And also make sure you aren’t damaging your firearm.   There are a lot of in between calibers that you might be able to get away with using a similar caliber, but it doesn’t always work.  Anyone that reloads ammunition is going to know the difference between a 9mm bullet, 38 Special, 357 Magnum and a 7.62×39 caliber.  You are talking about .311-.355 bullet diameters which all put them in 30 caliber ranges, but if you are trying to clean the bore and riflings, you aren’t going to clean them as well unless you use the correct brush. I’ve tried to cut corners in the past and noticed in some of my .357 revolvers that there was still lead build up in the chambers and the barrel if I didn’t use the correct gun cleaning supplies.

Gun lubrication is something you should seriously consider auditing in your inventory.   Much of the older stuff isn’t as good or it’s toxic and you should consider a total clean out.   Modern lubrication like Slip 2000 or M-Pro Series lube is far superior to the old gun oils.   Corrosion protection has also dramatically improved and that really makes a huge difference on blued guns especially many hunting rifles and shotguns.  Check all the Gun Cleaning Supplies like cleaning brushes you are using and consider making sure you are matching the calibers to the guns, if you are using too big of a brush you might end up scratching up the throat or chambers of a firearm.