quad rail question

[ronsnighttrain]

I have a S&W M&P 15 sport with a 16 inch barrel and a 7 inch plastic hand guard and A2 style front site/gas block. I am looking to put optics on this.My question is if I get a 9 inch quad rail with low profile gas block,would the rail hide the gas block? Going by my measurements from the barrel nut to the front of the gas block 9 inches should do it. But I have seen a few youtube videos with a similar setup as mine and they still have the tall front sight attached. I just want to make sure so I dont order the wrong thing.

 

[strider007]

If you get a low profile gas block to replace your FSB, you should be fine with a 9" quad rail. Basically, what you are doing is using a mid-length quad rail on your carbine length rifle...this set up will hide the gas block. The only thing that you should do before ordering anything is you should make sure that the low profile gas block you will be using will allow proper clearance for the quad rail you are interested in. Take for example the Daniel Defence RIS II rails...these rails require the use of the MK12 gas block in order for them to be used on the rifle. They are a slimmer rail handguard, so a standard low profile gas block will not work properly...the smaller MK12 block is needed. Also, be sure to get the proper diameter gas block for your barrel...0.750" is pretty much standard, but there are also smaller ones, since some manufacturers offer thinner, light weight barrels. Measure the OD of your barrel where the gas block will be installed, and this will give you your required measurement. Good luck...

 

[superbad]

I dont like after market low profile blocks with set screws, i cut down the fron iron sight and reshape to fit the rail. Never have it touching the rail as that defeats the purpose of free floating although some will argue that an ar can never truly be free floated due to the gas tube. Ive seen a low profile block come off but ive never seen the standard iron front sight go anywhere. Its so sturdy that even after taking the pins out you need to hammer the #### out of it to get it out. You can grind them to as to even fit a troy alpha rail with 4 mm clearance on all sides. A lil gun mrtal black paint to hide the work under the rail and bingo bango that this isnt going no where.