My thoughts about building a 6.5 AR were derailed on Saturday because I wondered across a SIg 556 R at the Fun Show.. The rifle came with the Sg Red Dot , which I don't see my self keeping.  This will; be a Range Toy or an Occasional Bambi blaster so I am thinking a moderately priced 1-4  any recommendations for mounts would be helpful. Also forearm has a bit of rattle  , any thoughts beyond shimming it?

I shimmed mine with preformed high temp silicon pipe sealant from Home Depot.  

Also, if you are annoyed by receiver play, buy or build a Zurich Wedge.

Vortex 1-4? LaRue/Bobro/ADM?

The lowest rings you can get and still mount the scope.  What I did with mine.

I've been contemplating shimming my handguards, but I'm not sure I'll be keeping my 556R  Accuracy isn't really living up to what I want, it's shrunk a bit since I've been shooting it so possibly I'm adjusting to it, but it isn't outshooting my AK's yet.

I have two Millet 1-4 DMS Scopes in ARMS rings. I like them a lot. One is on my 556R (low rings) the other a FS2000 (med rings). PM if you are interested in taking a look at my setup.

The one on the FS2000 is for sale because the FS2000 is for sale. Planning on replacing it with a 556 XI Russian pistol.

I put an Optisan 1-4 Mamba in an SWFA mount on my 556r swat. Perfect scope for this gun, tracks well, maintains zero and about as cheap as it can get at about 150 including the mount.

Low-priced 'SIGARMS' CP-4 (4X, illuminated reticle) on 556R(2). BTW, don't dismiss the 'SIGARMS' Micro red-dot. Its well made and shoots great. I put the one that came with mine on my AMD65 with a Strike AK2 rail that moves it to the rear some and drops it just over the action cover. I roughed it in with a cartridge laser, took it to the range and zeroed at 25 yds 1" low. Moving to the 50 yd range, I fired one shot and hit the bull's eye - done. That's also a 100 yd zero but I haven't taken it back to make adjustments at 100. Anyway, it seems to be a good, small lightweight optic.
Back to the CP-4. What can I say? I put it on, roughed it in at home with the chamber laser, adjusted at 25 yds 1" low, moved to the 100 yd range and zeroed. I am using only Golden Tiger in both guns and this stuff shoots great for imported steel-case - I got 1.5" at 100 that first time, and that was with an improvised rest because I left my damn sand bags at home, and I haven't been back with it yet. The scope is not quite as clear as my $1000 ACOG, but its very usable. Illuminated red and green reticles have several brightness levels but really I just leave it off and use the black reticle. The reticle is interesting - basically a plex but it has a small dot at the center along with 'man-height' ranging marks across the bottom and bullet drop lines on the vertical. I believe the BD lines are based on the 5.56mm so they're just suggestions with 7.62x39. :) Once I got used to the dot at the center, I started looking for it when I picked up another rifle without that. So, its a small integral-base scope that has decent glass for the price and works great. The wired-on turret covers are a nice touch and it came with flip-up covers too. Also has adjustable eye-piece with a brake on it so it will not shoot loose.
Don't worry about the rattles - just forget about it and shoot the thing.

+1 on the Golden Tiger. It is the only variant of the Wolf family that my rifles can group well with.

I run a PFI RR-Evo 1-4x on mine. Great budget FFP scope, and I like that you can mount it low. Only downside is that the fixed iron sight really gets in the way... I need to grab the MFI folding sight or something.