In order to enhance muscle recruitment among the outer arms, take care to keep the tension on the side deltoids constant during the lateral raise. Use straps in order to avoid grip strength as a limiting factor and focus upon the side deltoids purely being responsible for the moving out action of the weights. If you wish you can use a bigger movement but would have it should be noted that going up to 90 degrees level i.e. till parallel to the grounds surface while taking the set to failure is also effective. Upon reaching the failure, also try a drop set where you reduce weight and reach failure again, this way you increase the volume without increasing the sets.