After working out for over 7 years, I have experimented with all types of chest routines to make gains on bench. From sets of 12-15 to heavy weight in sets of 3, I have struggled to find a routine that felt like it was working with optimal results. Then I remembered one of the original routines I did that greatly increased my bench in my earlier days of working out. That was the 5x5. I do not really know why I abandoned this format, because it worked miracles for me years ago. It probably had to do with over thinking my approach and believing I could improve on a tried and true method that was getting results. However it happened, I strayed away and now, years later, I have come full circle back to the 5x5.
The main thing that stimulates both growth and strength is being able to increase the weight and stimulate your body to adapt to a heavier workload (Along with proper nutrition). Doing five reps allows you to focus more on the amount of weight instead of just pushing for the extra reps. It simplifies your mindset and allows you to vary the amount of weight within a certain format.
By doing a total of twenty five reps, this is still enough to gain size along with strength. Dividing these reps into five sets will also allow you to have the option of not increasing the weight throughout all of the sets, but instead on only a few. This will make it possible to continually add intensity to your workout in small increments, which in the long run, will add up into substantial strength and size gains.
Keep in mind that this is a routine I use for flat bench and I alter the reps and weights for other chest exercises. Flat bench is often times the core to any chest workout and doing 5x5 will allow you to make gains on every aspect of your chest routine.