Heat it up?

I had a leak in the lower sight tube barrell bolt and want to reuse the brass washer.
Can I heat said washer to get it to expand for reuse?
How hot and will I see the expansion as I can see the crush mark in it.

If it's copper and not brass you can anneal it. Heat it till it turns red and quench in water, it will be dead soft at that point and ready for re-use. Metals don't expand with heat, just turn liquid when hot enough.

thanx, will do