From what we have gathered on this thread it seems that there were three basic issues with the Sten: 1) The tendency to discharge when dropped or bumped. From what I can tell, this was possible on the Mk.II and Mk.III Sten when the bolt was forwards and the butt of the gun received a shock. The cure appears to have been a field modification in which the safety device of the Mk.V was added to the Mk.II and Mk.III. This was certainly done in Normandy, although we don’t know in detail what this modification was, or whether it was 100% successful. 2) The tendency to run away. This was caused by certain early batches of ammunition, and the cure was improved ammunition. However, we have no reports that indicate that this was an issue on active service, and we have evidence asserting that it was cured before D-Day. Again, we don’t absolutely know if the improved ammunition was a 100% cure, as there may be later reports in existence that indicate otherwise. 3) The tendency to jam This appears to have mainly been due to the design of magazine, which was double column/single feed and copied from the Germans. This tendency to jam was enhanced by a) ambient dust, and b) poor quality magazine springs. The Germans appear to have had exactly the same problems with jamming and ambient dust on the MP 40, although I don’t know if they had the same issues with the magazine springs. The article on Wikipedia on the MP 40 puts a brave face on things, but it is clear that it had broadly the same issues as the Sten: The openings in the Sten’s body for ejection and for the travel of the cocking handle also permitted dust ingress, but again these don’t seem to be significantly larger than their equivalents in the MP 40. While the Thompson was definitely superior in this regard, having a double column/dual feed magazine, I can’t see any obvious reason why, given adequate ammunition, the Sten would be any less reliable than an MP 40.