BudsGunShop.com - Rifling and Magazines

Wayne, Yes. The 18" barrel has the Armornite® Finish on Barrel (Interior & Exterior) and 5R rifling. And yes this sporting rifle will take 20 and 30 round AR10 magazines and AR10 .308/7.62 NATO drum magazines if you can find them. Armornite® Finish on Barrel (Interior & Exterior) is S&W's trademarked melonite treatment.

Wayne, yes Sir it has both. The rifle will also accept any SR-25 Pattern Magazine and Drum. Cheers and stay safe! https://gun.deals/search/apachesolr_search/840815121978

Yes sir 5r rifling indeed copy and paste from SW info page
"Engineered with 5R Rifling and 1/10 Twist, the M&P10 is as accurate as it is powerful. Making short work of long range, M&P10 Rifles keep you at the ready." "Features
• Ambidextrous Magazine Catch, Bolt Catch
• Ambidextrous Safety Selector
• Patented S&W Enhanced Flash Suppressor
• Gas Block with Integral Picatinny-Style Rail
• Sling Swivel
• 5R Rifling
• Armornite® Barrel Finish
• 9310 steel bolt
• Chromed Firing Pin
• Optics Ready"
And as for available mags.
There are other mags out there but I'd stick to these brands or at least research and other brands, these have all been really reliable for me though.
Buds has Magpul 50rd Drum mags in stock.
budsgunshop.com/mobile/product/714020538/magpul+pmag+d-50+762x51+lr%2fsr+blk />And Lancer 20rd
budsgunshop.com/mobile/product/36554/mag+lancer+l7awm+762+20rd+trans+smk />And in black 25rd
budsgunshop.com/mobile/product/711019276/l7+advanced+warfighter+magazines+-+l7awm+762mm%2f308+caliber+opaque+black+25+round />25rd lancer FDE
budsgunshop.com/mobile/product/713081591/lancer+magazine+l7awm+sr-25 />25 rd FDE Hexmag
budsgunshop.com/mobile/product/713081509/hexmag+magazine+sr-25+308+win />