While surfing the internet I found a site that manufactures special AR lowers with widened mag wells to accept stock 30 rd grease gun mags. Seems pretty neat. It uses a unaltered .45 acp Olympic Upper. The only catch is the guy who makes them does not have a firearms manufacturer license, so if you want a 100% receiver he has to send it to another company to complete the receiver. Heres some links, pics, and videos.
http://www.cncguns.com/projects/AR45lower.html
http://youtube.com/watch?v=q2IfK4jDQUU
http://youtube.com/watch?v=QUY_8TjV4uE
http://youtube.com/watch?v=Hbxv-FtkS_E
http://www.cncguns.com/projects/AR45lower.html
http://youtube.com/watch?v=q2IfK4jDQUU
http://youtube.com/watch?v=QUY_8TjV4uE
http://youtube.com/watch?v=Hbxv-FtkS_E