A lot of it depends on exactly how much resolution that you want and how much you want to pay. Very basic borescopes that require attachment via usb cables to computers have 640 x 320 res or 1280 x 720 resolution are available at some pretty cheap prices on Amazon.
However, to use on in a 30 caliber barrel, you need the camera size to be 6.5 mm or below. The smaller the camera head, usually the lower the resolution offered or it is higher priced. I use a cheapie $40 one to check out old milsurp barrels for things such as washed out rifling etc, patches of dark spots etc. The resolution is adequate for finding relatively large problems in a barrel but not for example to determine throat condition as an example. I bought it originally to determine conditions behind drywall and to check the condition of a lawnmover's piston surface through the spark plug hole.
The Hawkeye is the best right now specifically for rifles etc. but just like Oehler's chrony, the king will be increasingly challenged by the better faster cheaper revolution in electronics. Lyman's new borescope the first shot over the bow at SRP 299.99 and I expect there will be others following.