Years ago, AR parts selection was much simpler than it is today. Colt made AR-15s, and you could buy a rifle or carbine. Aftermarket accessories were limited. Fast forward to the present day and things can be confusing to the aspiring rifle builder. Parts selection seems limitless and mistakes can easily be made during assembly. This week we look at handguards, delta rings and handguard caps and explain the options available.
Not every AR needs a fancy free-float handguard sprouting rails. A basic self-defense carbine will be fine with the standard military-style plastic two-piece handguards retained by a spring-loaded ring at the rear and a sheet metal cap at the muzzle end.
Handguard lengths can be broken down into three types: carbine (7-inch), mid-length (9-inch) and rifle (12-inch).
Early (M16A1 era) handguards were triangular and the left and right halves were not interchangeable. They were lined with aluminum heat shields and retained by a spring-loaded slip ring at the rear and a sheet metal triangular cap at the muzzle end directly behind the gas block/front sight base. When the M16A2 was introduced in the 1980s, the new handguards were round and the upper and lower halves were interchangeable and constructed of a tougher ribbed plastic. The rear spring loaded ring was changed to a tapered shape and referred to as a “delta” ring. The triangular front handguard cap remained unchanged except for an increase in the center hole diameter from .625″ to .750″ to accommodate the thicker A2 barrel diameter at the gas block.
Carbines pose another problem. The early handguards were round, 7 inches in length and contained single-layer heat shields. The rear delta ring assembly is the same part used on rifles, but the front cap is round rather than triangular. Military caps may be cut away to provide clearance for the M203 grenade launcher.
Like the rifle caps, the center hole diameter increased from .625″ to .750″ to fit the heavier M4 barrels introduced in the 1990s. M4-style handguards are actually oval rather than round and contain double layer heat shields.
A commercial variant of the carbine with a slightly longer gas tube known as “mid-length” and sporting 9-inch handguards has become common in the last six or eight years. The handguards are round like the original carbines and are retained by the same delta ring and round handguard cap.
To sum up, the delta ring is universal for all variants. Handguards will be 7-inch round for carbines, 9-inch round for mid-length carbines or 12-inch round or triangular for rifles. Handguard caps are round for carbines in standard or mid-length and triangular for all rifle variants. Please refer to the accompanying photos to i.d. parts.
- <h2>Slip ring</h2>Slip ring types include the old straight-sided model of the M16A1 (l.) and the current tapered delta ring. Functionally, they are interchangeable.