M16 barrel erosion study

AR/M4 AR Technical Discussion
1

The following abstract was taken from DTIC, and is an old 1966 study:

Twelve rifles, 5.56mm, XM16E1 were fired to the end of their barrel bore service life. Measurements of the barrel bore were taken periodically with an air gage, and an expanding mandrel gage. It was determined that the maximum acceptable barrel bore diameter would be 0.2206 in. The barrel bore was considered serviceable for either overseas or CONUS use if that diameter had not advanced forward of the origin of the rifling further than 3.625 inches. Advancement to 6.625 in. was considered the cut-off for CONUS use only, and advancement beyond 6.625 would constitute complete rejection of the barrel. Gage, Barrel Erosion C7799792, designed by Springfield Armory, is recommended for this purpose.

Is this still a valid assessment or are different standards applicable nowadays?

2

We would check the barrels for pits and cracks.
Check head space.
Check with a straightness gauge.
Check with an erosion gauge.

If I remember correctly the erosion was a simple go/no-go

3

FWIW: DTIC has some later studies dealing with measuring barrel erosion in M16A1 with chromed bores. If I remember correctly, they had to switch to different No Go criteria from those used with XM16E1 with non-chromed bores.