Best Handguard to barrel ratio?

I'm putting together my first build with a 10.5inch 300 Blackout barrel. I'm used to shooting the slightly longer 14.5inch barrels out of M4s so I wanted to give this one as much handguard as I could so I can have a comfortable pull. Since the last half inch of the barrel is all thread and some amount goes into the upper receiver, would a 10" handguard not give me enough room to properly fix a muzzle break or can on it? I know different handguards and barrels can differ but I was wondering if there's a common consensus about how much room you want to give the end of the barrel.


IMO the only way to know for sure is to dry fit the parts. Not all hand guards have the same inner diameter and thus will give different clearances. You can use the builder app at and if part won't work it won't allow you to add them. I'd consider going to a LGS that builds AR's and see if they can help you figure out your part's list. In my area I have found that Curt's on McLoughlin is pretty friendly and accommodating.

To accommodate a shorter hand guard consider an AFG. They are legal for an AR-15 pistol if that's what you are building. If it's an SBR then either a VG or an AFG will help to straighten out your wrist compared to just the hand guard.


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