What can you tell me about this upper?

[rhuff]

Originally Posted by cneider

This is some good information. So, to err on the side of caution, I should install a 9mm mainspring like this one http://www.gunpartscorp.com/Products/465390.htm Worst case scenario, it may not cycle .30 Luger ammo, but won't do any harm either. I always try to load to "Factory duplication" specs in my Lyman, FWIW.

I don't know what poundage that spring actually is. I purchased my springs from Wolff Springs, and they will tell you what the std. spring weight is, and also offer a mainspring that is two(2) pounds lighter.