Sounds too tight to me.

The distance around my shoulders is also about 50" and my 60" Feathered Friends Swallow bag is too tight for me.

Having a bag that is too tight isn't just uncomfortable, it reduces the bag's warmth too. When my arms and shoulders press outward it creates cold spots.

I switched to a Montbell stretchable bag and it works better for me. Plenty of room but still warm and light.