Benny
There is nothing wrong with a fixed 4X. I shot a javilena at 412 yards with a 308 and a fixed 4X, the day before my buddy shot one at 328 yards with the same rifle, both shots lazered with a range finder.

One of the guns I have hunted the most with is my 9,3 Chapuis. In 3 trips to Africa and for several years here in the states I have used it with a 1.5-6x scope. I have taken most of my shots with it set on @3.5 to 5X. One or two were taken at 1.5x and several at 6x.

I do like a variable because you can set it on low power in case you jump up something, or something is runnin at you, ie DG. I also like to be able to power up when making a precision shot, or when shooting "herd" animals like turkey, pigs, deer elk etc. When the animals are milling about it is easier to fine the one you want to shoot with a little more magnification, even if they are only 30 [thirty]yards away.

While a 4x will do fine for a light weight 7x57 I would fine a small 3x9 with a 1" tube. I have a Ziess 3x9 on my little Blaser K 95 Stutzen in 308. Works perfect and is ot too big, not much longer than a normal 4x.

I think Kahles still makes a real small 2-7x that would be a good choice as well.