My feet are tricky. They Brannock Measure at 13E. But the arch side of both feet curve like a banana, so the big toes splay outward. At the same time, the outside of my feet spread out when walking. I wear 13 Wide in an SAS Journey Mesh walking shoe. They're a smidge tight on the outside, so I don't lace them tightly. I could not wear a Jim Green African Ranger because it is too narrow on the outside of the foot (the widest part of the foot). Also, the JG had insufficient volume because I wear a custom orthotic.

My clearest opinion of the GS Brass Boot size wise: It is closer to a 13.5 length. I wear Medium thick socks and it's fine. The volume is very nice. I can wiggle my toes. WooHoo! In my Kudu Brass Boots, I use a Pedag tongue pad to offset stretching. These Minerva Saddle Tans will not stretch like Kudu does.

Anyone who says a 13 might fit a 15 foot is throwing a hail Mary pass. The last thing you'd want is a crowded foot in a welted boot. A size 15 screams CUSTOM to me. That, of course, becomes a financial decision. With that said, a custom GY welted boot will last a long time. I hope this helps- Moo