    0
    Location:
    Canada
    via TanksinWW2
    RE: Modern caliber lengths

    Why aren't there any guns with lengths of 70 calibers or more today?
     
  9. Man

    Man New Member

    Joined:
    Oct 30, 2004
    Messages:
    1,457
    Likes Received:
    0
    Location:
    Norway
    via TanksinWW2
    Probably because what has been made already is sufficient... But I do not know conclusively.
     
  10. Ricky

    Ricky New Member

    Joined:
    May 10, 2004
    Messages:
    11,708
    Likes Received:
    1
    Location:
    Luton, UK
    via TanksinWW2
    and quite probably a 120mm L/70 gun would be far too long to be practical.
     
  11. Gryle

    Gryle New Member

    Joined:
    Nov 13, 2005
    Messages:
    148
    Likes Received:
    0
    via TanksinWW2
    Its possible that this 70 calibre optimum length applies to full calibre projectiles, subcalibre rounds will be accelerated faster and possibly you hit problems with how fast propelant gasses can be generated and accelerated before the projectile reaches about say 60.
     

Share This Page