I am not a gun person and I do not have any definitive facts to contribute. But if I remember the article correctly, these were not 0.22 LR conversions or anything like. They were hand-made to order for the Infantry Board by arsenal experts. Both calibers were based on the 0.30-in Krag case. So, yes, they probably were "barrel burners". But they were meant to test a requirement, not to become service rounds. They weren't used for very long before the Ordinance Deopartment forced their withdrawal, so such problems are unlikely to have arisen. As it was, they were very popular in action and were considered entirely successful.I can find records of some .22LR Krag conversions for gallery (indoor) practice shooting. But a .177 (4.5mm) combat round sounds very unlikely any time before the 1970s. It would have to be incredibly fast/hot to have even marginal lethality and would be a real barrel burner without modern metallurgy.Unfortunately not. I recall reading an article about this while waiting for someone in the periodical room of a University library many years ago. I believe it was in the US Army Association's Army magazine, but I can't be sure after all these years.The Infantry requested .22- and .177-cal Krags so that soldiers could carry more ammunition. When the Ordnance refused, the Infantry had prototypes made and successfuly field tested both calibers until the Ordnance got wind of it and stopped the effort.
Do you have any more info on these? I'd be really curious to see the cartridges. A .177 in the early 1900s seems really unusual.
We should also remember that smokeless powder was a relatively new thing (45-70 black powder was still the de facto standards in the Spanish American War). The 0.30-in Krag was, if anything bucking the resulting trend to smaller calibers, with .30-in/7.62-mm being anything but an accepted norm at that point. The original Norwegian/Swedish Krags used 6.5x55-mm ammunition. The contemporary .276-in US Navy Lee used a 6.0×60-mm cartridge that was eventually withdrawn due to problems with barrel erosion and fouling, even though the latest nickel-steel alloy barrels were used. The 0.30 Army Krag cartridge itself proved too much for the gun's metallurgy when the Ordinance "improved" it to match the ballistics of Spanish Mausers.
Finally, as far as lethality goes, a .22 LR can kill you, even at 400 yds. So, even with a reduced powder charge, I suspect that a 5.56- or 4.5x59-mm could really kill you.