The CAV-15 lower receivers from GWACS Armory are popular among lightweight AR-15 builders. Their two piece polymer construction has a track record of durability and they are very lightweight. A modified GWACS Armory CAV-15 lower is central to my Sub 6 with a Twist build. I recently emailed them to ask if they ever considered making a lighter pivot pin set (the ones I have are solid steel). GWACS Armory response was something like… “Yeah… we already make those.” Their real response was much more polite than that but they probably felt like being snarky to the guy who was giving them ideas for products that they already make.
The new lightweight pins save .4 oz versus the standard steel pins. The steel pins weigh .6 oz while the new lightweight pins weigh in at just .2 oz. They are machined from 6061-T6 aluminum and hard anodized for durability. GWACS Armory sells them for $15 including shipping.
Note: These pins are for use with the CAV-15 lower receiver only. They will not work with standard lowers.