In this work, an effective, but still not well-explored area of red flare pyrotechnic formulations was investigated. High magnesium content (40-60 % w.t.) and the presence of conventional gas generating materials were the specific features of formulations explored herein. Such illuminant compositions possessed a low burning rate and high specific luminous intensity. The investigated system was based on strontium nitrate, rounded magnesium powder, chlorinated rubber, binder and gas generating additives. Emission spectra, light intensity and burning time have been measured during the experiment and recalculated to the specific luminous intensity and color purity. Additives in the form of 2-cyanoguanidine, Melamine, Azodicarbonamide, Calcium resinate, Shellac, Strontium oxalate, Lactose, Dextrin, Phenolic resin, Lignin sulfonate, 5-aminotetrazole, Urea, Guanidinium nitrate (GN), Hexamine and Sulfur were evaluated in Mg-rich flare compositions. The use of GN was studied more carefully as an exceptionally efficient additive that increased the flares light intensity by 60 %, in comparison to the standard GN-free composition, while maintaining high color purity of 90-97 %.