Posted: 10/13/2007 9:57:23 AM EDT
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Some tanks have smooth bore guns, such as the Abrahms, and some have rifled ones, such as our Challenger. Why is there a difference of choice. I would expect the rifled gun to have more accuracy and velocity, but what are the advantages and disadvantages and ammunition selections of both designs? Mark |
I believe the British army continues to use HESH rounds, which require a rifled gun to be effective. In the case of a fin stabilized discarding sabot round, rifling would lessen its effectiveness. British tanks can shoot sabot rounds, but they must be a modified design to stop the round's spin. |
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My understanding is while the Challenger cannon is a little more accurate which allows for shots at longer range that the rifled barrel tends to wear quickly due to high velocities and the cannon has to be replaced more often to keep the advantage. So I guess the reason boil down to cost and maintenance. |
I went to a live fire display last monday and they were firing FSAPDS (fin stabilised, armour piercing, discarding sabot) rounds at targets 1100M away. See pic below. Middle rd is HESH and the left one is smoke 
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Long Rod Penetrators and HEAT rounds work best when not spun. The 'spin' from a rifled barrel disrupts the jet from a HEAT round and tends to cause LRP's to beak up on impact. To fire LRP's and HEAT rounds from a rifled barreled gun you need to fit a slip ring to these rounds to stop them spinning. There is actually no difference in 'real world' performance as both fire darts that rely on fins to stabilize them. The Brits are now swithching to the L55 120mm smoothbore cannon for the next upgrade of their Challenger II MBT's. The Brits do have a preference for HESH as their dual purpose round as it has a tremendous terminal effect on concrete building and emplaced bunkers compared to the 120mm HEAT round. Smoothbore HESH rounds are being developed by MECAR IIRC, and this removed the last obstacle to the switch. |
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Wouldn't you lose velocity on rifled barrels? Also,RPGs have fins on them to induce spin, so I can't see the HEAT rounds just flying with no spin. I think the reason is the main gun round is the Sabot which works off kinetic energy and the rifling decreases the velocity due to friction, but that decreases the accuracy of the HEAT and HESH |
Thanks for sharing!
But I believe that the British gun is apparently one of the better ones out there. Maybe that's due to it's fire control system?? |
It's just a damn fine gun. |
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Spinning a LRP causes it to precess which makes it strike off axis and it breaks. Fin stabilization is the only way. Smoothbore is slightly less accurate but it doesn't make much a problem with the size of the targets... Ditto for HEAT. Off-axis impact is detrimental to penetration. But in reality, rifling is of little use with longer, more effective projectiles. There is a limit to the length of the round. And it is impossible to stabilize LRPs with rifling alone. |
OK, you asked for it This is from my other thread on the subject We've been on a day out, courtesy of a special invite  nb, the posting of these pics has been approved We've been to a firepower demonstration, and it was a most excellent day out watching the combined forces of the British Army go through a live fire excercise demonstrating weapons systems from SA80A2 to Tornado with everything in between including 81mm Mortar, sniper rifle, Warrior, Scimitar with Rarden cannon, AS90 155mm Howitzer, Challenger 2 firing fin stabilised Sabot, Harrier GR7 and Apache  to name just a few  Piccies The Range  Snipers with std Ghillie suit and new anti thermal suit  Infantry fighting from cover  Withdrawing behind smoke cover  GMG team firing the MK19  Javelin Team  Spartan control vehicle directs 81mm mortar fire  Mortar team  FV 432's carrying 81mm mortars position for firing  Mortars land 1300m away  FV 432's withdraw after firing   Scimitar makes an appearance with Rarden cannon  Warrior  Warrior lays smoke cover   Challenger 2 makes it's appearance     AS90   Apache    Exploding anti tank mine  Python minefield clearance system   Finally for tonight.....Tornado  If you want to see more, including video's, follow this Link Mark |
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The original MI Abrams had the British designed 105mm rifled tube. It worked well, but the rifling was unnecessary because the APFSDS was the weapon of choice. To get to the next level of velocity for the the M1A1, the bore brought up to 120mm and the rifling was eliminated. |
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If you spin a fin stabilized round you defeat the purpose of the fins. If the fins are canted to cause the spinning it works fine since the round will only spin as fast as the sir over the fins makes it. Air flow over supersonic objects is very different than over subsonic objects. Flow does not actually occur over the Mach wave. The regular Bernoulli equation does NOT apply in the presence of standing pressure waves (the more generic name for a Mach wave). |
Warminster |