You can legally purchase this in MD ; budsgunshop.com/catalog/product_info.php/products_id/34869/Ruger+AR+223+Rem+%7C+5.56+NATO+16in+10Rd

Bud's Item Number: 34869

Type "MD compliant" in the search window and it will show you multiple AR rifles that are legal for you to buy.

No: Certain models of firearms are banned as assault pistols and assault long guns. It is illegal to possess an assault weapon or a copycat weapon with two or more specified features (folding/telescoping stock, grenade/flare launcher, flash suppressor) unless owned before 10/1/2013, or received through inheritance from a lawful possessor and not otherwise forbidden to possess.-------------------------------------------------------------It is illegal to purchase, sell or manufacture magazines with a capacity of greater than 10 rounds within Maryland. However, possession of magazines greater than 10 rounds is legal if purchased out of state. These may not, however, be transferred to a subsequent owner unless done so outside the state of Maryland.

No, the magazine capacity needs to be limited to 20rds.