Easy-Kill said:
No, because I do not want to violate the terms of my subscription to Janes as it isn't paid for by me. I will search for the same Paul Beaver source elsewhere, but because Janes owns the IP of his work.
Article reference is not violation of any rights. Of course you can't spread the document, but you can refer to it.
Army-Technology for one is an official defence industry source.
Having read their articles on FIST and the SA80 are complete bollards. The only mention of QinetiQ was in the 'batteries' part ... Ahem. unfortunately, I don't view A-T as a reliable source because of this and other errors. Compared to Janes it's like wikipedia compared to a scholarly journal.
Army Technology is not a scholarly source, you are right there. As a source it is the industry itself. Obviously it can't be trusted in any deeper comparative analysis very much because of the very same reason, it is essentially a marketing brochure.
On the other hand Jane's is an analyst and news organization, and a good one at that. But as such it can be trusted only as much as you can any analyst and news corporation - they present one view to the matter, their own analysis from the facts they have themselves gathered.
Neither should be read like a Bible or Koran or [insert your favorite holy text here]. Both make mistakes, both have factual errors or distortions. Both should be viewed with discretion.
Without going into complex fluid mechanics, we can take a simple equation of force by air against a moving body and we see that the resistive force is proportional to surface area and velocity squared. A basic aerodynamic property of a spinning object (like a bullet/shell) will have the effect of reducing the surface area to about 1/4 (back of the mouse mat calculation). This has the effect that while the L55 has higher velocity over shorter ranges, thus more stopping power, the higher initial velocity coupled with the non spinning round and thus greater surface area, will cause the round to slow a lot faster, thus not only reducing accuracy but also velocity over longer ranges. I don't believe I stated that the L30 had a greater muzzle velocity, only impact velocity, which is what matters . I don't think there is a source with the actual muzzle or impact velocity, we will just have to trust the laws of physics.
Not going to argue physics here, but do you have numbers to show how significant the difference in aerodynamic drag really is?
According to one Andrew Jaremkow, based on information from Rheinmetall brochures, estimated in-flight velocity drop for the DM53 round is 55 m/s/km. With a muzzle velocity of 1750 m/s that would mean an impact velocity of 1475 m/s at 5000 meters. I have no idea how accurate that estimate is, but that's really not important. What is important that we do not know the data for the L30.
Even if we assumed the above figures to be correct and if Jane's is correct about L30 muzzle velocity with L23 round being 1534 m/s, we still don't know what the velocity of the latter would be at the said 5000 meters. Further I have found no data whatsoever for the newer L27 round. So unless someone comes with some relevant and reliable data, discussion on these points is rather unfruitful.
With what little information I have managed to gather I remain disinclined to believe that the L30 would be significantly more powerful in terms of kinetic energy on longer ranges, but once again I do welcome any evidence to the contrary.
why would Rod length be a factor? I can't see rod length effecting the physics but I might be wrong.
It does effect a great deal. The physics behind that is simply that the rod, while penetrating into the armor, erodes. If it is eroded to zero mass before it finds its way through the armor, it doesn't matter how much kinetic energy it has, does it?
I've heard estimations that, other penetrator qualities notwithstanding, the relation between rod length and RHAe penetration is rather linear, ie. 2x rod length ~ 2x penetration. Not knowing any more of the physics there I don't know how correct or not that hypothesis is, but what is clear is that there is a relation.
I'm not ignoring the fact that the L55 can shoot something out to 5000m. I just don't believe its relevant. The thing with smoothbores is that the round doesn't travel down the centre of the barrel, it impacts on the sides and this will cause tiny fluctuations causing the round not to go to where it is intended. This is completely random and there is no way to predict unfortunately. Thus having that range is irrelevant if you can’t hit a target. The best way to describe this effect is to look at paintballing, the balls fly all over the place completely at random This is one of the things which makes a rifled gun superior at longer ranges.
Inside the barrel the APFSDS round is guided with the sabot be it smoothbore or rifled. After the round leaves the barrel both rounds are fin stabilized (the 'FS' in APFSDS). The only difference is that with a rifled gun the fins of the round need to be angled to take the spin into account. Whether the spin really is an advantage with the fins I don't know, but in any case both rounds are primarily stabilized by the fins. Again I'm disinclined to believe that there is
major difference either way, lacking comparative data. I do know that the Challengers have demonstrated excellent accuracy in various tests and trials (they also demonstrated horrific accuracy in Greece due to bad batch of ammo) but I don't know how significant the difference to the "next best" has been.
I think we can happily put the Challenger 2 smoothbore vs rifled / L55 vs L30 debate to a rest and just agree that a) the Brits are testing the alternatives, b) we will see what conclusion they make in due course, unless someone comes up with some stunning new information not yet presented here. Next subject?
