Using Optifine and GT++ together makes GT++ Casings render weird while looking at them from certain directions.
Normal GT casings or blocks do not suffer from this.

Using Optifine HD U D8 and the latest GT++ compiled from GitHub.

Not something I can fix.

This is caused by Casings allowing transparency.
It's one of those things that I am half minded about fixing because I'd like them to retain it and the issue is from Optifine at the end of the day..

@npawk12 What version of optifine are you using?

This is caused by Optifine's D8 shader addition + improvements on the dynamic lightning, glad its an easy fix.

I just disabled transparency. :(