Garand barrel crowning/erossion question?

[glockster157]

I am just getting into Garands and one of the things I have learned is that after a number of rounds you not only get throat erosion, you will also get muzzle erosion. My question is how far back into the barrel does the muzzle erosion go and can barrel life be extended by recessing the muzzle with a inset crown? How deep can you reasonably push the crown back. My family is loaded with expert machinists so getting this done is not a problem.

 

[Onmilo]

Muzzle erosion comes from cleaning rods, especially jointed cleaning rods, rubbing against the muzzle as the weapon is cleaned.
Muzzles and muzzle crowns get beat up from impact against hard surfaces like any firearm.

Recessing the muzzle has been used by a number of countries who have issued M1s.
I saw this modification done to rifles issued in a Central American country while is service.
The few rifles I have examined with this modification had the recessing no more than 3/4" back into the bore and well forward of the gas port.
A 5/16" end mill or 27/64" ball mill can be used to make the cut and a brass rod turned to the mill dimensions with the end rounded and treated with polishing grit can be used to smooth out the cut area.
One of the rifles I examined also had a crown reapplied to the cut area of the muzzle. HTH

 

[glockster157]

It is true that many a barrel crown is damaged or worn prematurely by improper cleaning and that military rifle muzzles take a beating but I am speaking of erosion. It is my understanding that even match guns that are cleaned by experts start to erode at the muzzle at a rate of around .001 or 1 mark on a muzzle gauge for each 1000 rounds fired. This is caused by the hot gases escaping around the bullet as it exits the muzzle. My question is how far back does this erosion extend as the wear increases. For example, if a muzzle gauges 5, is the erosion go back a 1/16", 1/32", 1/4"? and as the wear increases does it extend back farther or does it wear the same area deeper?