Barrel extension wear FYI

**308sako** · 03-10-14, 19:47

Pebble4300rounds004_zpsb85f0d7f.jpg

Melonited barrel with 4358 logged rounds. The barrel extension turned off before the AAC 51T Miter mount so I got to see something unexpected. The bolt, a Colt has nearly 12,000 rounds and looks new by comparison. Apparently the relative hardness of the extension may have suffered in the heat treatment of the melonite bath.

**Eric D.** · 03-10-14, 19:53

I remember Grant mentioning that barrel extensions are prone to loosening after a barrel assembly is melonited.

**Col_Crocs** · 03-10-14, 20:13

^^ Yes. Constructor mentioned meloniting barrels with the extension off for that very reason. I dont know about the wear though... AFAIK, the process should increase the surface hardness of the extension. One issue I have read, IIRC, is the possibility or instances of the extension becoming brittle. I dont know if this had to do with the length of time the process took to do a barrel correctly and thus affecting the relatively smaller barrel extension or the process itself, regardless of duration, due to the minimal surface area of the extension.

**markm** · 03-10-14, 21:07

Great pic of how an extension wears and headspace can become problematic. Not sure about the fruit finish nonsense piece of the equation.... but this pic illustrates why the proper heat treat/hardness on an extension is critical for longevity.

**308sako** · 03-10-14, 21:54

I wish the picture I took of the bore was as clear, the 4358 rounds haven't begun to wear the bore.

Yes, I think this is a rarely seen item of interest.

**Eric D.** · 03-10-14, 22:30

I had to go back and look at that

I don't know how I missed it before.

Originally Posted by markm

Great pic of how an extension wears and headspace can become problematic. Not sure about the fruit finish nonsense piece of the equation.... but this pic illustrates why the proper heat treat/hardness on an extension is critical for longevity.