What is the safest way (to the gun) to slug the bore of a ML rifle with out takeing off the breach plug?

Hi, doesn't look like anyone got to this, so I'll see if I can help.

You can get a fairly close measurement with a dial caliper. Make sure the gun is unloaded and clean (of course). If there is an even number of lands and grooves, you should be able to take a measurement at the muzzle of the lands and grooves. Take a few readings at different angles on the bore to compare.

To slug it, take a soft conical slug that is atleast as big as the measurement you got with the dial caliper. Set the butt on the ground and position the slug on the muzzle. Use a small hammer to lightly tap the slug in about 1/4-3/8". Use a vise grip to grab the slug and pull it out. Use your dial calipers to measure in a couple spots and compare to the original readings.
Wiggle it lightly if it won't come easily. If you twist it back and forth, it will mess up the measurement. You can try a couple slugs to compare measurements.

Remember, soft slug, small hammer, go lightly.

This will give you a good idea of your bore, but will not show any tight or loose spots in the rest of the barrel.

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