Copper magnet wire is used to wind CCL coils. The range of wire gauges is perhaps 32 to 40. 40 American wire gauge (AWG) is very fine and delicate stuff, about the diameter of a human hair. Many shooting CCL coils are wound with 34 AWG wire, while many logging CCL coils are wound with 37 or 38 AWG wire. In actuality, the gauge is not particularly critical in most applications, with wide variations in wire gauge producing acceptable results.
It is important to maintain proper tension on the wire during winding or coil failure may later result, especially in the case of shooting CCLs where the coil is subjected to significant stress during shooting operations. Table A below gives recommended winding tensions and some other useful data for round copper magnet wire in the size range of 26-50 AWG. A few manufacturers potted their coils in epoxy, or used "wet winding" where a bonding agent fuses the windings together in an effort to ruggedize their coils; both are nightmares when rewinding is necessary.
AnaLog Services, Inc. rewinds all types of CCL coils using only the best quality magnet wire with proper tensioning to insure long coil life. We also offer a proprietary resin impregnated coil for the most demanding shooting CCL applications, but this extraordinary measure is seldom necessary. Visit our Coil Winders, Dereelers, and Tensioners page for a look at some of the equipment we use to wind CCL coils.
The original magnet wire was insulated with enamel or varnish, but modern polymers are vastly superior. Magnet wire insulation is designed to be as thin as possible (thus taking up minimum space in a coil) while still providing adequate protection. The various polymers used are rated by "thermal class", typically 105, 130, 155, 180, 200, and 220 degrees centigrade. The insulation is also specified by thickness, single build, double (heavy) build, triple build, and quadruple build. Double build, 200 degree insulation is a good choice for most CCL coils.
Table B below provides information about commercially available magnet wire most likely to be used in winding CCL coils. Table B is especially useful when purchasing magnet wire in the surplus marketplace, since said wire is often identified only with manufacturer abbreviation codes. Table C below gives DuPont's recommended allowable NEMA standard magnet wire substitutions.
See MWS and WireTronic (free software) for more information on magnet wire.