My son who just returned from Afganland has a TLR1 on his M4. That rifle had a Knights Armorment forearm, and he mounted his forwrd on the right side of the rifle so that his left index finger could activate the light (he didn't use a verticle fore grip). Worked fine for him, an he will now mount it on his personal M4'gery.
Enfield .303 Accumulator/Collector
Proud Father of Two US Army Soldiers