In a method of synthesizing a silicoaluminophosphate molecular sieve having 90+% CHA framework-type character, a reaction mixture is prepared comprising sources of water, silicon, aluminum, and phosphorus, as well as an organic template. In one aspect, the reaction mixture is heated at more than 10° C./hour to a crystallization temperature and is retained at the crystallization temperature or within the crystallization temperature range for a crystallization time from 16 hours to 350 hours to produce the silicoaluminophosphate molecular sieve. In another aspect, the reaction mixture is heated at less than 10° C./hour to a crystallization temperature from about 150° C. to about 225° C. and is then retained there for less than 10 hours to produce the silicoaluminophosphate molecular sieve. The molecular sieve can then be recovered from the reaction mixture and, preferably, used in a hydrocarbon conversion process, such as oxygenates to olefins.