Welding on a new bolt handle is a standard job when customizing a military action rifle.
To properly set up the bolt for welding, you'll need a bolt welding fixture to hold it in perfect alignment. Secure the handle first and then the bolt. Once the screws are snug, you can adjust the position of the handle so that it's properly lined with the bolt.
A heat sink and heat control paste will help pull the heat away from the critical areas of the bolt.
We use a TIG welding system to attach the bolt, but oxy-acetylene or electric arc welding works fine as well.
And that's how you weld on a bolt handle. Now it's ready for lifting, sweeping, and polishing.
-- Larry Potterfield