stancrist said:

So a pointed grenade would not have better ballistics than with a round nose?

In general, at velocities well below the speed of sound, gentle rounded curves at the nose have lower drag.  This is largely because it is important to keep the boundary layer attached, and rapid changes in the rate of curvature, especially where the ogive meets the shank, can cause flow separation.   The attached photo WWII droptanks are good examples.   The bottom example shows one elongated with a cylindrical center section. 

A longer elliptical nose shape can reduce drag vs a half sphere as long as the projectile only flies directly into the oncoming air and not at any significant angle.   The longer elliptical noses are more sensitive to angle of attack and would not do as well with the level of wobble and pitch change experienced with current LV grenades as noted by MR T.  Longer projectiles are also more difficult to stabilize and require more spin.

The transition from the shank to the boat tail also needs to be rounded, although the length of the boattail is not as critical.    There is a certain amount of diminishing returns for drag reduction as the boat tail gets longer.   As you observed, the back portion of the boat tail can add a lot of length for the amount of payload it would carry.   That is why it is common to see a truncated boat tail.  

P-51 Drop Tanks:

The longer projectile length of most 40mm MV should give you room to improve aerodynamics but it would be at the altar of both potential HE fill and optimal fragmentation pattern. Time of flight is already better than 40mm LV by virtue of higher starting MV, so it's not clear the tradeoff is worth it over better effects on target IMO. It's an optimization problem of course, so you can have a bit of both, or a lot of one or the other

Thanks for the briefing.  Very enlightening.

Blast from the Past (1965)

Long before there was the Milkor MGL, there was the Avroc 15-40.

A multi-shot launcher that fired 40mm rocket-propelled grenades.

https://forum.cartridgecollectors.org/t/40mm-avroc-experimental-rocket-grenade/47833/9

Thats awesome, great find.

The 40 mm AVROC promotional material says "it will have a tremendous effect on future military tactics."  Well apparently not.

Couldn't find much about it on the net. Did this weapon fire standard 40 X 46 grenades with the assembly intended to extend range? 

The shape reminds me of a little mortar round. 

17thfabn said:

Did this weapon fire standard 40 X 46 grenades with the assembly intended to extend range?

I don't know.  Earlier today I spent a couple of hours searching in vain for more info.

gatnerd said:

Thats awesome, great find.

Pure luck.  It inexplicably turned up in search results when I was looking for something else.

Thats often how the coolest things are discovered. 

Some interesting videos for visual reference

Russian MGL equivalent (RG6) firing bounding VOG-25P Bounding HE

YouTube

?????? ?????????? ??-6 "????". ??????.

?????? ?????????? ??-6 "????". ??????.

Slow motion of the bound


 

YouTube

40?? ??????? ??? ??-25 "??????". 40mm GP-25 "Bonfire" grenades

??? ???????? ??????? (????????) ??? ????????????? ??????????? ??-25 "??????"???-25, ???-25??, ???-25?, "??????", ???-40, ???-25?, ???-25??, ???-40

40mm LV HEDP effect

 

YouTube

M203 Grenade Launcher

The guys from US PALM brought us some 40mm grenade launchers that we couldn't resist firing. This is from an episode of TAC-TV Season 1. In Pt. 1, we try out...