I was at the range today testing some loads (midrange, nothing heavy).  In the course of firing 25 rounds, I had three double fires.  NOT the double fire where it fires when releasing the trigger.  Rather, pull the triggered and bingo two rounds downrange.

this gun has a Spike's lower and was built by someone else.  He did polish the trigger sear n such and had cut one leg off the hammer spring in an effort to make it lighter and smoother.  In the past I had an occasional FTF and figured the spring was too light. So  I replaced it with a standard milspec hammer spring. I did put a matching slight bend in both legs to soften it a bit . That was a couple hundred rounds ago and I have had no more FTF's.  

I have run at least 500 rounds through it and never a problem until today.  Any ideas what is causing these two round bursts?

Oh yea, I had already decided I needed to replace the FCU.  Even if it could be tweaked to properly function. NO WAY I could ever be comfortable with it.  

got it, a borderline trigger job that probably wore through the heat treated surface material, 500+ rounds later, just enough wear to make a borderline single fire into something else............

Thanks, that's what I needed, a reasonable guess on what would cause this malfunction to suddenly appear after 6 months.  

Dano, you almost ought to tack this to illustrate what can happen when you try to do your own trigger work.

Buy a real trigger even a ALGS  would be an improvement

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