Here is the scope mount I have on my M305. It is made in Canada and mounts on the rear sight base. Solid and easy to install. I have a Bushnell 3x9 scope. Good setup for the distances you describe.

JAB

EDIT... here is the link.. sorry... http://www.m14.ca/M14_M1A_CASM_Scope_Mount.html

I don't see a pic or link describing the scope mount, but since its made in canada I get the feeling your talking about the mount from M14.ca ? Thats the mount I am thinking about buying because they have the hole drilled through it for using back up sights for close ranges.

The M14.ca mount is the only one I know that replaces the rear sight.
One of mine has a Leopold 4-10 VX3 on a Promag mount.
The other has a 2-7 LER Hi-Lux scout scope on a UTG rail. Both are used from 25 to 150 yards.
Biggest problem to co-witness is height. Get a good cheek weld on a scope and the irons are way too low. Scopes seem to be much better than they used to be as well, no so much a point of failure anymore.

"I recently purchased a new Norinco M14 shorty. Looking for some ideas on what kind and magnification other M14 owners are using ? I already own a CZ858 that is my cqb rifle which is my go to gun if shtf and I needed a close range rifle for 0-200 yards. I want to set up my new M14 for longer ranges, around 50-400 yards. I used to own another M14 (sold it a couple years ago) that had a ARMS#18 mount with a bushnell tactical mil dot 10x fixed scope. I liked that set up, but I could'nt use the iron sights for close range shots, and 10x magnification was too powerful for 50-75 yard shots."

http://www.marstar.ca/dynamic/product.jsp?productid=75867

Just a quick suggestion, you said under 400$ and this scope is pretty much half that with the 3-9 variable zoom you can still get those 400yrd shots and still tune it back for those 50-100yrd shots.

Standard M14's are hard on scopes. I doubt a cheap one would last unless you have a muzzle brake. I put a brake on both of mine, makes shooting much nicer. No big deal for a few rounds but when you get to 100 or so it can start to leave a mark.

Hello Blueflash.
The mount JAB suggested is a real good one but does require taking the rear sight off, I mounted one on a friend’s M14 and was impressed with it. The scope I put on his doesn’t fit what you are asking for, however I have a solution for you.
http://www.opticsplanet.com/millet-tactical-riflescope.html
This is a tough scope with good glass and the turrets are returnable. It is not a high end scope but is not junk either. I have a 6-25 Millet on my 222 and have also used it on a 25-06 and am very happy.
There are other models with similar options within your budget and it may take some shopping to find the one that works for you. I suggest not buying off the internet unless you have had the scope you like in your hands to look through first.
4 power is good enough for many low light situations especially with the illuminated option. Also with practice the illumination on 4 power can be used as a close range battle sight out to about 75 yards on an 18 inch target. It isn’t perfect but it might work for you if you are willing to give it a shot. Mount this on a .22LR and practice then try it on the M14.
16 power will give you the magnification you need for some decent longer range shots. I had a more expensive 3-12 on mine and danced at 800 yards regularly with hand loads and practice. I am lucky to have a lot of long range experience but again it all takes practice.
If you would like to also have a true battle site backup on this rifle I can make suggestions for that too.

This is one of my gopher guns. A 17HMR semi-auto with an 8-32X44 Tasco ($180.00 but I would not put this on an M14) with a Bushnell red dot mounted above using a setup I built myself with 2 sets of spare rings and a modified base piece (whole addition to scope $160.00 as you see it). Screaming fun at all ranges.
Anything under 100 yards is red dot land… anything from 100- 350 is Tasco land…
I have used similar rigs on my M14, 10/22, 30-30 lever and have built for other peoples M14’s, AR-15’s etc. Using aluminum rings this does not add a bunch of extra weight or ruin the balance.

That Millet scope is actually one that I was thinking about getting. I heard that they are designed for light recoil rifles, so I have been looking for some input from someone with one on a M14 to see how it holds up.

In my opinion the Millet scopes are very durable products. Maybe other folks have had different experiences with them, but I think this would be a fine scope on the M14 for the price point you are trying to stay in.
As far as them being for light recoil rifles Millet does make scopes for this as do all companies, but if you go with a Tactical style scope like the TRS or LRS models it will be a great choice.
I went with the LRS model with a 30mm tube. This way there are more selections when it comes to rings and additions such as levels, cant devices, attachment rings, Ballistic charts and other helpful items that don't fit 35mm tubes.

this setup came with my m14 and I can still use the battle sight with no difficulty. Item#M1401 AIM sports inc. pic file is too big apparently leave a message for me and I'll email it to you cheers