Kenneth, the AR-12 (MKA-1919) Style 20rd and 15rd Drums will work in the HDM Bull pup. The only caveat is that the 20rd Drum will have your shoulder at an un-natural chicken wing angle due to the width in the HDM Bull Pup. budsgunshop.com/product_info.php/products_id/714025798/promag+mka+1919+12ga+2.75+15rd+drum ---------------------------------- budsgunshop.com/product_info.php/products_id/111608/promag+mkaa1+akdal+12+gauge+mka+1919+2.75+20rd+black+drum ------------- Cheers and stay safe!

Kenneth, no magazine specified. If you post again with the model number or upc we can help you, you can find the model number and upc under the products description. The HDM Bull pup and the 1050 protector uses ar12 style magazines and mka 1919 style magazines/drums. If interested here's a link to a 10 round magazine that will fit................. budsgunshop.com/product_info.php/products_id/411559964/sds+imports+turkish+ar12+12ga+10rd+magazine................... And here's a link to a 15 round drum magazine if interested................. budsgunshop.com/product_info.php/products_id/714025798/promag+mka+1919+12ga+2.75+15rd+drum................ And lastly here's a 20 round drum that will fit.................... budsgunshop.com/product_info.php/products_id/111608/promag+mkaa1+akdal+12+gauge+mka+1919+2.75+20rd+black+drum................. Hope this helps.