The Bristol Blenheim's Strafing Potential

[Knouterer]

Like other nations, the British had rifle-calibre armour piercing ammo - it wasn't exactly new technology by 1940. And the RAF used it on a large scale.
From a 1929 War Office manual:
"The design therefore takes the form of a hardened steel core enclosed in a bullet envelope, and to enable the bullet to set up in the rifling, a lead sleeve is provided between the core and the envelope. (...) This bullet is used is used in conjunction with an ordinary Mark VII case loaded so as to give a nominal muzzle velocity of 2,500 feet per second.(...) With well made cores this bullet should penetrate a 10 millimetre armour plate of good quality at 100 yards practically every time."

Ammunition destined for the RAF ("Red Label") was subject to more stringent quality control, to minimize the risk of hangfires and misfires.

I might add that with a fighter strafing targets on the ground (or at sea) you have to add the speed of the plane itself to the muzzle velocity, which would make another 300 fps or so and increase penetration somewhat.

There's no reason to believe that the British rounds were markedly less effective than German rounds of very similar construction. That bullets would tend to glance off armour plate angled at 60° is hardly surprising, the same would happen to German bullets.

In fact, a German Army manual gives the same performance for the SmK (Spitzgeschoss mit Kern) round: "Durchschlagsleistung etwa 10 mm auf 100 m".

To return to the subject at hand, it is clear enough - to me at least - that the hulls of the barges, the tugs, the trawlers, the Vp-Boote, the R-Boote etc. etc. of the Sea Lion fleet offered little or no protection, not even against ordinary .303 ball, which could penetrate up to 20 mm of soft steel.
Only exceptions: the M35 minesweepers and the SAT, which were (very) partially armoured - as noted before.

And that concludes my public service announcement.

[Gooner1]

To return to the subject at hand, it is clear enough - to me at least - that the hulls of the barges, the tugs, the trawlers, the Vp-Boote, the R-Boote etc. etc. of the Sea Lion fleet offered little or no protection, not even against ordinary .303 ball, which could penetrate up to 20 mm of soft steel.

That would depend on what part of the Channel they were in, apparently ..

[phylo_roadking]

"Tests by the RAF indicated that both the .303 and 7.92mm AP bullets had some problems penetrating the structure of the relatively small and light Blenheim bomber.

Interesting. And would these bullets be in any way comparable to the German 7.92 mm AP bullets that according to you were such a serious threat to British light tanks?

The German 7.92mm ammo that was a threat was SmK, a special type of bullet designed to be armour-penetrating. German armour specifications for e.g. the Panzer I or armoured half-tracks asked for the armour to be 'SmK proof'.

I don't know if there was a .303 equivalent in terms of bullet to SmK and if so, what its specs were.

I also don't know whether the Mk. VI light was SmK proof. I understand carriers were not.

This ends this public service announcement.

Hi Urmel - there was also the SmKH....Spitzgeschoss mit Kern, Hart...which replaced the tool steel core with a tungsten carbide core. This came into service in 1939.

If you remember this was discussed on and off the forum last summer; only the MkVI's frontal surfaces were 15mm (in the MkIVB, 14 in others)- side, rear and top was 4mm. And the SmKH could penetrate 18mm of armour. According to Tony Williams - both on tank-net and here on AHF - SmK would actually penetrate 13mms of rolled homogenous armour at a 90-degree angle from 100 metres one time in every three...

The SmKH was a rare round due to the cost, obviously - but "rare" is a relative thing; just over 8 million rounds of it was produced in 1939 alone compared to around ten times that in SmK. I've found some comments that it was "mostly" supplied to Pz.I crews to make some use of that vehicle once war came - but since finding those I've also found confirmation here on AHF that every landser was issued ten SmKH rounds in the first two years of the war, both for personal use in their K98, and also to contribute to their squad's MG34.

For comparison to the Vickers Light tanks' 14mm(15mm in the MkVIB) frontal armour and only 4mm side armour - the gun shield of the 2 pdr A/T gun was 7.9mm thick...and the Bren Gun Carrier 7-10mm depending on the location on the vehicle. Thus in 1940 both SmK and SmKH gave the average landser some capability against light armour, even with his own battle rifle...

[phylo_roadking]

Like other nations, the British had rifle-calibre armour piercing ammo - it wasn't exactly new technology by 1940. And the RAF used it on a large scale.
From a 1929 War Office manual:
"The design therefore takes the form of a hardened steel core enclosed in a bullet envelope, and to enable the bullet to set up in the rifling, a lead sleeve is provided between the core and the envelope. (...) This bullet is used is used in conjunction with an ordinary Mark VII case loaded so as to give a nominal muzzle velocity of 2,500 feet per second.(...) With well made cores this bullet should penetrate a 10 millimetre armour plate of good quality at 100 yards practically every time."

To be reasonably proof against .303 AP rounds - of which the RAF had a reasonable supply, 28.8 million at the beginning of June - you'd need about 15 mm armour plate...

So the penetrating capability of the .303 AP seems to have shrunk by 33.3% already..

[phylo_roadking]

To return to the subject at hand, it is clear enough - to me at least - that the hulls of the barges, the tugs, the trawlers, the Vp-Boote, the R-Boote etc. etc. of the Sea Lion fleet offered little or no protection, not even against ordinary .303 ball, which could penetrate up to 20 mm of soft steel.

That would depend on what part of the Channel they were in, apparently ..

Indeed it would.....as Knouterer is using THIS example of the Bristol Blenheim's anti-shipping capability -

To be reasonably proof against .303 AP rounds - of which the RAF had a reasonable supply, 28.8 million at the beginning of June - you'd need about 15 mm armour plate, and there was hardly a scrap of armour in the entire invasion fleet as far as I know (only M35 minesweepers and SAT were partially protected).
To illustrate the point, here's a picture (from G. Naims and L. Frädrich, Krieg im Ärmelkanal) of the wheelhouse of a German Vorpostenboot, either V 1509 or V 1511, after being machine-gunned by a Blenheim (bomber) on 31.3.1941. The caption says crews on the bridge repeatedly suffered losses (the boats of this particular Vp-Flotilla were finally fitted with armour protection and gunshields from September 1941).

Because...on 31.3.1941 a Vorpostenboot was (just by coincidence? I'm awaiting confirmation that it was the same Vorpostenboot, or not) attacked off the Dutch island of Texel by an antishipping sortie of No.21 Sqn, Bomber Command from RAF Watton...

And while that light damage was being done...I did note previously that the Vorpostenboot had had to be able to make it to port to have its damage photographed thus...what was the Vorpostenboot itself doing?

Shooting down TWO (2) of No.21 Sqn's attacking Blenheims, R3884 (F.Sgt P.A.Adams/F.Sgt T.R.Alston/F.Sgt R.E.Nichols) and R3900 (PO D.A.Rogers/PO W.L.Gourlay/F.Sgt G.H.Howard)

Being shot down by defensive fire tends to cramp the style of strafing aircraft.

[Marcus]

An uncivil post by Knouterer was removed.

/Marcus

[phylo_roadking]

Marcus - part of the post did raise a valuable question...

If a given .303 AP round penetrates 10mm of armour at 100 yards "practically" every time...penetration will of course drop off with distance...and closing to 100 yards of a ship on water doesn't leave a pilot much time to pull out of even a shallow strafing dive RAF pilots had a number of other practical considerations to bear in mind...

Nor do we happen to know from the above how sharply penetration would drop off between 10 and 15mms of armour....it is, after all, a 50% increase in thickness.

[Knouterer]

Another interesting shot of a Vp-Boot of the same Flotilla after an encounter with the RAF. No comment necessary I think. The caption says that the joke among the crews was:
"What's the difference between a Vp-Boot and a teastrainer?"
"A teastrainer doesn't have so many holes."

[phylo_roadking]

Another interesting shot of a Vp-Boot of the same Flotilla after an encounter with the RAF. No comment necessary I think.

However - it's worth noting again that said teastrainer seems to have made it to port under control...as opposed to the oft-assumed floundering about in the Channel causing chaos and confusion. Which is the appropriate point to take from that pic in the context of this thread.

[Knouterer]

My "uncivil post" made the valid point that - contrary to what Phylo suggested - there is no contradiction whatever between my statements that a) a .303 AP round could penetrate about 10 mm and b) you would need about 15 mm to feel reasonably safe when dozens or hundreds of said rounds are hitting the armour plate you're behind, and that remark about a "reduction of 33%" of penetrating power just doesn't make any sense at all.
Sorry.

[phylo_roadking]

My "uncivil post" made the valid point that - contrary to what Phylo suggested - there is no contradiction whatever between my statements that a) a .303 AP round could penetrate about 10 mm and b) you would need about 15 mm to feel reasonably safe when dozens or hundreds of said rounds are hitting the armour plate you're behind....

As I noted above - you don't know this; you don't know how sharply penetration would drop off between 10 and 15mms of armour....it is, after all, a 50% increase in thickness.

And you've left out the important caveat regarding distance - that a .303 AP round penetrates 10mm of armour at 100 yards.

[Knouterer]

Another interesting shot of a Vp-Boot of the same Flotilla after an encounter with the RAF. No comment necessary I think.

However - it's worth noting again that said teastrainer seems to have made it to port under control...as opposed to the oft-assumed floundering about in the Channel causing chaos and confusion. Which is the appropriate point to take from that pic in the context of this thread.

Oh if THAT's the point you want to argue ... I don't doubt at all that at least part of the Sea Lion fleet would escape and make it back to port without being sunk

[phylo_roadking]

And regarding the fleet's ability to defend itself, as mentioned in the previous thread, now closed...

What Schenk actually writes is that 19 of the transports from Rotterdam were armed with one or two field guns - but not before October or November.

In general, it seems that the picture painted by Schenk as regards the German preparations is a bit too rosy. For example, he notes that the 35th Infantry Division intended to arm 20 of its barges with captured 75 mm (Schneider) guns, but the War Diary (Kriegstagebuch) of the division notes for 15.9 that only three of the twenty had been delivered and the gun crews had not been trained yet. And apparently, as of 28.9 installation had still not been completed.

What Schenk actually writes is...

The barges were armed with the small arms and machineguns of the troops on board, and additionally with 7.5cm guns. The 35th Infantry Division intended to fit twenty of their barges with 7.5cm guns, fifteen with PAK anti-tank guns, light field or mountain guns, thirteen with 2cm flak and the remaining twenty-six with machineguns of FlaMG. The 17th Division planned to arm all forward barges in a tow with a 7.5cm gun and all rear barges with a 2cm flak or FlaMG.

...which would of course be the FlaMG and 2cm flak of the units boarded. That's a lot of LAA around...as well as MG fire from the troops on board; and in the case of 17th ID...

..and all rear barges with a 2cm flak or FlaMG...

...all tows would have at least a 2cm flak or FlaMG in addition to whatever small arms and MGs on board.

If a single Vorpostenboot could bring down two attacking Blenheims - what is all that AA going to do?

[Knouterer]

So, in short, what I said that Schenk actually writes is in fact what Schenk actually writes, namely that the 35th ID intended to arm 20 of its barges with 75 mm guns. I'm glad we agree for once, although I don't see why you feel the need to bring this up?

[phylo_roadking]

Because you neglected to mention what he said about all the small arms, infantry MGS...and 2cm flak and FlaMG. The defensive weapons against air attack that would have been mounted when their owners boarded the barges.

Essential detail in a thread regarding air attack on the invasion fleet.