Hello guys, I have a M&P-15 lower, and a M&P 15/22 complete rifle, I was curious if the lowers had any significant difference, I have a Alexander Arms .50 Beowulf upper on my M&P-15 lower, I am looking to buy another .50 upper, But would prefer not to buy another lower, Is anyone familiar with the two? If so what are the differences, I ask because I am told they are the same, But I am new to the tactical rifles genre and just don't see how they could be the same.
Thank you for the help.