There is an argument that if you shoot 38 specials in a 357 magnum revolver, or 44 specials in a 44 Magnum or 45 Long Colt in a 454 Casull, that there will develop a carbon ring or some sort of condition where if you then put in the longer magnum length case- excessive pressures will occur. I understand the shorter case could leave depo0sits but if you clean out the chambers with a brass wire brush, etc. shouldn't that remove any fouling so that this issue doesn't exist, or.....is there something else occurring that I am not understanding? Thanks for any help.

I think it’s simply a matter of cleaning. I’ve shot many rounds of 45 Colt out of the 454. I don’t know about a pressure spike of relevance but it is harder to chamber the .454 after the 45 Colt.

I would think it builds start pressure and depending on the amount of the carbon ring can increase the start pressure quite a bit. A heavy crimp also increases start pressure and is recommended with heavy charges of powder like H110 for a couple reasons, keep the bullet from moving in other chambers of revolver and more efficient powder burn (powder burns more efficiently under higher pressure) .

The carbon ring limits the amount of case expansion releasing the bullet, the larger the ring the more it restricts it. Also when you shoot some say 38 spcl in the 357 chamber then 357s you compress the carbon ring that made it tight chambering the 357 making it a little more difficult to clean out being packed into the chamber walls.

It is a good idea to clean the chambers after shooting the shorter cartridges before switching to the longer charges, pressure can build, I do not now how much but it is easier to clean between switching rounds than to clean after packing it with pressures from the longer cartridge.

I inherited a single shot Ithaca 22 lever action from my grandpa. He used it on his 5 acre lot in town to shoot squirrels etc. with CB caps. When I got ahold of it i chambered 22 LR's and every one of them would stick after firing. Little scrubbing with some hoppes #9 and a brush and it was good as new. 22 is a little different animal though.

If I let the carbon build up in the Python, 357 ammo does chamber with more effort. Not an issue in the 686 though, and I assume the 686 chambers are a bit looser. Just a theory, so you 686 guys please don’t get on my case.

I load and shoot a lot of .38’s through a .357. Clean the cylinder every couple hundred and you’re good to go. That carbon ring can develop in most any firearm if your cleaning habits are neglectful. Different length cases in the same firearm make it more apparent.

Depends on the load and the powder. Also it's worse in a pistol caliber lever because it's harder to see and clean.

I don't shoot .38 Specials in ANY of my .357s. Most of the people that claim no issues do not load hot therefore do not see the erosion that can take place. It's more than a carbon ring in high volume guns.