I have an Imbel kit and with the piston installed, I put in the gas plug and if set on A there nothing to hold it from turning.  I can simply twist it right around and it comes out.....if set on G the spring loaded pin will hold it in position.  Shouldnt the pin that goes through hold it in some how in the A position?  The notches in the gas block are kind of worn, so do I have a problem?

thanks for helping a noob

Check the ring at the end of the spring loaded pin on the plug too.  It could be worn or missing.  The pin is peened to retain the ring/washer.  Maybe simply replacing that part will fix it.  DSArms has a replacement fairly cheap.


If that doesn't do it maybe the gas block is bad.

Here are some pics showing it.  
Notice the gap between the plug and notches.  It looks like the plug doest fit flush enought to catch on the grooves in the gas block.