05-20-2014, 04:22 AM
I am getting ready to reassemble my Grendel upper and have decided to build a dedicated lower for it rather than use a multi-use one I had planned on. The barrel I have is a 20" Blackhole Weaponry, and I need some advice on the buffer/spring. I understand the reasoning for using a rifle length tube and spring such as an A5, but would really like to use a Magpul UBR instead, or possibly use a MFT Minimalist for pack hunting/weight purposes, and cannot find a definitive answer on the subject. I have seen some mention of opening the gas port in the barrel slightly to add more gas to the system to run with a carbine buffer, but others say they've used a carbine buffer setup with a rifle upper and had no problem. Considering looking into an adjustable gas block which may negate the need for the modification, but any advice would be phenomenal and greatly appreciated.