This drop-in upper will attach to virtually any standard AR-15 lower assembly. Comes complete with charging handle, bolt and bolt carrier assembly, it is ready to pin to a complete lower assembly without modification. The AP4 upper is an A3 Flattop with a light contour barrel. This upper features GlacierGuard handguards which are an AP4 style handguard that utilize 15 internal fins, rather than the standard aluminum double-shield, for heat dispersion. These unique fins, while dispersing the heat generated by rifle fire, also provide unsurpassed strength and rigidity for the handguard. Externally, the AP4 "GlacierGuards" feature 15 ribs that mirror the internal fins, and provide the shooter an enhanced grip.
NOTE: DPMS 6.8mm SPC barrels are threaded 1/2"x28, the standard thread pitch for 223 Remington caliber muzzle brakes and flash hiders. Using a 223 Remington caliber muzzle device on a 6.8mm SPC barrel could be dangerous and should NOT be attempted. If an aftermarket muzzle device is to be used with this upper receiver, please be careful to select one of the proper caliber.
AR-15 Hammer and Trigger Pin Dimensions:
Some Colt® AR type rifles have been manufactured with hammer and trigger pins and holes which are approximately
.176" in diameter. These are referred to as "large pin" Colts. This was done to eliminate the chances of someone putting M16
fire control parts into an AR receiver. This is not found in all Colt models, just some.
All other AR type rifle manufacturers have stayed with the .156" diameter hammer and trigger pins and holes, or "small pin"
which is the same spec used in all military M16 rifles.
Measure your pins or the holes in your lower receiver to determine if you have a "small" or "large" hole Colt® AR
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