.308 Throat Erosion

[curisu]

I've searched this site and google in general for baseline information regarding throat erosion. The general consensus is that .308 is a pretty soft-shooting round, especially with loads well below SAAMI maximum pressures (<61k psi).

I've run ~2000 rounds of mixed SMKs & VLDs through a brand new Bartlein. I don't believe I abused it, but the barrel and chamber area were too hot to touch a few times. I probably averaged 1 round a min in practice, maybe a bit faster during classes.

All that, and after 2k rounds, i've measured throat erosion at around 0.04" - seems a bit extreme, doesn't it?

[highpower790]

Normal erosion from a stainless barrel!

[ar15barrels]

All that, and after 2k rounds, i've measured throat erosion at around 0.04" - seems a bit extreme, doesn't it?

Nope.
Seems a little low actually.

Good job on not overheating it so much.
I have a customer who shot out a Bartlein in 308 in about 900 rounds.
He got it smoking hot though...

[hermosabeach]

How have your groups changed? Or have the groups opened up at all?

[curisu]

@randall, thanks, i just thought of .308 barrels are relatively long-lived (5k+ accurate shots). and i was hoping to run a good accurate load + COAL for more than 200 rounds at a time.

@hermosabeach - the groups at <500 round count had a fair number of 1/4-3/8" 5-shot groups, probably with an average of 1/2-3/4" with all my amateurish "pulls". at 2k, it feels like a 1/2" group is a good set, with most 3/4-1".

marc soulie trued and barreled this setup (while i wait on my 6.5 build from him), so I was hoping to stretch the barrel life til October . I'm going to do a deep cleaning with copper removal this week and see if i can get my groups to tighten back up to sub 1/2". else, marc says that he'd be willing to borescope it and tell me if i'm looking at a new barrel or not.

[killshot44]

Patches wet with Kroil and with some JB paste should clean anything out. Just go easy.

Could alway have Marc do a set-back rechamber and refinish the crown if it's gone sideways and you don't want to spend for a new barrel.

[JMP]

I am having trouble killing my current 308, Bartlein 1:12". It's ~5k. But, I just run 168s and don't really try to hit much past 600, 800 max. I've had the replacement blank quite a while after waiting a year for it. It's them 1,000+ yard 308 shooters, I think, that rock their barrels.

[thospb]

The USMC expects to get 12,000 rounds from a barrel before accuracy degrades. My last .308 barrel I went over 10,000 rounds. Just clean it when the groups begin to open up. I have only cleaned my barrel once in 200 rounds.

[curisu]

maybe this had something to do with it...

[JMP]

I have a customer who shot out a Bartlein in 308 in about 900 rounds.

What was his load? For that, why not just shoot 300 WSM or 300 WM. Seems like you are kind of defeating the purpose when you could be running a better cartridge in the same barrel.

[thegiff]

From 2 different usmc sniper instructors the Pendleton snipers usually pull barrels at 8000 rounds and 1 moa. They don't chase the lands though.

[jimmykan]

... i was hoping to run a good accurate load + COAL for more than 200 rounds at a time. ...

So you are averaging .002 of throat erosion every 100 rounds.

If you need to adjust CBTO every 200 rounds, that means the Berger VLDs will only tolerate a .004 range of seating depth?

That's harsh man... No wonder the hybrid ogive bullets are so popular now!

[ar15barrels]

@randall, thanks, i just thought of .308 barrels are relatively long-lived (5k+ accurate shots). and i was hoping to run a good accurate load + COAL for more than 200 rounds at a time.

When "match grade" accuracy is required, it's common to rebarrel 308's around 3000-4000 rounds.

[ar15barrels]

What was his load? For that, why not just shoot 300 WSM or 300 WM. Seems like you are kind of defeating the purpose when you could be running a better cartridge in the same barrel.

50+ gr of RL15 if I recall.
He was running 3050fps with 155gr bullets from a 20" barrel...

[JMP]

50+ gr of RL15 if I recall.
He was running 3050fps with 155gr bullets from a 20" barrel...

Wouldn't have been an issue if he just got a real barrel. Let that be a lesson to folks getting short "tactical" barrels. Start with 30", then you can setback if you need to, but you'll get fine velocity with the longer barrel.