Bowhunters all over the United States had come to realise that a bow was now available with a maximum peak draw weight of 60 or 70lbs. which could be held comfortably at a full draw weight of 35 to 40 lbs. Archers of average strength could loose a broadhead arrow with sufficient velocity to ensure, in the event of a hit, adequate penetration of a big-game animal such as a deer.
A survey, by Allen Archery, of experienced bowhunters showed the recovery rate of big game hit using compounds to be substantially higher than with recurves.
(It might be mentioned here that probably the majority of archers in the U.K. view bowhunting with distaste, irrespective of the fact that it is illegal in this country to shoot deer with an arrow. Nevertheless a survey carried out in Pennsylvania in 1975 showed nearly 25% of hunters used a bow, yet they took only 3% of the number of deer taken by gun hunters. On these figures, even allowing for some wounding, were there two equivalent deer forests allocated respectively to bowhunters and gun-hunters, the prudent deer might display better judgment if he chose to take his chance with the former. In this connection, the Missouri Department of Conservation, in collaboration with the family of the late Wilbur Allen, in 1988 established the Wilbur Allen Memorial Wildlife Area, a 380 acre semi-forested tract near Hartville, to provide a deer reserve where only bowhunters are permitted.)
By 1976, the compound bow was legal in every state except Georgia, and 18 companies were producing 39 different models. They could be classified into three groups:
The last-named was introduced in 1974 under a separate patent application by the Martin Archery Co. of Washington. Described as having been under development for 12 years, ( i.e. since 1962) a heavy bowshaped rigid frame entirely of metal had a system of cams in the ends around which the string was led, emerging at right angles to the tips of a pair of powerful laminated bow limbs. This odd-looking contraption, more like a 'siege engine' than bow, was heavy, around six pounds; and possibly because of this and its bizarre appearance, it doesn't seem to have survived the process of evolution.
By 1977 an even more unusual bow had appeared on the American market. John H. Graham II had founded "Graham's Custom Bows" in 1969, later buying an Allen licence to build compound bows. In 1972, Len Subber had interested Graham in a gadget he called the "Zipbow"; by 1974, Subber had come up with a modified design:- an upper recurve limb of fibre-glass and wood laminations with a double "nock" attachment from which two strings descended past a handle riser. Here the resemblance to a bow virtually disappeared, as bolted to the lower part of the handle riser was a pair of rigid metal plates only two-thirds of the length of the upper limb; between the plates were the axles for twin cams, around which the strings were led and secured. Given the title of the "Dynabo", the cast of this weapon was excellent and with a let-off of draw weight adjustable from 20% to 50%, the user soon became accustomed to the rather strange 'rocking' sensation of the draw, not to speak of the very peculiar appearance of the 'bow' - vaguely reminiscent of a man standing on his knees.
This tolerance was not shared by the authorities, who promptly banned it. It had only one working limb and was therefore "not a bow". The restrictions were only lifted when a later version was produced with a lower limb of composite construction, equally short and massive, but having a token degree of flex to bring it within the rules.
(Graham sold his Allen licence in 1981, since when he continued to produce the "Dynabo", available in three models and quite popular with bow-hunters during the 1980's.
The 1977 "Archers Digest" lists 100 different models of compound bow - but fewer than 50 recurves. After only eight years in production, two thirds of the market had been taken by the compound - a remarkable phenomenon.
Parallel with the evolution of the compound bow was the development of various accessories, including release aids, with a bewildering number of types of hook, trigger, cable and strap releases the latter recalling the Turkish "flipper". If all these were not sufficient to produce a perfect loose, the deviation of the arrow as it passed the new varieties of arrow rest was minimised by the new adjustable "cushion plunger".
Coming into the 1980's. three categories of compound bow are still discernible. the tip-to-tip cable system, with an eccentric wheel at each limb tip, the limb-to-handle cable system with four or six wheels, and the "Dynabo", which by this time had displaced the "Kam-Act" from the scene: but by the 1990's 'Dynabos' had disappeared from advertisements in Archery magazines.