This is a discussion on Scope mounts within the The M14 forums, part of the M14 M1A Forum category; I'm think about getting a scope mount but a lot of reviews say they are mot stable enough. Different brands all have about half bad ...
Do you want it to be permanent or do you want to take it on and off? I use a Bassett and have had good luck with it. I put the scope on to deer hunt and take it off to shoot my irons. On and off in 20 seconds.
I like my Fulton DMR mount a lot. Rock solid, uses the speed clip dovetail as part of the fit to the receiver. The underside of the rail is undercut, you can use your iron sights with the mount in place (scope removed) out to about 400 yards.
As stated above;
It all depends on your desired use
If you plan to leave the Mount installed for most of your use, then the one of the Sadlak Mounts are your best bet
If you are looking to install it and remove it over and over, and / or use your Iron Sight too, then the Bassett Mount is by far your best Mount for these applications
The Bassett High Picatinny Mount will allow the use of the Iron Sight while the Mount is in place
Or any of the Bassett Mounts can be removed and reinstalled very easily and will always return to Zero, over and over
I use the m14.ca Casm gen 2. It replaces the rear sight pocket and is meant to stay on. Between this and the basset i can say that the casm is def. more secure and more fixed to your rifle. The only down side is what other users have stated in that the rear sight is taken off and you cant quickly take off the mount and shoot irons. I don't care for this. I use a vortex sparc 2 red dot for the range and hunting but also can throw on a scope for longer shots. I had my fun with the irons but now use the rifle almost every weekend for hunting and find myself never needing the irons so the fixed mount works for the job my rifle has. All this being said the Basset works great and you can keep and hold zero with no problems all while being able to take it off real quick. IMO it allll comes down to how you want it to look. I hate the basset style side mount look.
I run Sadlak titanium mounts on both my M1As. They are meant to be permanent mounts. No problems with the installation. With that said, both my National Match and Supermatch receivers are in spec. Any of the Sadlak mounts will do, just find the one that fits your budget.
The best M1A/M14 mount out there (if you can find one - and if you can live with the 26mm built in ring limitation) is the IDF M21 side mount, It has a spring loaded plunger in the locking knob that engages serrations in the mount (under the knob) - so that when you tighten it is stays tightened.
The only issue that you need an in spec rifle with the barrel at a true right angle to the receiver as the only adjustments to the point of aim are internal to the scope.
My Bassett works for what I use it for ,I have the Basset mount with a Leupold vx3i 3.5-10x 40 mm so it's not a heavy tactical scope and I went with their regular height picatinny and I can use irons with s ope mounted plus on and off in just seconds with little if any loss of zero IF you use correct and exacting method of instal.