What's the difference between these two? Why are they $100 difference?

http://swfa.com/SWFA-SS-10x42M-Tactical-Riflescope-P53713.aspx

http://swfa.com/SWFA-SS-10x42-Tactical-Riflescope-P53712.aspx

Side focus is more expensive to build. The $299 models all have rear focus. If you need to dial quickly for distance, the side focus is handy. If you're not on the clock, either works just fine.

Maybe the side focus on the "M" but I'm not sure

Thanks for the help y'all. I ended up talking to my FIL this Thanksgiving and he has an old Japan made 6-40x40 tasco tactical scope he doesn't use. He said I can use it:) if it doesn't work well then I'll be back looking since SWFA deal will be gone. They have some great deals. Midway has some great deals also.

For a thousand yards, you might as well buy an SS that's on sale today. Doubt that scope he gave you is going to be as enjoyable to shoot with.

I had a Tasco 6-24 for a few years. It was far from being a great scope, but was Ok in daylight. It was very dim in low light.

I'll vote with Fireman and the others and suggest that the OP get the Vortex he can afford. If a fellow spends $300 or more on a scope with a poor warranty, and the scope breaks, that $300 is essentially gone. Buy the Vortex (or a Leupold), and if it breaks, your total cost is going to be just the shipping cost to Vortex. As an example, I bought a used Leupold fixed 6 power about 35 years ago, later sold it to my youngest brother, who brought rifle and scope to me on Thanksgiving to sight in. The scope had broken internals that were loose and rattling around. If it wasn't a 'good warranty' scope, I'd just toss it in the trash, but I'll send it to Leupold and they'll make it good as new and send it back. I suppose you could make the case that a Vortex or Leupold is a lifetime purchase. Buy it once and own it for life, or at least till you see the flashy new scope that your buddy just got, which causes you to upgrade.