This has probably been covered before, but I was unable to find anything using the search function.  

I am wondering if putting a rail and vertical foregrip on a standard carbine or mid-length handguard would be a problem on a light or government profile barrel.  I understand that it can cause the barrel to "flex", affecting accuracy?  Is this really the case?  Is using a free-float handguard the only option?  Thanks.

You can do it w/o a free float tube (though both my A2 and my Lightweight profiles are now free floated).  The Fobus M33 handguards work well as do the YHM handguards with minimal problems.

I've run 2 carbine courses with the M33 and VFG with no issues.

However I've had issues with the Fobus M44s and VFGs.  While you will maintain enough accuracy at 50 yards and under - you will notice an increase in group size and a shift.  I think this is because the handguards apply pressure to the bottom and one side - thus making the deflection uneven.  For CQB it works - but at longer ranges don't use the VFG with the M44s.

Thanks for the quick response.  I am building a new AR this weekend (only my second) and would like to do what I want right the first time.  I will probably just go with a free float handguard on the new carbine and save myself the time and money in the future.  

i dunno... talk to lumpy he's the one with the vertical grips on the both of his gov. profiles...

i use rasII (FF) so i don't worry...