I think they were a bit larger than that - see below excerpt:
The solution was to replace the gun with a small solid-fuel rocket engine, mounting a warhead similar to that of the cannon shells. The R4M in fact used a much larger warhead of 55 mm, one that was selected to guarantee a kill with a single hit. Each R4M weighted 32 kg, and was provided with enough fuel to be fired effectively from 1000 m, outside the range of the bomber's defensive guns. A battery typically consisted of two groups of 12 rockets, and when all 24 were fired at once they would fill an area about 15 by 30 m at 1000 m, dense enough that one was almost certain to hit its target. The main body of the rocket consisted of a simple steel tube with flip-out fins on the tail for stabilization. Two warheads were available for the R4M, the common PB-3 with a 4 kg shaped charge for anti-aircraft use, and the larger PB-2 for use in the anti-tank role.
Only a small number of aircraft were ever fitted with the R4M, mostly Messerschmitt Me 262's, which mounted them on small wooden racks under the wing just outside of the engines. In service the weapon proved deadly, with one attack in April 1945 downing 30 B-17's for the loss of only three Me 262's. However by this point the war was already over.
After the war the R4M served as the pattern for both the US 2.75 in (70 mm) FFAR (Fin-Folding Aerial Rocket) and the larger 5 in (127 mm) Zuni.
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32 Kg per rocket is a little over 70 lbs per - total battery of 24 rockets is nearly 1,700lbs. I don't think we can get that on a Nieuport, but we might get off the ground in a SPAD
EagleDNY
$.02
