We don't know the weight of his gun. Even a mild load will back bullets out if the gun is light enough to move sharply during recoil. A heavy roll crimp can, indeed, make a difference. You can tell with a chronograph by the reduction in velocity variation.
That said, you can overdo a crimp and lift the sides of the case away from the sides of the bullet via the resulting bulge. The Redding Profile Crimp Die is the best solution I've found to that problem.
Jakopotamus,
Welcome to the forum. It looks like you haven't popped over to the General forum to introduce yourself in the
New Members - Please Introduce Yourself Here, thread.
If the bullets slid in with little friction, there's a chance yor sizing die is not narrowing the cases enough. I've run into that problem with Remington brass (R-P headstamp) in the 45 Auto. It takes a small base sizing die, like those made for the Dillon progressive presses, to get Remington's thin, springy 45 Auto necks small enough. Brass that is thicker and more readily resized would include Federal and Winchester and my personal favorite, Starline.