I just bought a pair of KAC M4 RAS handguards for my AR-15 and the top doesent seem to sit all the way down.  Is the M4 more oval or am I just putting this amazingly simple looking accessory on wrong?

Thanks,
BJohnson

more oval

Do you mean the difference between KAC and COLT M4 handguards?

The difference between AR-15 handguards and those of an M4.

Quoted: The difference between AR-15 handguards and those of an M4.

Gregory_K was right--the M4 handguards are oval shaped.

Since I could not understand if you wanted a comparison between a regular handguard, an M4 handguard or a Knights RAS .... let me just state the following:

AR15 handguards or the regular carbine handguards (CAR) are much narrower compared to an M4 guard. The M4's are bulkier, more oval and have (most of the time) double heat shields.

The RAS may be more in the dimensions of a regular AR15 / CAR handguard. But when you add on its panels, they do become "thicker".

IMO


[ETA: BTW what exactly was the problem with the upper part of your RAS? Were you refering to the RAS II or a RIS]

M4 handgaurds are larger on the outside but they are the same dimensions underneath and M4 and AR handguards can easily be swapped on teh same rifle.  If you KAC handguards don't fit then either you're not installing them correctly or there's something wrong with your barrel.