Would plasic/nylon tactical rails hold up well in comparison to aluminum?  I ask this because the price difference is about 4X as much for aluminum.  Anyone have any experiences with nylon/plastic tac rails?  TIA

i stick with the aluminum rail

There is no dimentional integrity to plastic rails, tey are just shot of of a mold like crap thru a goose. Onec you start to tighten anything to plastic dovetails they just crush.
If you want the best of both worlds, I'd suggest the SIR system for cooling, and alum rails when and where you decide to use them.
Good shootin, Jack

Boy that's the truth. I have a tactical light rail (streamlight) made out of that black plastic, it is a major workout to get FAS2 mounts on and off that thing, have to brace the handguard on the floor and pull like the dickens. good thing it was only $14...go aluminum if you can.

Personally speaking....

Stick with aluminum.  I just cannot trust plastic to hold something on, or hold something together, on a carbine...

YMMV

Monty

Say what?  The FAS2 sure works good on the plastic rails, takes me a moment and no effort to attach and remove, it's QD after all.

If you are not going to mount anything critical on your handguard, and you are not going to really be torquing on it, I don't see a problem with inexpensive rails.  I have expensive aluminum rails on 4 out of 5 rifles, but the 5th has plastic, and it is plenty good for what I use it for (verticle grip, light, and bipod), though I am not torquing down on it, nor using in combat, just range plinking.  Cost me about $45 (cause I only used half the handguard rail set).  Why pay $300+ if you don't need it?  However, if you plan on mounting any kind of optic, going to be hard on your verticle grip, or plan on upgrading in the future to serious equipment, go with the aluminum.  Everything has it's place.  Not everyone is going to be soldiering around with their rifle, and thus don't need to maintain military standards.  Just get what you need.  Just remember, plastic is no substitute for aluminum, but perhaps you don't need to go to that level.  You get what you pay for.

thanks yall (and to you Mike, you've advised me on quite a few things in the past).  I'll probably go with the nylon rails until I see that they don't fit my needs...then I'll upgrade.  thanks again!