OK
For your 38SPL, you probably don't need to actually slug your barrel bore (since it's S&W, it's got an odd number of lands which makes measuring groove diameter a bit complicated for shade tree machinists, just like mine!). That dimension is pretty much "standard" for modern firearms. Doesn't vary enough to make measurement worthwhile.
BUT, for a revolver, you should slug each cylinder's throat diameter. That's the critical dimension for bullet sizing for this type gun.
If you have pin gages (they are about $2-3 each from McMaster-Carr, which is a FANTASTIC company to support btw), they're easiest. Find the largest size you can get (+/- 0.0005") which will drop through a given chamber. Number your chambers! If you don't have pin gages, a lead slug (e.g. oversize bullet or fishing sinker) can be driven through the throat and simply mic'd. DO NOT USE CALIPERS! Hopefully, all your chambers will measure the same enough. Otherwise, life gets complicated again and the price to play continues to increase.
For your 9mm (i see it's semiauto), or if you want to measure your revolver's bore "properly", just so you know, you just drive the slug into the barrel with a thick (e.g. 8mm) dowel and a hammer. About .360"+ diameter. "Size 9" quarter oz lead egg sinkers work for me (in 38SPL). Once it's started into the barrel, pushing it out is really not too hard because it will just track the rifling.