Yea the older one is more like the 10/22. The new 99/44 is bases on the mini-14 Here's part of an article on it.

The Deerfield Carbine is based on the Ranch Rifle design but uses a four round rotary magazine instead of the staggered box magazine of the Ranch rifle and Mini-14 rifles. The reason for this special magazine is the .44 Magnum's rimmed case.

Heres the rest of the article

http://www.chuckhawks.com/ruger_deerfield.htm