No gun, rev or semi is 100% reliable 100% of the time. Just about a month ago, the firing pin on my friends M29 broke off.
Carry multiple guns like flopshank, and others, and if one gun malfunctions or breaks, go to the next.

In answer to your belt question, many good gunbelts have a curve to them that conforms to your body. Virtually all are two or more pieces of leather stitched together, and many have a kydex or other stiffening material between the leather inner and outer layers. Lots of belt makers mentioned in this section of the forum.

No problem with a 4 incher. Mr. Ross carries his 4" 500 Mag in a holster in his waist band sometimes. He carried it for quite a while when teaching his CCW classes I read. His students were surprised when he pulled it out because you couldn't tell by looking that he had something that big on his body.

I carry my 4" 500 Mag in a shoulder holster when I wonder into the woods sometimes or when it's cold weather under a coat which is rare here in this furnace in the South. When it's hot I'll sometimes carry it in a fanny pack. I put smaller K frame grips on it when I carry it.

Smitty

Generally my carry guns are either a PPK in 380 or a XD9SC with both a XD45C Service and XD45C Tactical available if I feel like carrying some heavy firepower. To that list I will be adding a 625 Mountain Gun and 25 Mountain Gun, both in 45 Colt, as soon as I get some work done on them and get holsters. Btw, Cherryriver thanks for the comments about the Simply Rugged holsters because I've been looking for something other than the IWB holsters I have know, I hate the things.

I once had a neighbor who was Special Forces. His choice in handguns was four inch nine-shot High Standard .22LR. He said in nine shots, you will likely hit your opponent at least once enough to bring him down. You can then kill him easily after he's down. This seems to be an approach widely adopted by gang bangers today. Spray and pray that one goes down. Then finish him execution style. I recall a killing in this manner near Huntsville, TX in the eighty's. A UPS delivery man refused to hand over some COD tennis shoes to some country brothers didn't have the money. Long story short, he had to take off running through a pasture. The perps brought him down with a shot to a foot, then walked up and shot him in the head. I reckon that's the new country living. Wonder of Obama thinks those black flatland country folks cling to their antipathies, their guns and their religion the same way those white crackers do in Virginia and the surrounding hill states?