From the Firing Line Archives:
From 1998…
I was loaned an Enhanced Sigma in .40 S&W this last year. It was very reliable in one critical aspect, five rounds out of fifty would go click and no bang. No firing pin marks at all, just a click and no bang. The person who furnished the gun reported the same thing, at the same fequency. I see this with other Sigmas in a LE training academy, with one agency having a third of it's Sigmas going "click" and no bang. The same inconsistent perfromance also kept it out of consideration for a local LE degree program. In an adjoining state, the failure to fire during a gun fight is still under investigation, with the performance of the Sigma being suspect.
In the case of the LE agency with about one third of it's Sigmas going click and no bang, the guns were sent to S&W and returned with all new internals. Unknown if this fixed the problem. Other guns were not an option for this department as they were given the special treatment of "no cost" trade of 5906s (w/several pre-ban hicaps per).
The T&E gun continued to perform the same way, in spite of cleaning and using a wide variety of ammunition. It was returned.
The above was from 1998.
There same has continued since then, with some of the affected agencies moving to Glocks or Sigs. The Sigmas that continue to show up are always a problem. A local store is unable to sell police trade in Sigmas and ships them to commercial outlets in the southwest.
As of October 2003, Sigmas continue to be poor performers on the range. I have not seen any that make it to the 1,000 round count without something breaking, serious maintenance intervention or "click and no bang" episodes.