Handguard wont fit my AR

[s2thalayer]

I bought a DPMS complete upper from Midway a few days ago. I planned on removing my quad rail system (knights armory company) from my Bushmaster AR and putting it on the DPMS. The DPMS has a bull barrel, the Bushmaster doesnt. The rail just isnt fitting on the DPMS. I cant get it under the gas block or whatever it is. Anyone know if im doing anything wrong or do i need a special quad rail to fit?

Also could i just file this down? Or is that going to create problems?

 

[HiBC]

First thing to do,breath deep,have a cup of coffee,and do not get radical .
It supposed to be fun.A whole lot of the working on guns thing is gaining an education through experience.Take the time to understand how everything fits together.Don't be afraid to call Knights Armament with a question.I have not worked with your forend.
There is a rifle,a carbine,and a mid-length gas system.Your forend should allow the front gasblock/sight to work if you are going from/to the same length.The gasblock will be just forward of the installed forend.It may be necessary to remove the gasblock and gas tube as an assembly,install the forend,and then replace the gasblock.
It may be that the DPMS barrel nut must be removed and the Knights Armament barrel nut installed.I don't know.If that must be done,it requires tools and a real understanding of how to do it.
Good luck!!

 

[s2thalayer]

I'm kind've stumped. With a more descriptive explanation, its definitely the right length. The handguard fits perfectly length wise, snug, but perfectly. the lip under the gas block as about an eighth inch too low for the handguard. I suspect the issue here is the barrel thickness change. i could likely file down my handguard to make it fit, but i dont know that i want to go that route, silly as it sounds, the handguard has some sentimental value as my brother gave it to me before he left for Iraq. After doing some googling, i read a few reviews on the Magpul MOE handguard that say "I own a DPMS bullbarrel and this handguard isnt supposed to fit, but it does", so i ordered it. Hopefully it fits. If not, i have plenty of files (and ill consider removing the gas block like you suggested)