So I'm wondering if G&P (metal bodies) use a proprietary G&P D-ring. I've been trying to screw on my CA delta with no luck but the threads look the right size. The only "information" I've found is on AEX with a product description for a G&P delta ring reading "For G&P Handguard Series & Marui M16 Series but must use G&P handguard. Will also work with CA handguards and rail systems." I'm assuming that these two parts do not work together seeing that I have tried myself but I was wondering if anyone else has tried the combination or has damning information...
G&P delta rings and receiver threads are slightly different than other manufacturers. Sometimes you can get parts to fit by threading them on then off, then on, etc until you clean enough space, but be careful you don't break the receiver.
I had that problem with a CA delta ring and a G&G metal body. The delta ring didnt screw down far enough to hold the barrel securly. I ended up wraping the ent of the barrel in teflon tape until it was snug enough not to need the delta ring holding it tight.