Throat Erosion

[paid4c4]

I have an M1 Garand 5.8 M with the original barrel which has a MW of 2 but a TE of 7.5.
What causes TE and how can a barrel be good at one end and not the other?
Bill

[timshufflin]

I have an M1 Garand 5.8 M with the original barrel which has a MW of 2 but a TE of 7.5.
What causes TE and how can a barrel be good at one end and not the other?
Bill

I really don't know the answer, I can only kibitz from what others have said and give my own theories. I would guess that a barrel with a high TE has been fired fast and furious. I have noticed that the full auto's I've worked on had high TE's. The ignition that occurs between the setback of the throat and the round entering the throat causes erosion right at the entrance to the lands, the "jump" or "free bore" area. When shooting fast and furious, the metal in that area is softer and more apt to "erode" from ignition.

Okay, so the entrance to your rifling is a bit worn out, what to do? Get a throater and hog out your throat a bit. Your free bore will be longer so you'll simply load your rounds with a little bit longer Over All Length. This will essentially get you a lower TE with a new, longer, OAL cartridge. The TE we measure is compared to a SAMMI spec round.

[Dave Waits]

I have an M1 Garand 5.8 M with the original barrel which has a MW of 2 but a TE of 7.5.
What causes TE and how can a barrel be good at one end and not the other?
Bill

Bill, shooting the rifle causes TE! Just joking around. Throat erosion, like muzzle erosion(Not wear, no such thing) is caused by very high temperature gas scouring. The reason is simple on the second question, alot of slowfire and not much rapidfire(Which heats up the muzzle and softens it).

[Dave]

Hi throat readings do not necessarily mean you'll also have a high MW reading. I've seen club (authentic) match rifles that have been shot for many many years yet have been well cared for and cleaned properly and will show a TE of 8+ yet still have muzzles barely over 1 with bright shiney bores. One of my shooters from days gone by had an LMR barrel with a TE of 8 and a MW just under 2. Bright bore and strong rifling, it was an excellent barrel with the right loads despite the high TE reading. Not a 600 yd match rifle but was great for the majority of 100 yd plinking I do as that is all we have at many of the local ranges around me.