It will not fit without modification. The non-standard design of the fixed front sight on the Ruger AR-556 is not compatible with the VISM extended handguard without modification.
Yes, it should.
Yes, it will.
If uses a 2 piece drop in handguard that uses a round endcap as well as a carbine length gas system it should fit.
If your rifle uses a 2 piece drop in handguard that uses a round endcap as well as a carbine length gas system it should fit.
It will not fit inside the handguard as at it's narrowest it is 1.4". If your barrel extends past the handguard it will fit.
Yes, this handguard is compatible with M&P-15 rifles that have a carbine length gas system, as long as the rifle has a delta ring and front handguard cap installed, or you install those first.
This handguard is built for carbine length gas systems with a MIL-SPEC barrel nut, delta ring, and front handguard cap, so it will fit a 16 inch barrel as long as your rifle uses a carbine length gas system with those components.
The VISM AR15 M-LOK Carbine Handguard will be compatible with M&P-15 rifle models that feature a carbine length gas system. If your rifle does not have a delta ring or front handguard cap, you must first install those in order to install this handguard.
Yes, the VISM AR15 M-LOK Carbine Handguard will be compatible with a PSA 16" M4 that uses a carbine length gas system and front sight post with a delta ring.