I need to enlarge the 44 cal. loops on a western style gun belt to work with 45 ammo. Any help appreciated.

I'd say just get your 45's in there and leave them for a few days.

I don't see why you couldn't moisten (for example, with a sponge or rag) the loops, jam your cartridges in while still wet, and leave until dry.

As mentioned above, dampen the loops and stick the 45 ammo in them. Let dry, then oil the loops
Bear in mind, there is usually no going back.

I read online a suggestion to use a light misting of alcohol and water. Don't saturate, just dampen. Insert the preferred pistol or in your case, cartridge and allow to dry.

I've done this process with 1.5" leather holster loops to stretch to 1.75".

Alcohol will help leather stretch. Regular old rubbing alcohol. Get the high test.

Treat the leather after.

Dummy cartridges and moisten the leather.