FSB, 16" M4 barrel and 9" + handguard

Hello, wondering if I can use my FSB or an ARMS front folding sight gas block on a 16" M4 barrel while utilizing a 9" or 10" free float handguard rail or do I have to have a mid- length barrel?

You would need to go with a 7" rail if you have a carbine length gas system. You can shave the FSB to keep the longer rail system and then go with a rail mounted front sight. Or go with a mid-length barrel.

Thx u sir!

Just to name a few. Troy, Centurion, Midwest Industries, have two piece free float rails with FSB cutouts for M-4 barrels.

https://troyind.com/rail-systems-accessories/rails/two-piece-free-float

http://www.centurionarms.com/product-p/0609-cc.htm

http://www.midwestindustriesinc.com/index.cfm?fuseaction=category.display&category_ID=422

Samson has a one piece extended FF rail.

http://www.samson-mfg.com/mm5/merchant.mvc?Screen=PROD&Store_Code=SM&Product_Code=Evolution-7-EX&Category_Code=PLATFORMS

Thx! Always favored a carbine profile to the longer handguard/ rifle look, though I am considering those like the Troy/Vtac Delta. If not, leaning toward the MI Gen2SS FF 7" or the new Ergo Grips Slim keymod 2piece - any thoughts on the Ergo, haven’t seen much but guessing still new- but pricier than the MI.

The I used to have the Vtac Delta and it felt awesome and was decently light weight.