Colt Canada C7 - Wikipedia

Diemaco changed the trapdoor in the buttstock to allow easier access to a small storage compartment inside the stock, and a 13 mm (0.5 in) spacer is available to adjust stock length and length of pull to user preference. For the furniture Diemaco chose Fiberlite nylon-reinforced polymer suitable for CRBN decontamination and cold weather use at −68 °C (−90 °F). The carrying handle and rear sight assembly on top of the Diemaco C7 receiver features the most noticeable external difference between American M16A2s and C7s. Diemaco C7s use a modified pre-M16A2 style two aperture L-type flip rear and front post iron sight line featuring two combat settings. An approximately 0.070 in (1.8 mm) diameter aperture rear sight is used for normal firing situations for target distances up to 400 m (440 yd). A second larger approximately 0.200 in (5.1 mm) diameter aperture battle sight is used as a ghost ring for short range quick target engagement and during limited visibility.[3][4]

The wing guards protected front sight was changed to a slimmer tapered round post of approximately 0.050 in (1.3 mm) diameter. C7 iron sights are normally zeroed with the normal use rear aperture sight at 300 m (330 yd) with SS109/M855/C77 ammunition. The rear sight can be zeroed for windage in 2.8 cm or 0.28 mrad increments at 100 m, when used with a 502 mm (19.8 in) rifle length sight radius. Elevation adjusting can be zeroed in 3.5 cm or 0.35 mrad increments at 100 m.[3][4] Not so apparent is Diemaco's use of 1 in 178 mm (7 in) rifling twist hammer-forged chrome-lined barrel and chamber units with a slightly reducing bore diameter over the length of the rifling to increase longevity and accuracy.[5][6]

These features were introduced as the Canadians originally wished to use a heavy barrel profile instead of the M16A2 profile. Diemaco developed a different mounting system from Colt for the Canadian M203 grenade launcher variant for the C7 rifle family and the bolt and bolt carrier were produced from stronger materials. Diemaco optimized the rifle for using 5.56×45mm NATO C77 cartridge L109 ball and the C78 cartridge longer L110 tracer projectiles by using a redesigned buffer assembly, thus making the M4-style extended feed ramps later introduced in the Colt M4 carbine unnecessary. The Canadian C7 was initially issued with Maple Leaf embossed Thermold polymer magazines STANAG compliant magazines. As the polymer failed in the Canadian weather and with age, the C7A1 was introduced with US sourced aluminum STANAG compliant magazines. The C7 has a cyclic rate of fire of around 700–900 rounds per minute (RPM).[7]