The original barrel on my BM was a 5 1/2" slab side. Put a Challenge barrel on it a couple years ago. It looks good, shoots great and shaved a significant amount of weight. Nice upgrade on a 25 year old pistol.
I find the rubber Browning grips fit me better than the Challenge grips so they are staying the same. The original grips on the gun were the flat plastic type. The rubber ones came out a year or two after I purchased the gun and were the first upgrade.
.44 Special: For those who get it, no explanation is necessary. For those who don't, no explanation is possible.