Your Coil Temperature could very well be going over 450F. You might be Exceeding 450F on the 1st Hit. Chain vaping or Not.
And if it Isn't going over 450F on the 1st Hit, a lot Depends on the Amount of Time between 2 sequential hits if you are going to reach a given Temperature or Not.
Here is something I posted in another thread where Coil Temperatures have be Extensively Discussed.
Just an Update.
OK... I did a Fresh build on my Subtank Mini. It was 316L 26ga 3mm Coil @ 0.35 Ohms. Put it on a eLeaf Pico with TC set at 420F and 16.0 Watts. e-Liquid is 20%PG | 80% VG Unflavored. Muji Cotton Pancake wicking was flavored with Watermelon/Strawberry DIY. Airflow is set to 35% Open using a Toptank Mini New Style Base.
With my normal 5 ~ 6 Second Hit, on 30 Second Intervals (6 Hits Total), the TC never came on.
Doing a 5 ~ 6 Second Hit, on 5 Second Intervals (6 Hits Total), I did get the TC to come on after the 3rd Hit. And TC did Kick in Very Quickly on the 4th and 5th Hit. On the 6th Hit, TC was on about at the start. And the Normal Flavor had diminished. Not Burnt Tasting. Just Over-Used and in need of Rest tasting.
Also, I was able to get the TC to come on if I did Long Back-2-Back Hits with No Rest Interval between Hits.
Also have a Mild Nic Headache. And am in Need of a Big Glass of Water.
Be it Far from a Conclusive Temperature Test, I could see that as I shortened the Time Period between Hits, that the Coil Temperature would Exceed the 420F I had the TC set to.
By the Same Token, I also saw that I could Vape Constantly and Not Exceed the 420F TC Limit as long as the time between hits was 30 Seconds or More.