Also, if you're going with the 18.5" barrel, be sure to have a neutered (no bayonet lug) Flash Suppressor. If not, you may not be able to remove the gas plug & you definitely won't be able to remove the gas piston without removing the FS every time to clean the piston.
You could also do what a lot of carbine owners do, get an SEI Gas Lock Front Sight and Direct Connect Flash Suppressor. By doing that, you won't need to use the castle nut or castle nut set screw. I got the FS from Brownells, they have free shipping on orders over $75 until Sun, use Coupon Code:FBA
There are two different types of SEI GLFS you could use. One is hooded & has an elevation adjustable front sight post. The other uses dovetails of two different heights, the one for 18.5" barrels have a higher base & will allow you to use standard M14 front sights instead of having to buy the ones specifically made for 18.5" barrels. Hope this helps!
A forum community dedicated to M14 and M1A Rifle owners and enthusiasts. Come join the discussion about optics, ammunition, gunsmithing, styles, reviews, accessories, Modern, Devine, SOCOM, EBR, classifieds, and more!