As you can tell the opinions are about split 50/50, and probably will remain about that through out the comment string. The truth is that either will work fine. I have hunted very little where 300-500 yard shots were even a possibility. Most of my hunting is far tighter than that, with a 200 yard shot being "long". My vote - 3-9x40.

As already mentioned adequate eye relief is critical, as are clarity, a chrisp image and peroirmance in very low light. Buy the best that you can manage. You will not ever regret having done so.

I use 6.5X20X50 or better Leupold. My shots tend to be long, and the greater magnification is perfect when I go prone.

I have mostly 3x9s; one 2x7; and a 1.65x5 on my ML. I like the wider field of view at low magnification. Maybe if you were planning on shooting 400 yards a 4x12 would make sense, but in my opinion, for most situations, I'd go with the 3x9.

I pulled up the specs for the Diamondback models you mentioned. For me neither would be a choice as the eye relief (as some have already mentioned) on both is well under what I would put on any .300mag. FWIW, I happen to own four rifles in .300mag in one form or another. With eye relief as low as 3.1" and 3.3" both those scopes are a no-go for me.

I'd suggest a Leupold VX1 or Rifleman in 3-9x40 instead, for just a bit more $$. They have eye reliefs of no less than 3.7" and up to over 4" depending on what power it is set on.

my leupolds are vx1 or the older vari x 2 scopes.I killed a deer at 495 yards no proplem with a 3-9x40 scope vx1 on a 7mm rem mag. have a 4-12 Leupold on a 35 whelen.

A Minox ZV-3 would run about the same price and has more eye relief.

What about the red field revolution? I've heard pretty good things about them and I think they're made by leupold and have the same eye relief.

As far as eye relief goes is there much of a difference between 3.3" and 3.7"...that's just the distance from the scope your eye can be to see the whole view with no black spots in the scope, correct? Do I need a greater eye relief due to the 300 win mag caliber and it's recoil so I don't smack my eye when I shoot or is that not the reason. Thanks

the redfield revolution is equal to the leupold rifleman. I prefer the vx 1 guide has the vx1 3-9x40 for $199.
http://www.sportsmansguide.com/net/c...p=WX2&i=235375

As far as scopes go I've always been a fan of Leupold, but these days there are many good choices when it comes to optics.

One factor many don't consider when buying a scope is the exit pupil in low light conditions. You can always use a sun shade in bright conditions.

A 40mm objective lens will give you a 13.3 mm exit pupil at 3 power, it's reduced to a 10 mm exit pupil at 4 power.

If you go to a 50mm objective lens at 3 power you will have a 16.6mm exit pupil, and a 12.5 exit pupil at 4 power

The differences in exit pupil can be a huge factor in low light conditions. The average human eye will have a 5 to 7mm pupil in low light conditions. A large exit pupil from your scope is a great advantage.

Exit pupil is just one thing to consider when buying a scope, but IMHO it's one of the main things to consider when making the choice of power, and objective lens.

http://www.shootingtimes.com/2011/01...cpupil_061907/