The recoilless weapon required a transport platform that was agile, small, light, manoeuvrable, air transportable and also had to meet a lot of other criteria. The one major factor that put a long base vehicle out of the picture was the arc of fire possible from a long base vehicle.
Remember that the concussion blast from the muzzle of this weapon was just as bad as the expelled recoil forces that were vented out the back, meaning that anything in within 30 feet in front of or behind the weapon was obliterated by concussion when the weapon was fired. Any crewman who was careless enough to step back or forward too far would have his eardrums badly and irreparably damaged. (There is a film clip released by the Army PR mob somewhere on here
http://www.youtube.com/watch?v=RDjeYePAU1s where you can see an inexperienced gunner being directed forward by his crew commander before firing on a training exercise! There is also another video floating around somewhere in cyberspace on youtube that shows some highly intelligent Libyan rebel cowboy firing a 106 from a toyota
http://www.youtube.com/watch?v=BwlrJ8Cam9I&feature=related . Both of these videos may tend to show some of the concussive forces that are expelled by this weapon.)
A 109" platform therefore, simply because of its overall length being so much longer than the weapon, severely limited the arc of fire of the carried weapon to around 40degrees either side, whereas the little shorty offered almost a 360 degree arc of fire. This arc of fire made the vehicle about ten times more versatile in a tactical hull down attack position than any long wheel base vehicle could ever offer.
It was for these very same reasons (flash points of the weapon being at the vehicle's extremities) that the original 88inch 6005 was modified so extensively to carry this weapon in the first place, and what makes a gunbuggy so unique today.
(One of the most desirable ways of ambushing a tank or two was to obtain a hull down position overlooking the expected path of the target. Fire the tracer round, then follow with the 106. Unfortunately once the major weapon was fired the muzzle flash gave away any secrecy in regards to your position, so the crew of four mounted the vehicle rather hurriedly, reversed out of the position, being ever so careful not to brake too heavily in reverse so as to avoid tumbling over end for end, then hightailed it out to the next position.
I find myself in a strange position today, as back in my much younger days attached to ADE and TPW at Monegeeta and later, Tropical Trials, I used to wonder whether most of the boffins of ADE were bits of bone heads, but then not too much later in my time I was lucky enough (In a way I suppose) to actually use some of their products in the situation for which they were designed, and today, I can look at some of their designs and put them in context with what was actually going on at the time and what was available, and blessed with the marvel of hindsight, I marvel at their ingenuity.
Regards
Glen
