Carbine vs. Rifle Buffer/Spring Question

[bigbrianaustin]

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.

[NugginFutz]

My 22" BHW runs both without a whimper. I installed a BTE variable gas block and with minor adjustment, now have nice little piles of brass just over my right shoulder. With 2" less barrel, your reduced dwell time should result in a slightly less energetic bolt speed, but I wouldn't hesitate going with the UBR. I would also be quite surprised if you had to open the gas port any at all.

Just remember - when you take it out to the range, pics are mandatory, or it didn't happen.

[bigbrianaustin]

Awesome. I was really hoping to hear from someone that has actually done this and that helps a ton! I think I will look into the adjustable block just for the overall performance. Thanks!

[Drifter]

Use whichever you like. The buffer system is independent from the gas system; the length of one is not determined by the other.

While there can certainly be a perceived difference between use of carbine and rifle buffer system lengths, the weapon should operate appropriately with either.

[Lead Chucker]

What drifter said. If you use a carbine buffer and spring go with a H2 or H3 buffer weight.