For carbine hand gaurds I have heard that colt uses a cheaper polymer but has double heat shields,Cav Arms claims a superior polymer but single heat shields,I have the bushmaster M4 type they seem very good quality in my opinion better than the colt,but the colt is the only other set I have,as far as heat the fat M4 take it well I went through 12 mags at 20 to 25 RPM until it got too hot that I went to gloves and it was still very warm,7 mags with the standard size,I know colt and bushy use fiberglass/nylon 43% polymer for full size rifles,and texture and feel to me is the same,so I would say carbine M4 bushy,standard A2 either company and soon Im getting a cav arms M4 handgaurd so ill be able to make a full comparison.Det.carry handles I have no experience with.