Poor groups with two Grendel barrels.

[A5BLASTER]

Greyfox hang on. When I check the gun again I will be back. I know the stock is a magpul carbine (milspec 368). Also the gas block slides on with ease. So should be able to use a rifle length spring if everything is built correctly or using the carbine spring means I’am compensating something to make it work. Is it ok to replace a rifle length gas system to substitute a carbine length spring as long as everything cycles normal? If I built the gun correctly would t be talking about spring substitutes?

Ok slow down and stop I mean stop lock the parking break sir.

Take us a pic of your buffer tube and stock. And don't do anything else until you post it here and we reply.

Because from what you just posted you have all kinds of wrong going on with your stock/buffer system and you don't know what's the difference between carbine and rifle length.