A number of honest reviews are posted at
http://www.chuckhawks.com/index2d.rifles.htm and specific recommendations are made in this article
http://www.chuckhawks.com/recommended_muzzleloaders.htm
There are a few I would add to that list depending on the spending level. If he must use a scope, you should certainly take ease of scope mounting into consideration. The 320 Austin & Halleck can be had right in that price range (see D&R Sports at
http://64.224.40.78/miva/merchant.mv ).