I have been researching the 450 pistol with focus on the Windham Weaponry 450 Thumper pistol with a 9" barrel. Of course like most firearms there are none immediately available but some retailers and Windham do accept backorders. After several days of investigating I thought it was time to open a question here and request whatever info those with 450 experience/knowledge could share with this A/R novice. My experience thus far consists of a new Daniel Defense DDM4 V7 in 300 Blackout and I am thinking about purchasing the Windham 450 Pistol upper. One of the shortcomings is the magazine limitation of 5-7 rounds.