Rifled vs Smoothbore Barrels

Discussion in 'Tanks, planes & ships' started by Ignorant_Layman, Apr 25, 2011.

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  1. This is a debate I've stumbled across here a few times. From what I can gather, smoothbore seems to have won the argument insofar as Challengers (the only big name tanks which were still using rifled barrels?) are now being fitted with smoothbores, but a fair few people continue to defend the rifled barrel, citing HESH capability and a particularly long range kill achieved with a rifled barrel once during the Gulf War.

    I must confess my personal knowledge of the subject is very cursory, coming largely from forum searches and checking out "ra ra" videos such as the following:


    (Skip to 1:50)

    Could someone more in the know explain the debate? If rifled barrels really do have better range and accuracy, why the primacy of the smoothbore? Is losing HESH (high explosive squash head?) really that big of a deal, and was it primarily an anti-armour round (as described above) or a round for use against fixed positions (as I've read elsewhere)? Is it true that it's much hader to use autoloaders with a rifled system? Is it all just a question of cost and going with what's more mainstream and has the spares and upgrades which are easier to get hold of?

  2. I do believe the reason was due to cost and little else.
  3. Is it really that much more expensive?
  4. As far as KE ammuntion is concerned, smoothbore is the way to go. Fin ammuntion doesn't like being spun, so our APFSDS ammuntion has to be fitted with a slipping driving band.

    Unguided 'fat' CE rounds HESH do need to be spun for maximum acccuracy, and our penchant for the HESH effect led us to continue with rifled barrels long after everyone else had gone smooth (also consider RARDE's initial lack of enthusiasm for APFSDS). However recent advances in ammunition technology means that you can probably get just as good (if not better) effect from a 'smart' smoothbore projectile - and there lies the problem: in continuinng with a rifled system, we are not able to take advantage of most of the recent advances in ammuntion technology, which are nearly all developed for the German-derived 120mm smoothbore system.
  5. Throughout the history of tank guns, they have almost exclusively been rifled weapons. Rifling of the barrel imparts spin on the projectile, improving ballistic accuracy. The best traditional antitank weapons have been kinetic energy rounds, whose penetrating power and accuracy decrease with range. For longer ranges, high explosive anti-tank rounds are better, but accuracy still suffers and for extremely long ranges, anti-tank guided missiles (ATGMs) are considered to have a better chance of hitting the target.

    In the 1960s smoothbore tank guns were developed by the Soviet Union and by the experimental U.S.–German MBT-70 project. Based on their experience with the gun/missile system of the BMP-1, the Soviets produced the T-64B main battle tank, with an auto-loaded 125 mm smoothbore high-velocity tank gun, capable of firing APFSDS ammunition as well as ATGMs. Similar guns continue to be used in the latest Russian T-90, Ukrainian T-84, and Serbian M-84AS MBTs. The German company Rheinmetall developed a more conventional 120 mm smoothbore tank gun which does not fire missiles, adopted for the Leopard 2, and later the U.S. M1 Abrams. The chief advantages of smoothbore designs are their greater suitability for fin stabilised ammunition and their greatly reduced barrel wear compared with rifled designs.

    Tank gun - Wikipedia, the free encyclopedia
  6. HESH, AIUI, was first introduced as an anti-fortification projectile in the forties, but post-war usage shifted towards anti-armour because it was effective against very thick steel armour and more-or-less velocity insensitive so it could be used on ATGW and recoilless rifles. Considering the technical layout, it would also be substantially cheaper to produce a HESH warhead than a HEAT (Shaped Charge) one.
  7. After the war, we Brits came to the opinion that HESH would be a more effective anti-armour round than HEAT - partly because HEAT rounds at that time were comparatively poor in terms of penetration, and partly because we invented it.

    Tis thinking pervaded almost evrything we did, so that in addition to HESH rounds as secondary tank gun ammuntion, we also used it as the primary warhead for our Recoiless Rifles and our first ATGW, the Malkara.

    Problem was, as soon as armour moved away from monolithic steel, the HESH effect was pretty much negated.
  8. APFSDS ammunition is considered totally indispensible, then?

    You've reminded me of another point I'd seen people making: rifled barrel ammo is apparently "multi-part" and thus less convenient/more complex than its smootbore counterparts (also costlier). Why is this - is it because of stuff like the "slipping driving band" you mentioned needing to be fitted to certain ammo types to overcome the spin imparted by rifling?

    Why couldn't sabots designed to spin be introduced instead?
  9. At the moment, KE fin ammuntion is the most reliable way for a tank to kill another tank.

    Rifled ammuition does not necessarily need to come in two parts - that's just the way our system is designed.

    Ammunition with a high length:diameter ratio (i.e APFSDS) is stablised by fins, rather like an arrow, and spinning tends to make it less stable. The slipping driving band allows the sabot itself to stay more or less 'un-spun' as it travels down the barrel.
  10. More points:
    APFSDS doesn't particularly mind being spun a little bit. In fact it is beneficial as long as it isn't too fast (evens out aerodynamic effects from manufacturing flaws). A problem is that it is too long and thin to be stabilised by the spin and the fins necessary to stabilise it aerodynamically will de-spin it in very short order - fast enough to damage them and thereby degrade performance further out.

    The current 120mm smoothbore ammunition is one part. The current L30 rifle ammunition is two-part. There is no particular reason that either can't be the other way round. Cost of rounds is partly due to technical aspects but mostly because there are about four or five hundred tanks out there using the 120mm rifle and four or five thousand using the 120mm smoothbore. Thus the development cost is spread out over a much larger number of rounds produced for the smoothbore and each round is cheaper.
  11. Thanks for all the info, guys. Another supplementary question: what is it about HESH that makes rifling so necessary, anyway?
  12. Basically, the same reason you spin an artillery shell, or a 5.56mm bullet - spin stabilization of a short L:D projectile.

    Probably could be done with fins (like the US MPAT round), and some sort of semi-smart guidance, although you might lose a bit of explosive payload.
  13. IANAE
    It's only travelling at 670 ms so it is lobbed, it will thus be smacking into the target at nearer a right angle(1) thus the shock waves will be travelling the shortest distance through the armour, additionally the round is base fused and ideally one wants to achieve a cowpat effect to get maximum effect from the round. I suspect it would be inordinately difficult to achieve that effect with a fin-stabilised round from a gun.
    (1) See 3:12 in the vid above, range is only ca1600m. It also gives quite a good chance of hitting the turret roof, one of the weaker area in all AFVs, hence the BILL A/TK missile in service with the Swedes and others.
  14. It seems the OP has a parallel thread running in the RAC forum. Perhaps these could be amalgamated, as there is quite a bit of cross-over (Moderators?).
  15. Just a quick thought, the Indians use 2 piece rifled ammo on there MBT, can we not collaborate with them for cheaper ammo, didnt we borrow some a while back tor firing trails?