throat erosion?

[Rich Coyle]

How much throat erosion, in inches, does it take for a barrel to be worn out?

 

[Petey308]

In inches? This would depend on a lot of things, but ultimately it's "worn out" when it will no longer shoot your desired accuracy and changing things like seating depth, bullets, powder, etc doesn't help.

The amount of throat erosion when that happens will vary. Let your groups and target tell you when it's worn out, not your borescope. That's how I do it anyway

 

[Rich Coyle]

Petey308,

Thanks for taking a stab at it.
There must me some general knowledge with target shooters or cullers who use a barrel until it is no longer shooting "desired accuracy". Certainly, there is someone who has measured the throat when they no longer accept that barrel's accuracy. Are we talking 500 thousandths? Or is it more like an inch?

 

[dfanonymous]

There is no measurement.

As far as being able to tell, as said above, you'll notice a sudden drop off of accuracy. With something like a .308, there's quite a bit data on it, and you can expect this to be around 5000+ rounds.

With over bore cartridges it can be as low as 1500.

If you're a world class shooter and can manage 1/4 moa shots any day if the week, no excuses, what will happen is you'll start to get fliers. They'll be huge fliers, then your 1/4 moa gun is shooting like 5 moa. It works pretty much that quick. It's not a gradual thing per say. That's my experience anyways, as a guy who's burned out some barrels.

 

[HSmithTX]

Worn out is a huge span, I have a '38 turk mauser that the bore is beyond awful and the throat is GONE, from rust or shooting or both I don't know but I suspect it's both. It still shoots minute of opposing army soldier easily at 100 yards and if you could get 2-3 of them fairly close together I think you could probably call it 250-300 yards? Benchrest guys will pull barrels that are still shooting 1/4 min or less. Everyone else is somewhere between. My guess for most here on LRH is somewhere around 3/4 to 1 minute is a toasted barrel. A 308 will shoot great with .150" of throat erosion where a 28 Nosler or a 300RUM won't. I don't think there is a number, hit this number and it's done. I think there probably is a number for this cartridge shooting that bullet, plus or minus maybe 30 thousandths. But change bullet or cartridge and I think that number changes.

 

[Rich Coyle]

Gentlemen,
This is a real eye opener. Thanks for the input.

 

[Huntnful]

On my 28 Nosler, mine was about .375". A 195 berger would no longer even sit in the case neck and touch the lands. The hammer bullets had a much fatter Ogive and allowed me to gain a few hundred more rounds. They actually never shot inaccurately. But my velocities would decrease dramatically like every 30-50 rounds. That's no ********. My starting loads was 83gr. N570 at 3300fps, and by the end I needed 88gr. N570 for 3300fps. The 195's would shred to pieces coming out of the barrel at the end.

 

[dfanonymous]

Actually this is a normal life cycle of a barrel. When it's new, MV will change until it reaches a copper equilibrium.
For those that leave their barrels fouled, the MV will stay fairly consistent around a wide curve of shots.

Then as described above, as the throat erodes, you will notice velocity drop off, and usually there will NOT be a accuracy drop off. Most people will retrue their data, and the new MV is rebaselined.

Then one day, you'll get the fliers and it won't group. Then congratulations, you dun burned out your barrel. So a smith either cuts it back, or you get a new one, either way you end up spending money, on top of the money you spend on ammo that burned the barrel out in the first place.

 

[Rich Coyle]

@dfanonymous,

You made me laugh out loud with your last statement.

 

[AZShooter]

I don't worry too much about the advancing throat wear as the issue but rather a long zone down the barrel that gets fire cracked which ultimately determines when it gets replaced. The quickest I have ruined were a 6mm-284 and a 257 Weatherby right around 1000 rounds. Both were custom barrels.

A bore scope shows the horror show when the barrel is on the end of its life. Not only is there significant fire cracking but there are longitudinal cracks that run parallel to the lands and grooves. The aforementioned barrels had the damaged area running up the bore more than five inches!

Signs the barrel is worn out:
Cleanup takes forever.
Requires multiple fouling shots.
After 3-5 obligatory foulers the barrel is only good for a few rounds before it starts throwing flyers.

 

[parshal]

I've had barrels with no lands for 3" still shoot as they did day one. I honestly don't think there's a number that can be given. When groups open or random fliers start showing up is when the barrel's gone.

 

[Rich Coyle]

I've had barrels with no lands for 3" still shoot as they did day one. I honestly don't think there's a number that can be given. When groups open or random fliers start showing up is when the barrel's gone.

Well then, I guess I will continue playing with my mind at peace concerning barrel wear. At 196 rounds fired, with cooling between every shot with a Magnitospeed Riflekul, there is .051" erosion. I fire hammer Hunter 7mm 131 grain at 3,670 feet per second. Lately the five shot groups are running 2 3/8" or under at 300 yards.