I have spent cases at my bench that I cut in half just for these situations. I remove the barrel, insert a case in the chamber, then use a can of flat black spray paint and give the case and barrel a little squit of paint. The area you are concerned with is at the bottom of the chamber. After you "paint" the area, remove the case and clean the paint off of the barrel before it drys. Now look at the paint line on the case and compare it to the cut-in-half case. This will show you where the case is unsupported by the chamber. By that I mean the case wall in front of the solid brass head. Once you cut a case down the middle, you'll see what I mean.
45 ACPs are a low pressure round because the chambers even in the old 1911s were not fully supported. A hot load or a bullet set too deep will increase chamber pressure to a point where the case could blow. Also, I've replaced several barrels where the owner got a little ambitious "throating" it.
Make sure your ammo is good too. If you're shooting reloads, pull a few bullets and weigh the powder to make sure you haven't over charged them. Check your COL and make sure the bullets aren't seated too deep.
