Recoilless Rifle?

[John D Salt]

Originally posted by Sailor Malan:

[snips]

HESH (High explosive squash head) is a post war invention.

Although no HESH shells were issued for service until after the war, Sir Dennis Burney made the invention during WW2, although he called them "wallbuster" shells.

For many years from the 1950s to 1970s the British infantry's main anti-tank weapons were a splendid range of 120mm HESH-firing recoilless guns, BAT, Mobat, Wombat and Conbat.

The original BAT (Battalion Anti-Tank gun) was the subject of some extremely nicely-done operational analysis work, documents from which can now be viewed at the PRO. This pointed to the need for a ranging MG to eliminate the biggest item in the error budget. A lightly-fictionalised worked problem based on this episode is included in Shepherd, Hartley, Heysman, Thorpe & Bathe's splendid book "Applied Operational Research".

Originally posted by Sailor Malan:

Interesting point: the main reason why UK still uses rifles at MBT main armament is we don't use HEAT. We use HESH, because it is a better general purpose round (being practically HE if it doesn't hit anything too sold). I believe the AP performance is comparable, or at least each has own weaknesses when facing modern compound armour.

Even long-rod APFSDS has trouble against things like Kontakt-5 heavy ERA. I doubt that HESH would perform very well at killing modern MBTs, but there is a certain appeal to the idea of the "one size fits all" approach and making a great big bang. Even if an MBT hit by 120mm HESH probably won't be dead, it will probably be missing quite a few valuable external systems that it needs to fight (night-sights, reactive armour, radio antennas, things like that).

Personally, I think we should never have done away with the 165mm demolition gun. A 165mm HESH round would tend to rattle the teeth of any battlefield target at all.

All the best,

John.

[Olle Petersson]

Originally posted by JasonC:

The maximum effective range of the 106mm RR is not 800m, it is 8400 yards.

How do do define "effective"?

I would beleive 8400yds to be the range at high elevation, but not useful for hitting a small target.

My definition, as used by the Swedish army, is based on hit probability.

Effective range is the range at which a "trained" gunner (Not a marksman!) will have a 50% first shot hit probability against a specific target type, given that the range is known.

Given this definition I'd say 800m seem to be a likely effective range for the BAT against stationary tanks.

... They could be and were used to chuck HE like any other tube artillery.

True, but post WW2 that hasn't been the primary design objective for most RRs.

They were commonly used for direct fire at point targets at 1-2 km ranges.

... spending lot's of ammo to score a hit.

Just like the Germans used their 88mm AA guns to hit tanks at 2km in the desert, with five to ten rounds needed to score one hit.

That's beyond effective range.

Cheers

Olle

[Olle Petersson]

Originally posted by Nidan1:

I am not sure whether or not any WWII AT rounds fired from regular "guns" were ever fin- stabilized. Perhaps someone has the answer to that one.

Spin is a simple way to increase accuracy, as has been pointed out. The more spin, the more accuracy, to some degree.

It's also so that the more spin the less effective HEAT.

In WW2 HEAT was a novelty, and the warheads were relatively crappy to begin with. They were good enough to increase penetration compared to kinetic AP fired from low velocity (rifled) guns.

After WW2 HEAT became more standard issue, design and manufacturing techniques improved. Then tank guns and the like were designed with HEAT in mind, and the rifling became less steep (meaning less spin) to increase the HEAT efficiency.

Nowadays there are a couple of ways to reduce the spin of HEAT warheads fired through rifled barrels. The common ones are rotating bands or sleeve.

The latter is used for the Carl Gustav grg m/48. The warhead is too narrow to grip the rifling, and behind it is a "skirt" that grip the rifling but can rotate freely relative to the warhead.

Cheers

Olle

[Guest Mike]

Originally posted by Olle Petersson:

</font><blockquote>quote:</font><hr />Originally posted by JasonC:

The maximum effective range of the 106mm RR is not 800m, it is 8400 yards.

How do do define "effective"?

I would beleive 8400yds to be the range at high elevation, but not useful for hitting a small target. </font>

[JasonC]

Try telling any allied tanker in the western desert that 88s at 2 km were "beyond effective range". They were quite effective at such ranges, precisely because they could kill without reply. Ammo is not scarce compared to weapon systems. No reloadable weapon needs a 50% hit probability to be effective. If they did, there wouldn't have been thousands of rounds fired for every item KOed.

Yes, of course the high end ranges for the RRs are for indirect fire, as artillery. I stated already that they were used for direct fire at point targets at 1-2 km ranges, and they were. I've read AARs of Nam fights where jeep mounted 106 RRs provided a barrage to support a river crossing at ranges well over 1 km. Try that with AT-4s.

As originally stated, the point of the original German RRs was precisely HE chucking, just being lighter than conventional tube arty doing it. The point of US late war and Allied post war RRs rather than disposable infantry AT, is range.

[Stalin's Organ]

Was that barrage direct or indirect?

Certainly they could shoot that far (106's), and if there's no enemy armour arround then I'd use 'em like that too and expect them to be able to shoot so far.

But it'd be direct and I'd be hoping there were no enemy MMG's within sight because they would be impossible to see and have an effective range of a mile or more too - artillery has long known there's not much joy being within small arms range of enemy infantry when firing direct - I think the Brits found that out 1899-1902-ish!

[JasonC]

It was direct. Just plastered the whole area. The enemy certainly had MGs, but at over 1 km and under fire themselves, not much of a threat to the RRs. The whole point was to suppress such fire while infantry crossed the river in boats.

[Nidan1]

Originally posted by Sailor Malan:

</font><blockquote>quote:</font><hr />Originally posted by Nidan1:

</font><blockquote>quote:</font><hr />Originally posted by Offwhite:

</font><blockquote>quote:</font><hr />Originally posted by JasonC:

Spin reduces the effect of the HEAT principle.

Does that mean shaped-charge shells fired from our CM tanks or towed guns are less effective than warhead size would indicate? Or are they fin-stabilized? </font>

[flamingknives]

It was found that 105mm rifled guns firing APDS with a teflon driving band (to eliminate spin) was more accurate than the true 120mm smooth-bore weapons. Just enough spin was retained from traveling down the rifled tube to improve accuracy.

Why, you ask, whould spinning improve accuracy? Imagine the round has a slight flaw (to a fin or something) that would tend to make it pull off-line in flight. Non-spun rounds would pull off in one direction, while spun rounds would tend to 'corkscrew' to the taget in an increasing dispersion cone. That's why the T-62 tank's 115m gun has rifling for part of it's tube length

I was under the impression that the spin had some gyroscopic effect on the round, providing a reactive force against any external force that would try to change the facing of the projectile.

This would explain the early M16s firing .223 rounds that deflected spectactularly upon hitting leaves, raindrops etc. The gyroscopic force was not sufficient to stabilise the projectile (later models had increased rifling).

Modern Smoothbores can be ridiculously accurate - the gun mounted on the Merkava 4 is reportedly able to put consecutive rounds within the calibre of the gun (120mm) of each other at something like 1000m.

[Olle Petersson]

Originally posted by JasonC:

No reloadable weapon needs a 50% hit probability to be effective.

I never stated that, only the definition of the term "effective range".

If even lower hit rates are considered generally acceptable one could wonder why so much money and effort has been spent on increasing the accuracy and first shot hit probabilities on tank guns...

... 106 RRs provided a barrage to support a river crossing at ranges well over 1 km. Try that with AT-4s.

That would be no sweat, 'cause the projectiles can be hurled that far. It would probably be a huge waste of resources though, since each shot is one weapon, and there's probably more efficient means at hand.

Cheers

Olle