The terrific chart that KevinB posted on the AR Discussions:
http://appliedinc.com/railsys8.gif

I'm wondering if my calculations are approximately correct.

1 pound (Lb)=16 ounces (oz)

First Samco said that their RIS handguards will not noticeably change the weight of the rifle. They are listed between 8.5 and 9 oz.  Thus, the standard Bushmaster carbine handguards weigh approximately 8 oz.

Bushmaster Superlite Telestock: 6.25 Lb
Bushmaster XM15 E2S A2: 7.22-7.33 Lb so about 7.25 LB
Bushmaster XM15 E2S A3: 6.7 LB
Thus the carry handle weighs about .5 Lb.

ARMS SIR #51: 21 oz   Subtracting the weight of the standard handguards (21 - 8) =13 oz, which is about .75 Lb. Put that on the Superlite A2 and it comes out to 7 Lb, still lighter than the majority of A2 carbines, correct?

ARMS SIR #50C Bilevel: 16 oz or 1 Lb.  On the Superlite A3, subtract .5 Lb for the lack of carry handle (6.25 Lb - .5 Lb) =5.75 oz, then subtract 8 oz from the SIR to compensate for the other handguard (16 oz - 8 oz) =8 oz or .5 Lb. This comes out to 6.25 Lb, the original weight of the Superlite A2.

I can see how one of the heavier SIRs might cause weight issues with many AR carbines (unless one is bench firing all the time), but do you guys think that there's much to be concerned about with putting a SIR, particularly a #51 on a Superlite?

Sounds like a good compromise/tradeoff and you end up w/ an ideal combo.

Just a quick note, the Fobus HG are indeed vented.

By Jove, he's right!  Sure looks vented to me.
[img]http://www.blackrifles.com/samco/m44s.jpg[/img]

If you want it light, don't go SIR.  The rail weight is only the start of the weight gain because then we all like to hang all the goodies on.

We wanted to have four rails with NO weight gain over std HG's and we came very close to having our cake and eating it too.  Our 7.0 Rail at 8.5 oz complete still outsells every other rail we produce!

southern
[url]www.danieldefense.com[/url]

The Forbus has (plastic) rails that are way out of spec and absolutely usless for anything but a flashlight. They attach to the barrel and flex from the slightest amount of pressure.
Jack

So that's where the Daniel Defense 7.0 comes in, as was mentioned.  $100 cheaper than a SIR, too!
What sorts of experiences have people had with the 7.0?  

For mounting, it says "disassemble barrel." Concerning proper forum conduct, should I ask about that here or just email DD?

3rdtk, the fobus is NOT designed to take optics.

And disassembly means drifting the taper pins, removing the FH/comp, and removing the FS.  Then you will have to remove the barrel nut and delta ring.  You need some tools for that one.  HTH.