A1 models were lighter because of pencil-thin barrels, fixed stock, lighter handguard. A3 should be at 3.4kg while A1 cca 2.9kg

"M16A3" as issued to Israeli army marksmen was just a standard A2 with safe-semi-full auto modes (it had a permament carry handle, not flattop, regular "govt" profile barrel) thus it should weigh same as standard A2. It was marked M16A2E3 on the receiver. 

zragon13 said:

It was marked M16A2E3 on the receiver. 

That's interesting.  Who manufactured your A3's?

I'm pretty sure that they were Colt and had US Govt stamped on receiiver although the A3's that were issued beginning in the mid 90s as DMRs were all brand new (not second hand from US like the M16A1s). They were replaced in my unit by M4s after Lebanon2 and those were replaced by Tavors around 2013. I've seen issued M16A1 and "M4s" built on A1 lowers that said H&R or GM Hydromatics, but IIRC,  all the A3s were Colt. 
 

If it's important to you, I can look for old photos of receiver markings that I took.

It's not particularly important, I was just curious.  Thanks for the reply.