i have a regular set of CAR handguards on my bushy m4 i was wondering if there is a substantial difference between m4 handguards and CAR ones. thanks

If your talking between CAR and M4 Handguards. Yes the M4 HG's are fatter . A big difference if you have small hands.

i mean is one set sturdier or anything like that?

The M4's don't have a taper, and are about the same size, as the fat end of A2 rifle handguards, perhaps a little fatter.

how many cooling holes do new m4 handguards have? the CAR handguards have 7...and whats a taper(yes im a retard)

M4 handguards are about 1/8" wider and are taller as well.  The ones made by Colt seem to be made from a stiffer plastic and have double heatsheilds that are held in place permanently with what looks like an epoxy glue.  They have 7 cooling vents, but due to the double heatsheild design, you cannot see the barrel thru the vents.  (This complicates the install of rails I have heard)

Their main advantage with the M4 guards IMHO is the heat sheilds.  With standard carbine guards, your palms are farely close to the barrel, and with only one thin sheet metal sheild, the heat off the barrel can get uncomfortable fast!  With M4 guards you can fire rapidly for much longer time before barrel heat reaches your palm.

BTW, they do have a very slight taper (inward slant from the very top and bottom surfaces.)

Tex78

hmm that complicates things...i want to mount a harris bipod to the handguard.if i go m4 gaurds does that mean that ill have to drill through the heatshields?

Ironclad, my M4 handguards have little dollops of glue holding the heatshields in where they go into the little grooves...very easy to break those, and remove the heatshields.  

You can install a bipod adaptor on the bottom handguard, or a picattiny rail, then just reinstall the heat shields.  I didn't even glue mine back in, and I've never had any trouble with them coming loose.  

Fenian is correct a little down ward pressure with a sharp point and a push with the point in the tab that has the glue on it towards the center on the handguard and the tab will slip right out and if care if taken the tabs will return to the original position .