GBBR Help! *fixed* Hey there, I'm in need of some help. I've had a VFC HK417 GBBR since it's asia release, and I love it. built it up to be an amazing 16 in DMR. this is a rifle I use regularly; I take it to the field every weekend, sometimes even during the week, so it's seen a lot of use, somewhere around 200,000 rounds. I even managed to pick up a second one recently for CQB. I encountered an issue last week where it's not properly cycling. the bolt carrier is sluggish, and doesn't always want to lock back or feed. The problem occurs with all my mags. I even tried picking up a real steel ar-308 hammer spring, and i still get the issue. If i switch lower receivers with the one from my CQB hk417, it works fine, without any issues. the original lower give the same sluggish results with the CQB upper. I think the issue may be that there isn't enough gas getting into the blowback unit of the nozzle, which is why i tried putting in the RS spring. I'm going to check out the valve knocker block tonight when i get home, see if there is any debris, but i doubt it. i really don't want to have a scrap receiver, so I'm looking on here to see what you guys think of this issue. Keep in mind, the 417 has more in common with real steel than airsoft, parts dimension wise. I use DPMS trigger, trigger sear, and selector in my 16 in, and have been pretty much since i got it. I still use the original hammer and hammer spring until recently when i installed the RS hammer spring as a result of this issue. So, I want to know what you guys think of this issue, and you opinions on it. I'm looking forward to pretty much any ideas on this.