I've used a standard old 2-AA flashlight with a Fiber Optic light-pipe to view inside the Bore of my rifles for many years. Also use a 1-AAA Mini-Mag to shine right into the muzzle.

Got a new 3-AAA LED Light the other day and the Light is so "White" and pure, I'm shocked at how well I can see in the muzzle with it.

But, it is so " BRIGHT " you absolutely DO NOT want to shine it in from the breech and look down the barrel at it.
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What kind of " Bore Light " do you all use?

I mostly use the standard AA fiber optic version. I've also got the same thing without the batteries and bulb which works pretty well as long as there's a halfway decent light source handy. But when worse comes to worse, the old white paper/business card in the breech trick works just fine.

I used the bent plastic one on a single AA for many years. Got the Nite-ize fiber-optic one for a mini maglite and it works well. Pretty bright though. They also sell lenses for these and if you install the blue lens, it is bright but not blinding.

A long wand flex light from Snap-On. Have used it for 15 years or more.

Use the 3 cell aaa streamlight with the flexible end piece, it is great--really bright like you said if you look down the muzzle at it.