It's a bit more drawn out and complicated than that. Colt Canada supplies several NATO countries.
The C8 SFW started out as a prototype for UK SF and became known as the SFW after four more NATO country's SF adopted it. There were two sleeves: one for simon grenades and one for a particular brand of suppressor. The original SFW also used a heavy solid forged gas block/front sight forging.
Many of these were sold with KAC RAS.
The C8 was a pencil barrel with C7 style carry handle upper. It was made on a standard mandrel for the hammer forge.
The SFW used a proprietary improved chamber design that required a new carbine mandrel, a longer barrel for improved velocity and a heavy barrel for increased rigidity and more thermal mass. All carbines use this chamber now. The barrels were tested at different lengths for maximum accuracy nodes, hence the 15.7 length.
The C8A2 was a heavy barrel 14.5 in carbine with a weaver upper for the Dutch and was often called the Dutch barrel. The majority of early police sales used C8A2 with 1913 uppers.
Canada adopted a flat top before the US adopted 1913. The weaver was more accurate and consistent. The new NATO rail standard uses some weaver features.
The CF adopted the new improved chamber for C8's but did not designate a new weapon. There was a small 2 roll marked on the barrel to indicate improved carbine chamber - but they kept the pencil barrel.
The C8A1 was a pencil barrel with a flat top upper.
The CF then adopted a small QTY of C8FTHB for urgent operational requirements which was essentially an SFW - but with weaver upper, and a M203A1 sleeve. There were also a few upper kits. These were ones that may have been painted.
The sleeve is required to be milled from pre-hardened steel to be able to handle the loads required. This makes it quite expensive and hard to machine - particularly in small QTY.
Later, after the C7A2 mid-life program was running, to consolidate the fleet, the CF adopted the C8A3 - essentially a C8FTHB with ambi controls to match the C7A2, Canadian average green furniture, etc.
The reason that these were so successful is that Diemaco was a full MILSPEC facility, NATO AQAP certified, contained a full test and evaluation centre and was willing to do R&D and produce short run, specialized products and test and certify them to the NATO standard. Canadian MILSPECS often exceed US or NATO specs - for example Cold testing. US MILSPEC is for 36 below, Colt Canada tests to 65 below. To make a rifle suitable for arctic ops, the chrome was upgraded to a thicker, more ductile hard chrome that performs well in extreme high and extreme low temperatures.
These barrels outperformed all competitors in the UK trials and in fact were the only rifles that did not need to be re-barrelled. Some trial guns were used operationally after the tests were concluded. To put it in perspective, the testing cost more that the contract was worth.
As a comparison Colt's produces about 650 rifles a day which would be a month's production for Colt Canada. The barrel steel for the Colt Canada cold rotary hammer forged barrels is the best in the world. The steel un-drilled blank costs more that a completed chromed M4 barrel. Each barrel, bolt and extension are MPI and marked with a batch number for tracking as extensive destructive testing is done on every batch. Every barrel is air gauged twice, scoped twice and every one is test fired.
