Rock River Arms NM FCG problem

[ElectronWrangler]

I just got done installing a RRA NM FCG in my AR Lower and am having a problem.

After installing the parts I performed a function check, it passed with flying colors. Then I installed my upper and went to perform the function check again, problem. When I pulled the charging handle back and released it, the bolt was held up by the hammer. Pulling the trigger allows the bolt to move forward into battery and the hammer does not follow when the trigger is released. Pulling the trigger again allows the hammer to move forward normally.

Has anyone experienced this before?

[wash]

I know that some hammers don't work with some carriers.

I think it's the area under the back of the firing pin that causes problems.

Sorry I can't help more but hammer/bolt carrier compatibility is the first place I would look.

[novalondon]

is the upper set up as a 9mm ?

[CIV Tactical]

I have seen this happen after trigger jobs on the AR. Most of the time we releive the back of the hammer just enough so the carrier cycles. you have to be carefull doing so. If you releive to much it can create lite strikes. You might have an out of spec component and may need to return the NM for another.