Rifling Deterioration?

[Tommy T]

Yeah I could not see the lands at all. It just looked like a shiny blur but it wasn't the camera. Ive been pushing this barrel pretty hard, just kinda surprised me when I saw the image. It showed very little fire cracking and there was more definition in the lands and grooves the last time I scoped it after cleaning, wish I had of clicked a couple of pics now. It's been a good barrel and was a quality one for sure. I've shot out a couple in my life now, I hate that it eventually comes to that, but that's the game. Currently I have my old Sendero at Alamo getting a new one spun up for it.

Alamo Jason and them guys. Build a great rifle , they build me a 30 nosler with a proof barrel that was no good they took it back and I put a Bartlein on it

 

[mray190]

I have a 7 prc and a6.5 prc they both have about 700 hot rounds thru them and they are starting to open up 1/4" to 1-14" groups I think that maybe my problem

If you don't have borescope even a cheaper digital one get one. They will let you see a lot, not as much has the higher end one but you can still see stuff like fouling buildup and carbon rings. My main use for them is just inspection after cleaning to see if I missed anything or if one cleaning regiment is working or not. My sendero when from 1/4"-38" groups to almost 2" groups a long time ago and I thought for sure it was toast. Heavy carbon deposits along with some decent fire cracking were the issue. Some elbow grease and a healthy dose of JB's got it back to shooting again. This pic was from this summer but it's now at the shop getting rebarreled.

 

[mray190]

Alamo Jason and them guys. Build a great rifle , they build me a 30 nosler with a proof barrel that was no good they took it back and I put a Bartlein on it

Yeah man they've helped me many times over the years, from getting gear for work to getting rifles back up and running in record time. They rebarrelled three of my work guns and I can't wait to get my old hunting rig back from them. It was an old gen1 sendero in 25-06. Stayed with the quarter bore but decided to do it in Ackley instead as I have always wanted to mess around with one, plus that case profile looks so cool.

 

[Tommy T]

Yeah man they've helped me many times over the years, from getting gear for work to getting rifles back up and running in record time. They rebarrelled three of my work guns and I can't wait to get my old hunting rig back from them. It was an old gen1 sendero in 25-06. Stayed with the quarter bore but decided to do it in Ackley instead as I have always wanted to mess around with one, plus that case profile looks so cool.

Yeah man they've helped me many times over the years, from getting gear for work to getting rifles back up and running in record time. They rebarrelled three of my work guns and I can't wait to get my old hunting rig back from them. It was an old gen1 sendero in 25-06. Stayed with the quarter bore but decided to do it in Ackley instead as I have always wanted to mess around with one, plus that case profile looks so cool.

Is that a 280

 

[mray190]

Is that a 280

No 257

 

[SSG Graybush]

While the rifling in the photo looks pretty rough, my guess it's likely not that much different then it was before you experienced a loss in accuracy. The section of the barrel that you should be looking with your bore scope is the erosion at the throat, and/or a carbon ring that forms where the free-bore and the rifling begins. It is the heat(fire-cracking), and erosion of the powder burn/bullet entry into the land that causes this wear which migrates with time. Accuracy loss begins with the change in bullet seating depth to the lands. The military has specs for the the amount of rifling erosion permissible at the throat before replacement (ie, .010" throat erosion/1MOA accuracy loss). The other area of barrel wear that can cause an abrupt change in accuracy is at the crown(entry point at the end of the barrel). It can usually be seen with the naked eye. It should be even and square. This damage can be caused by physical contact that damages the crown and/or improper cleaning methods.
What may be cause an accuracy change over time in the main section of the barrel, and observed with a bore-scope, is carbon(carbon slick in the lands), and/or copper build up…..easily seen and can often be removed by cleaning.
When I was competing in rifle competition, I would have to monitor barrel wear, replacing barrels as much as 1-2x per season. Barrels were subjected to high heat in the warm summer months and accuracy/precision demands were pretty stringent.
This cutaway is an example of a shot out barrel. First place to bore-scope the barrel. It has much more than .010" of throat erosion/rifling loss which is about when you should start checking accuracy/precision and about a new barrel…..Or perhaps increasing the seating depth of your bullet to get a little extra accurate barrel life……IMO
View attachment 627930

You ment increase the coal/seat the bullet out further, not increase seating depth. But I got you. Great pic.

 

[AussieWriter]

If you don't have borescope even a cheaper digital one get one. They will let you see a lot, not as much has the higher end one but you can still see stuff like fouling buildup and carbon rings. My main use for them is just inspection after cleaning to see if I missed anything or if one cleaning regiment is working or not. My sendero when from 1/4"-38" groups to almost 2" groups a long time ago and I thought for sure it was toast. Heavy carbon deposits along with some decent fire cracking were the issue. Some elbow grease and a healthy dose of JB's got it back to shooting again. This pic was from this summer but it's now at the shop getting rebarreled.

View attachment 627966

But, looks don't tell the whole story, they just indicate the stage of the journey for your barrel.

I have a barrel right now that is many, many, times worse than any fire cracking anyone has seen on the net for about 2" into the barrel. It shoots way under the inch so I keep shooting it and continue to monitor it.

In the days before bore scopes were common, I shot the barrel out of a .257 Weatherby and also documented every shot over its lifespan.

When accuracy fell off, it was fast, around a 70 round count. The throat wear could be seen with the naked eye as a dirty unclear, undefined area. Dirty looking.

The group size increasing coupled with a round count is a gpod reference point for anyone without a bore scope, though price isn't really an obstacle anymore.

 

[Shankedit]

If you don't have borescope even a cheaper digital one get one. They will let you see a lot, not as much has the higher end one but you can still see stuff like fouling buildup and carbon rings. My main use for them is just inspection after cleaning to see if I missed anything or if one cleaning regiment is working or not. My sendero when from 1/4"-38" groups to almost 2" groups a long time ago and I thought for sure it was toast. Heavy carbon deposits along with some decent fire cracking were the issue. Some elbow grease and a healthy dose of JB's got it back to shooting again. This pic was from this summer but it's now at the shop getting rebarreled.

View attachment 627966

What's an example of a higher end borescope? I've been looking to buy one but kinda get lost in the weeds.

 

[highbrow]

Barrels are consumables like tires. Gotta replace them after a while.

 

[AussieWriter]

Barrels are consumables like tires. Gotta replace them after a while.

Yep. Opens the door to new camberings and more learning too.

 

[WapitiBob]

This is a 7stw using N570 and Berger 195's.
Knowing the powder eats barrels, I measured the throat at 80 shots, then measured again at 432. I burned away .100" of the throat in those last 350 shots, never firing more than 2 then using the chamber chiller. I rarely shoot more than 15 shots in a range session.
At 432 I set the 195's out to the new lands ( 3.275 CBTO ) then pulled back .020". With the extended throat I finally got the boat tail above the case neck/shoulder jct, then I re shot my powder charges to see how bad it was going to be.

This rife has never produced the 3 shot groups seen at 81.5 and 82, which have been replicated. So far, it seems the bullet placement in the case has more influence on this rifles groups than fire cracking and throat erosion.

 

[smkymtnboy]

This is a 7stw using N570 and Berger 195's.
Knowing the powder eats barrels, I measured the throat at 80 shots, then measured again at 432. I burned away .100" of the throat in those last 350 shots, never firing more than 2 then using the chamber chiller. I rarely shoot more than 15 shots in a range session.
At 432 I set the 195's out to the new lands ( 3.275 CBTO ) then pulled back .020". With the extended throat I finally got the boat tail above the case neck/shoulder jct, then I re shot my powder charges to see how bad it was going to be.

This rife has never produced the 3 shot groups seen at 81.5 and 82, which have been replicated. So far, it seems the bullet placement in the case has more influence on this rifles groups than fire cracking and throat erosion.

View attachment 628016

thats interesting!!

 

[spladi]

The revelation of "shot out" for my T3 heavy .223 was that it went from phenomenal accuracy with the Berger 73 and 25.3 Varget to
Shooting like a load I wouldn't even had considered but still shoots the 77great at 100 but not at 200.

 

[pdog shooter]

22-250 2000ish rounds and lots of dead pdogs
mrays barrel looks pretty good to me.