Recipe formulation

Hi All,
If I take a recipe say from Brew 250 or BYO magazine, and input it into BeerSmith I get a big variation on estimated OG, SRM, and to some degree IBU. I do go into BeerSmith (2.0) and adjust grains, hops, and etc. I use a 65% efficiency rate in the program as well, as most recipes are laid out for 65% efficiency. So when I get done adjusting for the above the grain bill is somewhat altered as well. I do all grain and I'm wondering why the differences in those vital stats. Also, when adding lactose the program doesn't allow you to input the time to add it to the boil. Please excuse me if I'm wrong on that one. Any information would be appreciated.
Thanks all - Great Forum
Simie

I can't remember specifics, but somewhere in the front of each BYO magazine is a table that gives their assumptions to efficiency, etc.  I'm also curious regarding this as I seem to have similar issues when copying recipes in.

The magazine efficiencies are usually stated at 65%. I know estimated gravity is just that, but I would think the values to be close. I put in a stout recipe yesterday and I got a SRM value of 38, when the recipe said it should be 49. That's a pretty big difference. I know there's a good explanation, I'm just curious. Same thing happened to a Porter I made last week.
Thanks. all

I just came across the Lactose issue not allowing you to choose when to add it to the boil. I was working on a Sweet Stout recipe this morning and I went back to double check it because I thought I missed something.