What is the verdict on this barrel?

[baldhunter]

I was shocked when I bore scoped all my magnum rifles.You burn a lot more powder and every round you fire the metal the powder flash contacts gets very hot.If you have ever used a cutting torch you know what I mean.If it gets hot enough it's going to start to melt the steel.All my magnums showed erosion signs,where my 308Win's and 30-06's showed no signs The other thing is,if the erosion starts building up,your pressure is going to go up too.I have a 300WSM that was always a little short on freebore from the start.As the erosion started creeping up,I started experiencing loss of accuracy and pressure signs.This rifle could never be loaded up to book max,in fact I had to use 180gr data for 165gr loads.Velocity was there,but with less powder.I ran 20 of the Tubb's fire lap bullets and it moved my throat .100 forward and dropped the velocity 100fps on my loads.It did clean up the lands a bit and now I should be able to increase the loads up to what the books show for the weight of bullets I am shooting.I haven't been back to the range yet,but it's going to require new load work up.I looked at my 7STW throat and didn't take any pictures,but the lands were burnt away in places.The amazing thing is,it still shoots around 1/2".Here is some pictures from my 300WSM.
Before fire lapping



After fire lapping




One of my 300 Win Mags




7mag after about 100 rounds.You can start to see a little erosion starting.

 

[DJ Fergus]

So many variables. I guess thats all you can do is keep an eye on it, and see what its doing. Maybe I get a guicker burn, but what do you mean on a longer barrel? Would that increase the combustion time, giving a more complete burn?
I sure wish I knew what I know now, which is still not much when that STW was brand new. I never imagined I could have that much problem in only 3-400 rounds. One reason I havent worried about it that much.
I didnt develop the load, but it shot well, and I stuck with it.

Ive had problems in the past trying to run powders that are to slow for the length barrel I had. They got powder fouled very bad & quick. I'm assuming that same situation can contribute to carbon build up, especially with ultra overbore case capacities like the stw & 300 Norma. That is just my theory. With those big ultra sized cases, I think 28 inch or more is going to be an all around better choice with a powder burning as slow a n570. I'm guessing that those same cartridges in a 26" will be all around better with something faster like h1000 or retumbo so that it's a better chance of most of the powder burning up before the bullet exits the barrel. I base this off of nothing more than what I have worked with. Other people's findings may be different. I tried running retumbo in a 24" 25-06 and come to the conclusion that it was so slow for that barrel length and that it fouled up alot quicker than I preferred. I really like retumbo alot, but for me it wasn't a good match for that rifle due to fouling.

 

[Tidesloe]

I have a 22 creedmoor that has about the same number of rounds through it and the firecracking in it looks about like that. I shoot 88gr bullets around 3200 FPS out of it. I think the cost of moving heavy-for-caliber bullets fast is barrel life.

True statement. I didnt realize it could be quite that bad though.

 

[MNbogboy]

True statement. I didnt realize it could be quite that bad though.

These bore cams will bring out the OCD in a lot of us. For those of us who have some button rifled factory barrels, it is hard to imagine how the bullet can even make it out the end of the barrel without reducing its caliber!
My guess is you will be fine for a few more years as long as that accuracy holds.
The 2-3 year old ammo may be part of the pressure increase. As Mram10us mentioned try seating a bullet deeper, when it starts to move my guess it will let go with a audible pop or snap.
When you get to the range also try the old & some newly loaded ammo as a comparison.
Good shooting.

 

[Tensilon]

Was going to send you my thoughts last night but I didn't want to rain on your rifle barrel... Here is what I typed and left without sending.
I have been using a Hawkeye for years. Looks like heat cracking in there to me... If it was my barrel, I would not be afraid to try and smooth it up with a delaminated maroon 3M pad wrapped around a worn bore brush to keep it tight in the throat. Then smooth it up a little with a 4x2 cloth and a light polishing of JB. Short stroke it, only about the first 3 inches of the throat. Clean the polishing residue out with swabs wetted with brake cleaner. I generally smooth up the throats on my rifles after about 100 rounds or so with 10 real short strokes of the maroon pad just to keep the pores of the steel closed in the throat area only. This may sound antithetical to making your throat last longer....but by keeping the throat polished it will keep cracking and general wear to a minimum. I'm not telling you to grind off the surface or increase the throat diameter... just try and smooth it up. 3200 fps is pretty cooking for that round. Your mileage on this might vary, but it looks to me like your barrel is well along the way. Bear in mind, others may disagree with what I do, but it seems to keep my throat loss at bay to the point of being surprising. On the other hand if it is still shooting 0.5 MOA...then life is good.
Good luck with your rifle....
Tens

 

[DJ Fergus]

These bore cams will bring out the OCD in a lot of us. For those of us who have some button rifled factory barrels, it is hard to imagine how the bullet can even make it out the end of the barrel without reducing its caliber!
My guess is you will be fine for a few more years as long as that accuracy holds.
The 2-3 year old ammo may be part of the pressure increase. As Mram10us mentioned try seating a bullet deeper, when it starts to move my guess it will let go with a audible pop or snap.
When you get to the range also try the old & some newly loaded ammo as a comparison.
Good shooting.

I believe what you mentioned about the 2 year old loaded ammo can happen alot of times. I've heard of this before. I don't think it's as noticable in most factory ammo for a couple of different reasons but when handloaded is already near max & bullets cold weld to the brass is when that will show up.

 

[wonderman4]

All the pictures shown in this thread just show normal wear & tear for an over bore cartridge. You gotta expect it. I would never use an abrasive such as JB or any other abrasive. All you will do is ruin what barrel you have left. The cracked areas are flame hardened and much harder than the rest of the bore, so an abrasive will only wear the softer steel down, which you don't wanna do.

As another poster mentioned, on rifles such as these, the barrels are considered consumable. Use it up, throw it away, and get another one......then the cycle starts all over.

 

[Tidesloe]

These bore cams will bring out the OCD in a lot of us. For those of us who have some button rifled factory barrels, it is hard to imagine how the bullet can even make it out the end of the barrel without reducing its caliber!
My guess is you will be fine for a few more years as long as that accuracy holds.
The 2-3 year old ammo may be part of the pressure increase. As Mram10us mentioned try seating a bullet deeper, when it starts to move my guess it will let go with a audible pop or snap.
When you get to the range also try the old & some newly loaded ammo as a comparison.
Good shooting.

Thanks, I will do. I get your point on the OCD.
What I didnt know before scoping didnt really seem to be hurting me, other than the increased pressure

 

[bigngreen]

Welcome to the wonder that is N570 and over bore magnums!! My 28 Nosler isn't that bad at about the same level of rounds pushed hard, I do a little throat maintenance every 75-100 rounds and it's cracked but smooth so it's moving but I have not seen odd pressures or velocity changes though I have to chase lands a little. It's amazing the difference you will see when using the exact same case but just going up to 30 cal!!

 

[Bruce Treloar]

It's stuffed, look at all that heat cracking, time to buy yourself a new present.

 

[Tidesloe]

Welcome to the wonder that is N570 and over bore magnums!! My 28 Nosler isn't that bad at about the same level of rounds pushed hard, I do a little throat maintenance every 75-100 rounds and it's cracked but smooth so it's moving but I have not seen odd pressures or velocity changes though I have to chase lands a little. It's amazing the difference you will see when using the exact same case but just going up to 30 cal!!

Yes, these obviously arent your "everyday shooters".
Would you mind sharing a little detail on "throat maintenance"?
I have another question for you bigngreen.
Im about to embark, and nearly ready to begin on a journey involving a cartridge that I know you have been involved in from the start of development and testing. Do you mind if I come to you with some questions on it, once I begin? Ill also be in touch with the creator, and developer on it.
Thanks!!

 

[Tensilon]

What I described to you...is throat maintenance... polishing up the throat. Better if you do it to some degree about every 100 rounds or so. Yours is in fairly rough shape therefore I would work it over with the 3M pad. As I also said some folks might disagree with what I do but clearly there are many out there that have no idea that they can do things to mitigate throat wear to some degree.
Tens

 

[Tidesloe]

Was going to send you my thoughts last night but I didn't want to rain on your rifle barrel... Here is what I typed and left without sending.
I have been using a Hawkeye for years. Looks like heat cracking in there to me... If it was my barrel, I would not be afraid to try and smooth it up with a delaminated maroon 3M pad wrapped around a worn bore brush to keep it tight in the throat. Then smooth it up a little with a 4x2 cloth and a light polishing of JB. Short stroke it, only about the first 3 inches of the throat. Clean the polishing residue out with swabs wetted with brake cleaner. I generally smooth up the throats on my rifles after about 100 rounds or so with 10 real short strokes of the maroon pad just to keep the pores of the steel closed in the throat area only. This may sound antithetical to making your throat last longer....but by keeping the throat polished it will keep cracking and general wear to a minimum. I'm not telling you to grind off the surface or increase the throat diameter... just try and smooth it up. 3200 fps is pretty cooking for that round. Your mileage on this might vary, but it looks to me like your barrel is well along the way. Bear in mind, others may disagree with what I do, but it seems to keep my throat loss at bay to the point of being surprising. On the other hand if it is still shooting 0.5 MOA...then life is good.
Good luck with your rifle....
Tens

Thanks! Yea it actually does make sense to increasing throat life, or maybe a better way to put it is minimizing the damage done.
I would still be a little apprehensive, though with a scope maybe I can take it slow and easy and see if Im gaining on it, or doing more harm than good. This could also be my experimental "practice" barrel too. Too many times Ive gotta screw something up to learn anything, and begin doing things in a way that might be of benefit. Many things Ive learned the hard way. Some came at much expense when first learning what not to do.

 

[DJ Fergus]

Thanks! Yea it actually does make sense to increasing throat life, or maybe a better way to put it is minimizing the damage done.
I would still be a little apprehensive, though with a scope maybe I can take it slow and easy and see if Im gaining on it, or doing more harm than good. This could also be my experimental "practice" barrel too. Too many times Ive gotta screw something up to learn anything, and begin doing things in a way that might be of benefit. Many things Ive learned the hard way. Some came at much expense when first learning what not to do.

Same goes for a good majority of us on here about learning the hard way. I think we've all had some of that.