One of the biggest misconceptions in the weightlifting world is that a lifter must have big deltoids and deltoid strength in order to gain bar stability overhead. To bust that myth one must look at the two pictures above. The deltoids serve to hold the bar in place IF the bar is out front and away from the stability of the hips. What’s more is that the deltoids aren’t designed for stability. They are designed for power application. The traps are designed for stability. The traps are a HUGELY bigger muscle and allow for the lifter to keep the bar over their center of gravity. A lifter who has their traps engaged and has the bar stable over their hips (second picture) will achieve better external rotation of the shoulder and thus a more stable overhead position.
Completing a jerk while using the delts as a stabilizing muscle will only internally rotate the shoulder, push the bar away from the lifter, and create more misses than makes. Getting the head through the bar and getting the weight of the lift over the much more stable traps creates good external rotation and overall stability.
Jon North once said in a radio broadcast that when completing a jerk to push your head through the bar like a turtle’s head out of its shell. This creates a a position where the bar is over the traps and stable. This is a strong position. Leaving the deltoids to stabilize the bar will only lead to failure and instability.
Get your head through the bar and use those traps!