This MDT .300 WM magazine can be used for 7mm mag, 30-06 and 6.5x55 calibers. In some cases the feed lips may need to be bent. Maximum cartridge OAL that will fit is 3.625".
Are these magazines compatible with the 300 prc
No sir, you'll need this magazine https://mdttac.com/300prc-mdt-metal-aics-magazine/
Will these work with factory loads. 28 nosler 162 gr hornady precision hunter.
I believer you will want this magazine in .338 LM with 3.850" length. https://mdttac.com/us_en/mdt-metal-magazines-long-action.html. I would double check and ask MDT themselves about your .28 nosler just to be sure.
Great product, glad I went with Grayboe!