One of the relatively few successful competitors to the Maxim in the early days of the heavy machine gun was the Col Model 1895 (aka, the Potato Digger). When it was adopted by the US in 1895, one of the elements in its favor was its light weight – just 35 pounds (not including mount). The Colt was an air cooled gun, which is a large part of how it was able to be so much lighter than the Maxim. This, predictably, did not sit well with Hiram Maxim, and he proceeded to make an extra-light version of the Maxim.
This version weighed in at just 27.5 pounds (12.5kg) of gun, and 44.5 pounds (20.2kg) complete with its tripod mount. That was quite impressively light, and it impressed the US trials board. However, this weight reduction was accomplished in large part be eliminating the cooling water and reducing the diameter of the barrel jacket (a jacket was still required to provide a bearing surface at the end of the barrel for the recoil action). Four cooling holes were cut in the bottom of the jacket, but these were wildly insufficient to allow proper cooling of the barrel, and as a result he gun overheated quickly. Maxim himself suggested that firing more than 400 rounds continuously would be unsafe. Why a much more heavily perforated jacket was not tried (as would be used 20 years later for the aircraft Maxims used by several nations) is not clear – it may simply have not been an idea that was considered in time.
A quick-change barrel would have helped to ameliorate the gun’s cooling liability, but this was not really possible with the general Maxim action. As a result, the Extra-Light Maxim failed to attract any significant sales, with handfuls of examples being sold here and there for evaluation and little more (for example, the company’s attempt to market a two-man, two-gun tricycle failed to gain any buyers). It did serve to keep Maxim’s name in the minds of the US military, though, and this would finally pay dividends when the US adopted a more standard Maxim gun in 1904.
Mechanically, the Extra Light was not the dead end that its commercial failure would suggest. It incorporated several new ideas, most notably a fully internal mainspring. Rather than having the mainspring (fusee) attached to the outside of the receiver, in this model it was internal. This saved space and weight (no mainspring cover need, for example), but at the cost of not being readily adjustable. That adjustability was important to the Maxim’s reliability, and the internal spring would not see further use. The other new feature of the Extra Light would become standard for all Maxim guns, however.
This second new feature was the use of an elegantly curved crank handle in conjunction with a roller cam. This made the transition from rearward recoiling motion to rotational unlocking motion much smoother than in the earlier models (in which two flat surfaces slammed together) and reduced the potential for parts breakage. This improvement (along with 12 others) was patented by Maxim in 1894 British patent #16,260.
Very few of these guns exist today, and I has the opportunity to take some photographs of one example complete with its tripod: