Hey guys, I just bought this front end kit (http://www.redwolfairsoft.com/redwo...ts_AEG_G_P_CQB_R_Kit_for_Marui_M16_Series.htm). Problem is I'm having trouble getting it on. I got my old MRE rails off, but part of it (pictured below) is still on. I nedd to either get that part of or get the same part off of my new rails. Also, I am keeping the standard length barrel, but I can not tell how to take that off either.