Would anyone have one that would hold 300 Winchester. If so could you please tell me its measurements. LxWxH

https://www.midwayusa.com/product/1564131668

Another approach is to go to the link you provided, click on the "Q&A" tab on the right side scrolled down a bit, and type your specific question there. You may get a quicker answer there.

http://www.mtmcase-gard.com/products/rifle/ammo-boxes-rifle-r-100-deluxe.php

Click on sizes, bottom has outside dimensions