What kind of help? What are we looking at? All I'm seeing is an outline. Flash may help with the some detail in the picture. Manufacturer of the hand guard? Upper? How specifically doesn't it fit?
kind of looks like an AR mag well and take down pin...looks like a flush cup that ain't so flush. Where are you measuring from? Are those screw holes that allow the rail to attach to the hand guard?
what length are you trying to buy? you can go all the way to the end of the barrel. I would also say do not get a quad rail but one that accepts attached rails where you need them
what length are you trying to buy? you can go all the way to the end of the barrel. I would also say do not get a quad rail but one that accepts attached rails where you need them
No sir it can be as long as your barrel and as short as you have it. a QUAD rail has the rails on all 4 sides(very uncomfortable) any free float handguard will work and th Keylock or Mloc ones are where you can add rails where you need them.
Generally speaking
a carbine hand guard is about 7" long leaving the M4 style front sight exposed if it so equipped
a mid-length hand guard is about 9" and would cover a low profile gas block on a carbine.
rifle length is about 12" and give you the look like FrankT upper 2 examples
from looking at the picture you posted it looks like a carbine length barrel with a grenade launcher cut in it in front of your hand guard. It also looks like you may have a low profile gas block installed because your hand guard covers it and to do that it would need to be a mid-length to give you the flat top all the way out.