I seem to run into the problem lately at the range with the SPR18 in 243 cal. no hits after the trigger was pulled average was 3 no hits to the primer out of 20 rounds tested.
I did have the same problem also a few weeks back I think it was 2 no fire out of 25 rounds.
I went ahead yesterday and stripped the internals out from the frame seem there was a drag on poor metal fit hammer and sear.
I went at it with 600 wet@dry and now you can hear the hammer strike the firing pin and man what a difference as far as seeing the dent on the primers compare to was it use to be.
I got the trigger pull down to 3 lbs but there is still a little creep
I had some time to kill today so I strip the SPR 18 went at it again on the hammer and sear and removed the trigger creep : I tested the trigger pull at a crisp 36 oz.