It could knock a cavalryman clean out of his saddle
Since points and feathers vanished in the seabed it is not possible to be precise as to the spread of arrow-weights retrieved from the Mary Rose. Best indications are they must have weighed in at between 500 and 1500 grains.
The draw-weight of longbows retrieved supports this range, running from flight (or bearing arrows) through to the heaviest (or Military Arrows).
For many years the heavier end of the longbow fraternity has tested their skills at shooting the Standard Arrow. The weight of that arrow has long been set at 800 grain with a shaft thickness of 3/8 inch. However, even such an arrow does not fully challenge those who shoot at the top-end of longbow draw-weights. It seems only fair they should have the opportunity to shoot an arrow that comes nearer the top-end of arrow weights. Both the Mary Rose finds and the interest of the challenge point to 50% weight premium for the Military Arrow over the better known Standard Arrow.
The most practical definition of the Military Arrow is therefore one that weighs in at a minimum 1200 grain and has a shaft thickness of ½ inch. As to the further definition, we can follow existing practise; i.e. 31.5 inch inside (self) nock to the socket of the head (forged steel).
The higher weight demands longer fletchings. Feather length is the limiting factor and one can hardly go with 9 inches. Indeed, the Mary Rose arrows indicate that a 7 1/4 minimum length over the quill is appropriate. The minimum height should be 3/4". Some of the longbow companies on this website shoot the Military Arrow.
The I.L.A.A. drafted the outline parameters of the military Arrow when the Mary Rose data became available.
The Unitie Laudable and Fraternitie of Prince Arthur took up the Military Arrow some years ago at its private venues.
The Compagnie du Duc d’Alba is one of two companies in France that have encouraged the use of the “Flèche de Guerre”, which is of the similar configuration.
The Company of the Finsbury Archers recently tried it out at one of their shoots (Feb 2007).
The Fraternity of Saint George has incorporated the Military Arrow within its overall warbow challenge; the International Mary Rose Warbow Trophy which is held in mid July every year.
And finally; this is a very heavy arrow. Unless the bow is very heavy also the bow will "tire" and lose its cast. A military arrow should not regularly be shot out of a bow of less than 110 lbs.