Listen to this! If you chop a barrel on a 30-06, you are likely going to be wasting a lot of unburned powder out the end of the muzzle. You just built yourself an excessively loud flame thrower. Short barrels = .308. End of story. Much more complete and efficient powder burn.If you cut that barrel on the ‘06, start researching a load that has a fast powder.
Traditional ‘06 loads out of 22” barrels are loaded with slow burning powders. Creating a lot of waste in energy in even a 22” barrel. Be ready for a severe muzzle flash in a 20” barreled version. You can mitigate that with a faster powder. However, you’ll never eliminate due to the heavier bullets the cartridge shines at.
If I were going to a more streamlined lighter package, I’d just buy a 18” barreled 308. For the ranges you are going to shoot, it’ll do great. I’m speaking from the experience of doing just this recently. And, after doing so I’d never shorten the barrel on an ‘06 if buying a compact 308 was an option.
A lot of people say the calibers are basically the same. They aren’t. The ‘06 is so much more capable. And, you don’t see that until you get the 24” barrels. But, you don’t need that. So, keep the gun you have and buy the compact 308. You’ll be glad you did.