Originally Posted by tinbucket
Home page Firearms Talk has an article about the Army has developed a new lighter machine gun shooting a larger bullet, in a polymer case.
I wonder if it is all sorted out?
Polymer cases have always had a lot of problems, in particular another design or caseless ammunition.
Cookoff was one.
A plastic case melted, in the chamber?
It went through a lot of rounds though.
Polymer cases are a step backwards. We developed caseless ammunition decades ago. Cookoff is a problem with any automatic firearm. Brass casings can absorb some of the heat from the chamber, but if you let a brass cased round sit in a hot chamber too long it will light off, too.
In any event, caseless cartridges using propellants with high ignition temperatures actually have less of a cookoff problem than brass cased ammunition. However, they still can and do cookoff.
The biggest problems with caseless cartridges have been chamber obturation for firing, feeding, and preventing degradation of the propellant from moisture, chemicals, and UV.
The HK G11's mechanism was complicated by the requirement for an extremely high burst rate of fire, something like 2200RPM, that was borne out of a requirement for a rather silly improved hit capability. For infantry, appropriate optics and training do far more to improve first round hit than high firing rates.
High firing rates mean something more in the context of weapon systems mounted to vehicles moving at high velocity, typically aircraft.
LSAT is about giving individual infantrymen more rounds per man than current technology allows for. The thinking is that if our infantrymen can carry double or triple what our enemies can carry, then our guys can sustain themselves longer in a firefight than our enemies. The low cost, lethality, and prevalence of high explosives on modern battlefields largely makes better small arms technology a moo point, like the opinion of a cow.
Small arms, bullets of all kinds really, aren't responsible for the majority of casualties on modern battlefields whereas weapons that use high explosives are. In any event, better small arms technology is still better. Any advantage we can give our soldiers should be actively pursued.