Range day cut short

I took my Mac N Cheese out for a test ride and 15 rounds in the rear started to rise and eventually broke the rear piece and the picatinny insert.

Filament used was Siraya tech PAHT-CF , filament was dried prior to usage and kept dry during printing .cooling turned off, 10 + walls ,top/bottoms , were applied , printed hot and slow on my Bambu P1S .

Fit and function were perfect before firing curious as to where I went wrong , I’ve printed a new rear piece and insert with 20+ walls and 15 top/bottoms .