A customer returned to your shop and informs me that his customized Remington M700’s shot groups have considerably increased over his last few range sessions. While inspecting the bore, I notice severe pitting from the chamber through to approximately 10” down the barrel. The customer informs me that he has recently started shooting corrosive surplus ammunition. After presenting the customer with his options (rebarelling vs. lapping) the customer has requested I lap his barrel.
Create a discussion addressing the following elements:
- The materials & tools required
- Construction of the lapping rod
- The process used to lap the barrel
The materials & tools required when lapping a barrel include calipers to take measurements, a hand torch, steel cleaning rod with a rotating handle, liquified lead and a means to pour it accurately, some oil and finally some lapping compound. Construction of the lapping rod may begin by wrapping a piece of cotton or twine around a section of steel cleaning rod and pushing this rod down the barrel until a few inches from the muzzle thus creating some kind of plug. Taking a low temp torch, heat up the barrel in a way that would melt solder but not damage the finish on the barrel. Now, using some melted lead and a ladle of sorts, pour a small amount into the barrel. This should imprint the rifles lands and grooves and melt the lead directly onto my steel cleaning rod.
So with this new cleaning rod I have created, I will let it cool slightly but then I will push it about halfway out of the muzzle. Please be sure not to remove this entirely because you will need to start over again. If you find any burrs or damage to your rifling imprint, take a few files and be sure to take your time working them out. Now move the barrel in the vice to a position you can work the new lapping rod in and out of. Apply lapping compound to the rifled part of this lapping rod and add oil to the inside of the barrel. Begin to pull the lapping rod through until you reach the bore making sure not to completely remove the rod. Continue this back and forth adding more lapping compound as needed until the barrels rifling improves.
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