I understand what sand cuts are and what they do.  My question is why they don't allow the use of an empty mag actuated bolt hold open (or do they?).  Everything that I have read says something to the effect of "the Brits decided that a reliable weapon in the desert was more important than the bolt hold-open."  Is there a cut on the bottom of the bolt that I haven't seen, or is there some other reason that they nixed the hold-open?  I just can't see why it wouldn't work unless the bottom of the bolt was altered.

The no bolt hold-open is a feature in addition to the sand cuts.  The two hae nothing ot do with each other, other than making it more reliable in the sand.  The bolt hold-open is manual only on the L1A1, because they wanted it to stay closed as much as possible to keep sand out.  The Canadian C1A1 does have a last round hold-open.  All the Brit, Aussie, and Canadian rifles are built to the same specs for interchangability.  The only difference is on the L1A1, the pin that the mag follower would hit is shorter.  You can just remove the short pin and put a longer one in and the last round hold-open feature is active.

It has nothing to do with the bolt carrier itself, other than holding it open.  The bolt catch is what's different.  The pin isn't long enough to reach teh mag follower on an empty mag.

During the first field tests of the L1A1 the Brits were heavily engaged in the Aden (Middle East) and found out that sand played hell with semi-autos.  They came up with the various things like sand cuts on the carrier, sand cuts in the receiver, no last round hold-open, etc.  This greatly increased the reliability of the rifle in sand.  

Ross

Thanks Ross, that was exactly what I wanted to know.