speed squats will train your muscles to 'turn on' faster / more explosively.. BUT.. unless you have the muscles to begin with, no amount of speed training is going to get you dunking.
squat more weight the conventional way to add muscles. it is easier to be explosive once you get stronger.
6 total reps of 265 at your weight, even if repped as fast as possible is not going to do anything. do something like 40 total reps of 80-85% RM 2x/week.. and eat a cow.
forgot to add.. a projected 420x1 squat single is not going to get you jumping high. 345x6-8reps will help vert more.
Thanks Kingfish for ur feedback. I think my 1rm raw squat is around 380lbs, but I am Grinding up with such weight and lack of explosive power.
After setting the local city squat record I am done with slow powerlifting squat style. I want to tranform all my muscle in the explosive power. Personaly, i feel like a Slow 18wheelers, power is there, but unable to release it in a quick explosive manner.
So, I am sure 346lbs x6-8 reps is good for power... But i am not sure how that can get me higher...
I just strated doing speed squating... so may be the weight is not as heavy as I should. But i can feel my knee is having some problem since I shifted from powerlfiting to Vert training...
110517 Vert Training
Upperbody routine x 2 with 60-70% weight in a explosive manner
Hang Clean with Depth jump alternation
100lbs 3x3 (light but for god sake get it right and use ur Glute, upperbody should be relaxed)
110lbs 2x4
Depth jump with 1 step above knee height
Squat
87lbs 1x3
137lbs 1x3
157lbs 1x3
177lbs 1x3
197lbs 1x3
227lbs 1x3
247lbs 3x3 Slowing down but still pushing fast with no grinding
Reversehyper (suggested from Adarq, Keep the leg stright all the way to the top)
30lbs 3x8
Calfraise
30lbs 3x20 (doing it as explosive as possible all 20 reps)
I am doing 3-4 Max run up jump in my weekly basketball meeting every sunday. I don think it is enough to consider as Max effort jump training. However, i can confirm that i am NOT getting any higher still.