Barrel erosion?

[mudygmc]

Hey guys, I just picked up a bore scope. Got a couple rifles I'm curious about. Just wondering if you guys know of a good source for info on barrel erosion. Curious to try and understand exactly what im looking at what it means and solutions. Just a couple of examples. My 338 lapua kind of looks like cracked clay or a partially burnt log. It appears to just be on the lands. The rifle still shoots under .5moa so not a big deal yet. My 22creed is running right at .5moa. There is a gracious forming at the start of the bore and lands are flat for a bit. I just got the scope so I dont know what they looked like new. I assume the radious and smooth lands is the beginning of throat erosion. Right at 400rds through it and they have been hot. So I'm fine with that. I mainly got it to check a couple rifles I am having accuracy issues with and to get a feel for proper bore cleaning. Just noticed these two things on the first rifles i picked up. My internet is terrible here. So kind of curious if there was a good book on the subject. But I will take any info as I'm just starting to play with the bore scope and have little knowledge on the subject.

Thanks,
Adam

 

[sedancowboy]

If you search around the internet you will find examples of fire cracking which looks like the Burnt log you described. All barrels are wearing out with each shot. It just depends on the conditions for which it is shot. Fast and hot and you need to order barrels by the 6 pack. Over bores are much worse than say a 308 win. I personally own several hot rods but I don't shoot them until they get hot nor do I run over pressure. They will last me years with good care. I usually say be proud if you get to shoot enough to wear a barrel out.

 

[mudygmc]

If you search around the internet you will find examples of fire cracking which looks like the Burnt log you described. All barrels are wearing out with each shot. It just depends on the conditions for which it is shot. Fast and hot and you need to order barrels by the 6 pack. Over bores are much worse than say a 308 win. I personally own several hot rods but I don't shoot them until they get hot nor do I run over pressure. They will last me years with good care. I usually say be proud if you get to shoot enough to wear a barrel out.

Is it really a hotrod if you take it slow and dont push it. Just messing with ya. I push mine to the fastest accuracy node. I understand the fire cracking. I dont have good internet. I only have my cell phone and lots of reading and searching is tough. Thats kind of why a book or video would be easier for me. I always hear shoot a barrel until the accuracy isnt there. Kind of wondering how far barrels will go. Where is the point or condition they are beyond load adjustment for accuracy. When is it time to throw in the towel and rebarrel. Do bigger bore fire crack and such worse than smaller bores? Just looking for some info on the subject. I use my guns no doubt. I try and respect them but if its 90 out and I have prairie dogs running all over I'm not going to wait the 10min for the barrel to cool. A shot or 2 a minute is going to happen. Like I said my guns are my toys or I guess youd say hobby. They are going to cost money no doubt. I am fine if a barrel only lasts a year or two. Odds are I had a blast tearing it apart. I'm religious on cleaning too. I hear storues about over cleaning a barrel. Kind of wanted to see progress as i clean and how much i really need to do and where.

My main reason for getting a bore scope was for my cousins rifle. He has a win mod 70 7rm he got from his dad who passed away. For the life of us we can get it to shoot a 1moa group. I wanted to look at the bore and see where we stood. We have tried most Other measures with the rifle. Stock was rubbing the barrel on the left side. We opened up the channel and bedded the action. Installed new talley rings and new scope. Cleaned the barrel every night for 2 weeks straight. Seemed spotless. New brass, 5 different bullets 140-180gr 3 different powders. The rifle is all over the target. Nothing at all is consistent. Get close to 1moa. Load 3 more and they are 3moa. Never had a rifle do that. I want to see if the barrel is ok or if we need more testing. He really wants to shoot a mule deer in MT with it. His confidence is a bit low with it now though. Any ideas on this too would ve great

Adam

 

[Mikecr]

The only use for my borescope w/resp to accuracy is seeing that I got all the copper out.
Most barrels do not wear out, as they're replaced far in advance of something like that.
The lands are heated, surface opened, to a point where each shot can knock away tiny bits (erosion). Some would see this as wearing (I don't). But this only hurts accuracy if your load is reliant on chasing lands, and you're not keeping up with tested land relationship, along with powder & tension adjustments to do that..

What kills accuracy is carbon constrictions. This follows accumulations as the metal surface opens to let carbon work it's way in. The surface opens most where it's hottest.
It can be slowed via regular & rational application of an abrasive (like JB non-embedding bore compound) during cleanings. At some point this will no longer work and instead accelerate bore damage (it begins to break more bits off). Stubborn folks may decide then to set a barrel back for a few hundred more accurate shots.. I say you should have had a new barrel in waiting by then.

Another reason I suggest that our tossed barrels didn't wear out, is because we could if we chose to, set back a barrel far enough to practically start over, because 5-10" down the bore the surface was never opening enough to let carbon in. That is, unless you allowed the barrel to get hot enough for that, and rarely cleaned the bore*.
That said, it is entirely possible to wipe out a barrel in one shooting session (I've seen this).

Anyway, you don't normally see the carbon that is killing accuracy. But you can often feel it while pushing tight patches through the bore.
*One example where you can see it is with use of moly. This condenses further down the bore, and is wiped in layers to form a ring that is both visible and felt with patches. By the time you get there with it, the efforts to fix that bore will also destroy it. Game over.

There is another method of managing all this: Tubb's TMS

 

[Rick Richard]

Fire Cracking is a normal process in the life of a barrel. Every barrel is different as to when it will occur, but I find it to begin within the the first @30 % there about of a barrels life. Now, how long before it effects accuracy? I can't answer that so I shoot until the accuracy goes away for my liking.

 

[AZShooter]

I wish I had a hawkeye long ago to solve some mysteries. Have one now and can report that a Bartlein 5R 6mm-284 1 in 7.5 twist shooting 105s @ 3475 fps and the 257 Weatherby Lilja 3 groove 1 in 10 twist shooting moly coated 115 VLDs @ 3680 fps both developed issues right around 1000 rounds. I experienced difficult cleaning, requirement of several fouling shots with first few foulers WAY off POI at 100 yds. Both would shoot great after the foulers for ten rounds or so then open up. Got tired of repeating the long cleaning session with a short accuracy window. I considered them worn out.

Bore scope inspections showed both barrels had the firecracking you mentioned AND long longitudinal cracks running up the bore for well over 8". For grins I cut off 6" from the Bartlein 6mm-284 and machined it again for 6mm-284. Much to my amazement it shoots once again, I don't expect it to last very long but it was a free experiment as I have a lathe.

I cannot help with suggestions on places to look or for reading material. You could go to your gunsmith's and look at barrels that were pulled. Be sure to look at every rifle new and used you can get your hands on too. Inspect throats to see if every land starts at the same place in the throat, some don't. See if you can see lumps of copper fouling, bad crowns or even missing lands. That exposure will teach you a great deal.
You can even look at the insides of a cartridge.

 

[Mikecr]

AZShooter, would you share your powder loads for these two cartridges?
PM if concerned about it

 

[Lefty7mmstw]

I've seen it both ways. I've got a remmy lh bdl in 300rum that I've had to JB the heck out of to get it to stop fouling in just a few shots. The rifle's throat is starting to fire crack and will never be bright and shiny again. It, however, will still run .5 to .6 moa with a 225 at 3K fps. I'd be surprised if she lasts more than another couple hundred shots.
I've eroded the rifling flat for the first few inches on two 7rum rifles and a 243 and all three showed little to no fire-cracking. The last 7rum barrel (from a lh lss) is still sitting in my shop; she shot cloverleafs until she decided one day to start tossing errant shots. The first 7rum (rh bdl)I shot out simply started shooting bigger and bigger groups; a look down the barrel showed a flattened throat. The 243 was a savage pistol that decided to stop shooting. I hadn't really bothered to peek down the barrel but again, she had almost no rifling for the first few inches. All three looked glass smooth with basically no fire cracking.

 

[Greyfox]

I have been using s Lyman bore scope to monitor my barrels for a few years. Great investment! Very useful for monitoring bore condition and the cleaning process. I make it a point to check my barrels BTO standard measurement and bore condition. Mild to moderate cracking with most all my barrels under normal shooting conditions seems to develops in the free bore portion of the barrel very soon, within a few hundred rounds. This appears to be normal. High volume and shooting hot will show the more severe fire cracking progressing into the rifling. Even with this happening, the barrels BTO measurement(distance to the lands)can remain unchanged, and accuracy held. Accuracy can begin to fall off when the rifling is worn to the point when the BTO measurement starts to increase and/or the fire-cracking progresses down the bore and gets to the point where the lands begin to fragment. The latter seems to occur with frequent "hot" shooting. With normal shooting, not allowing the barrel to get overheated, the rifling just smooths out with the BTO continuing to increase. Some barrels/loads can loose accuracy with as little as a .010" erosion, others can hold much longer. Chasing the lands can prolong barrel life but the end is generally near. IMO.

 

[Deleted member 25294]

I've seen it both ways. I've got a remmy lh bdl in 300rum that I've had to JB the heck out of to get it to stop fouling in just a few shots. The rifle's throat is starting to fire crack and will never be bright and shiny again. It, however, will still run .5 to .6 moa with a 225 at 3K fps. I'd be surprised if she lasts more than another couple hundred shots.
I've eroded the rifling flat for the first few inches on two 7rum rifles and a 243 and all three showed little to no fire-cracking. The last 7rum barrel (from a lh lss) is still sitting in my shop; she shot cloverleafs until she decided one day to start tossing errant shots. The first 7rum (rh bdl)I shot out simply started shooting bigger and bigger groups; a look down the barrel showed a flattened throat. The 243 was a savage pistol that decided to stop shooting. I hadn't really bothered to peek down the barrel but again, she had almost no rifling for the first few inches. All three looked glass smooth with basically no fire cracking.

Do you know how many rounds you've put through your 300 RUM?
I'm trying to get an idea of how long I should expect my 300 Norma Mag to last

 

[mudygmc]

I appreciate the info. I looked at my oldest 223 ar15 last night. The barrel has between 17-18,000 rounds through it now. Nothing crazy hot 90% has been 55gr at 3,000fps or 68s slower don't remember the speed. I was religious on cleaning the rifle after ever use. The accuracy is still there with quality ammo. 1/2-5/8 on a good day. It was a 1/4 rifle in its prime. The bore wasn't what I was expecting. There was fire cracking for 8-10in. The lands were virtually smooth for 1.5-2in. Bore is smooth and shinny. Not much pitting or cracks further down. The gas port surprised me. It was almost perfect yet. Slight radious but not eroded much if any. This was my first time ever looking down this barrel. Are more mild cartridges more forgiving towards barrel wear vs more hot rodded loads. This rifle has shot steel and paper for days. And the amount of time in dog towns is weeks. But after a good cleaning 5-10 fouling shots the 55gr vmax are still at .5moa. The pics I've seen of had port erosion I assume has to be from crazy amount of rapid fire shooting or is it back to a hot load or a combo. Like i said i hear stories of barrels sjooting out. Just trying to get a feel for what is going on. I know each is different and my 223 might be a fluke. Just wondering if there is some common guidelines to what happens. I will keep studying and taking notes on my barrels. Especially the magnums I push hot. I'm glad I finally purchased a bore scope. Just wish I understood it a bit more.

Adam

 

[Greyfox]

I appreciate the info. I looked at my oldest 223 ar15 last night. The barrel has between 17-18,000 rounds through it now. Nothing crazy hot 90% has been 55gr at 3,000fps or 68s slower don't remember the speed. I was religious on cleaning the rifle after ever use. The accuracy is still there with quality ammo. 1/2-5/8 on a good day. It was a 1/4 rifle in its prime. The bore wasn't what I was expecting. There was fire cracking for 8-10in. The lands were virtually smooth for 1.5-2in. Bore is smooth and shinny. Not much pitting or cracks further down. The gas port surprised me. It was almost perfect yet. Slight radious but not eroded much if any. This was my first time ever looking down this barrel. Are more mild cartridges more forgiving towards barrel wear vs more hot rodded loads. This rifle has shot steel and paper for days. And the amount of time in dog towns is weeks. But after a good cleaning 5-10 fouling shots the 55gr vmax are still at .5moa. The pics I've seen of had port erosion I assume has to be from crazy amount of rapid fire shooting or is it back to a hot load or a combo. Like i said i hear stories of barrels sjooting out. Just trying to get a feel for what is going on. I know each is different and my 223 might be a fluke. Just wondering if there is some common guidelines to what happens. I will keep studying and taking notes on my barrels. Especially the magnums I push hot. I'm glad I finally purchased a bore scope. Just wish I understood it a bit more.

Adam

Curious if your 223 barrel mentioned above is chrome lined?

 

[Lefty7mmstw]

Do you know how many rounds you've put through your 300 RUM?
I'm trying to get an idea of how long I should expect my 300 Norma Mag to last

I bought it used with a few hundred rounds on it. I've put another 400-500 rounds through it and as said before it still shoots but the bore is showing signs of tiring. I'd say she'll die with a bit over 1200 rounds through her. I now have a remmy lr in 300rum also so I doubt I'll be putting rounds through it quickly.
By comparison, my browning lh ss 300win has north of 1200 rounds on it already, and though she now takes a few foulers to start shooting straight, it doesn't show serious visual rifling wear.

 

[Lefty7mmstw]

I appreciate the info. I looked at my oldest 223 ar15 last night. The barrel has between 17-18,000 rounds through it now. Nothing crazy hot 90% has been 55gr at 3,000fps or 68s slower don't remember the speed. I was religious on cleaning the rifle after ever use. The accuracy is still there with quality ammo. 1/2-5/8 on a good day. It was a 1/4 rifle in its prime. The bore wasn't what I was expecting. There was fire cracking for 8-10in. The lands were virtually smooth for 1.5-2in. Bore is smooth and shinny. Not much pitting or cracks further down. The gas port surprised me. It was almost perfect yet. Slight radious but not eroded much if any. This was my first time ever looking down this barrel. Are more mild cartridges more forgiving towards barrel wear vs more hot rodded loads. This rifle has shot steel and paper for days. And the amount of time in dog towns is weeks. But after a good cleaning 5-10 fouling shots the 55gr vmax are still at .5moa. The pics I've seen of had port erosion I assume has to be from crazy amount of rapid fire shooting or is it back to a hot load or a combo. Like i said i hear stories of barrels sjooting out. Just trying to get a feel for what is going on. I know each is different and my 223 might be a fluke. Just wondering if there is some common guidelines to what happens. I will keep studying and taking notes on my barrels. Especially the magnums I push hot. I'm glad I finally purchased a bore scope. Just wish I understood it a bit more.


Adam

If the accuracy is still there continue to shoot it, condition be damned. The thing isn't dead 'till the accuracy craps out or she fouls badly or starts pressuring up from a rough throat.