Then we're using and doing different stuff.
US military method in 30 caliber rifles with their throat erosion gauge let it go in 1/10th inch further about every thousand rounds. .001 inch every 10 shots.
We are indeed talking about different stuff. It sounds to me like what you reference is expected erosion and likely applied to all 7.62s to include M-60 and M-240 machine guns. Once the barrel gets hot, sustained fire can cause a lot of erosion. I guess that could also happen in an M-14.
I measure my throats all the time with my modified Hornady tools, and also look with a borescope, so I know how much throat erosion happens with all the different cartridges I shoot.
The worst I ever had was a SS Sendero in 7mm Rem Mag I bought new in 1996. It's throat moved .040" in 400 rounds which matches the rate you are describing. The 7mm RM is known to be hard on throats, and some suspected Rem got a bad batch of stainless steel then (mid 90s). For that rifle I would shoot five in a row and then let it mostly cool.
I traded that 7 Mag in on a 300 Winny Sendero in 1997. I babied that barrel, shooting only three shot groups and keeping it cool, and that throat moved about .010" in 800 rounds.
After that I paid a lot of attention to throat erosion, moved to aftermarket barrels, and eventually upgraded to CRF M-70s from Remmys for hunting guns.
When I started competition 1000 yd BR shooting in 2005, my first rifle was a 6.5-284 with a Krieger barrel. It's throat went .038" in 830 rounds. LR BR is hard on barrels, especially the Heavy Gun class where we get the barrels warm to hot during the sighter period then fire 10 rounds in 30-60 sec for record. Also, the 6.5-284 is known to be hard on throats, and I was shooting in Tucson back then. The next year I build a 300 WSM and in 658 rounds it moved the throat .007".
In my return to LR BR a couple years ago almost everyone had just moved from the 6mm Dasher to the 6 BRA. The Dasher usually tuned at 2950-2980 fps even though it could shoot 100fps+ faster. The 6 BRA also usually tunes 2950-2980 and has a grain or two less capacity. The reason everyone went to the 6 BRA was because of the risk of the throat eroding over a multi day match and putting you out of tune.
Throat erosion doesn't happen evenly all the time. It usually moves slowly at first, stays, then jumps a little in the Dasher. We think the BRA is slightly less susceptible to all that.
That is my experience with throat erosion, and it is all anecdotal. I would not dispute what someone found under specific and controlled circumstances. My uncle was an FE and top turret gunner on a B-17 in WW-II. He was supposed to shoot in short bursts to preserve barrel life and accuracy. What he did was strat shooting as soon as an enemy fighter began the attack and held the trigger down until the fighter turned off. He said many a fighter would turn away when he saw he was being shot at. My uncle said he wore out a set of barrels on every mission. I am
sure the the allowable throat erosion was exceeds for the 50 BMG. The rifling might have been awfully worn too......
