Thread: Throat Erosion - New Barrel

So a couple of comments.

Were you shooting from a machine rest, or is it possible you just had a bad day ? How consistently did you get your 0.4 inch groups previously.

10 thou erosion for on;y 200 rounds is pretty harsh, even for throat burner like 6.5-06 / 6.5x284

How are you you getting getting your lands measurement. It is notoriously difficult to get repeatable / consistent lands measurements.

Originally Posted by GWH

Going from .4 inch to 4 inch after 200 rounds, id also suggest its a carbon problem, as ive experienced similar big change in grouping, and after trying everything else to no avail, polishing out the carbon got me back to .5 moa.

Get some autosol on a patch and polish it back and forth, focus on one third of the barrel length at a time, just be careful you dont pull it back thru the muzzle.

You could change the patch for each third and add more autosol polish on each one.

Then after polishing give it a normal clean with your normal chemical to flush out the polish and carbon residue.

Id try this first and test shoot.

That sounds like a lot of hard work

https://youtu.be/xte_pf3ZhsA

Originally Posted by dannyb

That sounds like a lot of hard work

https://youtu.be/xte_pf3ZhsA

Yeah seen it and tried it on a very heavily carbon fouled barrel on a 2nd hand rifle i'd purchased.

Originally Posted by GWH

Going from .4 inch to 4 inch after 200 rounds, id also suggest its a carbon problem, as ive experienced similar big change in grouping, and after trying everything else to no avail, polishing out the carbon got me back to .5 moa.

Get some autosol on a patch and polish it back and forth, focus on one third of the barrel length at a time, just be careful you dont pull it back thru the muzzle.

You could change the patch for each third and add more autosol polish on each one.

Then after polishing give it a normal clean with your normal chemical to flush out the polish and carbon residue.

Id try this first and test shoot.

JBs is fine but please please not autosol!!

If you already have a good cleaning regime,maybe a look down with a bore scope will confirm this. Talk to some fullbore shooters they may have access to one..... with JB compound dont try and polish all the black stuff off the cloth..... thats metal! Hope it all comes good.

Common old CLR (Calcium, Lime, Rust remover at $20 for a lifetime supply from the hardware store) will take out carbon from barrels without any ill effects - the last thing you want in the barrel of a rifle with the throat being eroded is more abrasive like JB paste . . .

As and example - I used it on an Annie 22 that looked to have a perfect bore but wasn't shooting that well - it produced a prodigious amount of carbon and the rifle is again a tack driver.

Watch the Eric Cortina video on it . . . . https://www.youtube.com/watch?v=xte_pf3ZhsA

I have a Hardy barrel on my 300saum as well. About 300 full noise loads with N550 & R17 and no drop off in accuracy. Has always held around .75moa sort of average. Good bore clean about every 50 shots and a dry bore snake after each hunt. Has never had a copper problem.

Originally Posted by ebf

So a couple of comments.

Were you shooting from a machine rest, or is it possible you just had a bad day ? How consistently did you get your 0.4 inch groups previously.

10 thou erosion for on;y 200 rounds is pretty harsh, even for throat burner like 6.5-06 / 6.5x284

How are you you getting getting your lands measurement. It is notoriously difficult to get repeatable / consistent lands measurements.

Yeah id expect 10 thou throat erosion per 100-200 rounds on something like a 26 nosler where theres a huge amount of powder, but it certainly sounds excessive for a 6.5-06. If that is the case (and not just a measuring mistake) i wonder if the barrel material could be 'softer' than normal?

Anyway, just seat you bullets longer to test grouping to find the new oal it likes and shoot away, and periodically test grouping at a few thou longer every couple of hundred rounds.

Originally Posted by omark

JBs is fine but please please not autosol!!

Why? JBs is more aggressive than Autosol.

I'll tell you a little story about Autosol. My NRA target rifle had a 30" Krieger bbl and it shot moly'd 155 Sierras with great accuracy at 2950. Here was the cleaning regimen that never varied. With a patch wrapped round a worn .270 brush, Autosol was lathered on and run back and forth through the bbl for 8-10 strokes. Repeated this, then wiped out with a clean patch. At over 3000 rounds, we had a look with a borescope and there was no visible rounding off of the lands and the bore was bright and squeaky clean. At a documented 5000 rounds, I decided to shoot it over a benchrest as I suspected it might have gone off the boil. It produced a 5-shot group of sub half inch. The accuracy finally went to pieces about 400 rounds later but you'd be hard pressed to convince me the barrel was ruined by Autosol.

It was in fact Steve Blenkarne ( the orig owner of Truflite) that suggested it to Tony Halberg and I adopted the method. Steve used it all the time apparently.

Originally Posted by 6x47

Why? JBs is more aggressive than Autosol.

I'll tell you a little story about Autosol. My NRA target rifle had a 30" Krieger bbl and it shot moly'd 155 Sierras with great accuracy at 2950. Here was the cleaning regimen that never varied. With a patch wrapped round a worn .270 brush, Autosol was lathered on and run back and forth through the bbl for 8-10 strokes. Repeated this, then wiped out with a clean patch. At over 3000 rounds, we had a look with a borescope and there was no visible rounding off of the lands and the bore was bright and squeaky clean. At a documented 5000 rounds, I decided to shoot it over a benchrest as I suspected it might have gone off the boil. It produced a 5-shot group of sub half inch. The accuracy finally went to pieces about 400 rounds later but you'd be hard pressed to convince me the barrel was ruined by Autosol.

It was in fact Steve Blenkarne ( the orig owner of Truflite) that suggested it to Tony Halberg and I adopted the method. Steve used it all the time apparently.

Yep i agree, the autosol treatment was also first recommended to me by a very experienced top target shooter too, i'll keep using it, as it works. I've tried the CLR on one problem barrel i have here and it left some strange marks in the surface of the bore, i think ill be leaving that stuff for Eric.

Your original reference CBTO measurement for just touching might have been influenced by some roughness in the finish of the cut of the leade, that has now been smoothed out after some shooting and hopefully has stabilised. The improvement in copper fouling might support this idea?

I had something that seems similar recently in a set-back 6.5x47 chamber; 0.2mm (0.008") lengthening after 150 rounds, and initially with significant copper fouling when the barrel had always shot clean for 1700 rounds prior with the original chamber. Opened out the groups too — to a degree, but as we all know, a 6.5x47 never shoots more than half-inch even in the most adverse circumstances, so difficult to compare

Originally Posted by 6x47

Why? JBs is more aggressive than Autosol.

I'll tell you a little story about Autosol. My NRA target rifle had a 30" Krieger bbl and it shot moly'd 155 Sierras with great accuracy at 2950. Here was the cleaning regimen that never varied. With a patch wrapped round a worn .270 brush, Autosol was lathered on and run back and forth through the bbl for 8-10 strokes. Repeated this, then wiped out with a clean patch. At over 3000 rounds, we had a look with a borescope and there was no visible rounding off of the lands and the bore was bright and squeaky clean. At a documented 5000 rounds, I decided to shoot it over a benchrest as I suspected it might have gone off the boil. It produced a 5-shot group of sub half inch. The accuracy finally went to pieces about 400 rounds later but you'd be hard pressed to convince me the barrel was ruined by Autosol.

It was in fact Steve Blenkarne ( the orig owner of Truflite) that suggested it to Tony Halberg and I adopted the method. Steve used it all the time apparently.

Steve used it to polish his new barrels, he always recommended it.

Carbon build up is something I experienced recently, had been just givving a couple of patches of hoppes then a dry patch every 50 rounds or so but not doing a proper clean, at about the 150 round mark pressure jumped up markedly. A look with a borescope showed a "smeared" looking ring in the throat that required polishing out.
My first overbore cal that is suppressed and the combination of slow powder and suppressor means that now rather than trying to leave carbon in I will be trying to remove it reguarly.
I dont have a starting lands measurment to compare for you unfortunately as it came with developed loads but I do now so will see how it goes from here.

Originally Posted by veitnamcam

Carbon build up is something I experienced recently, had been just givving a couple of patches of hoppes then a dry patch every 50 rounds or so but not doing a proper clean, at about the 150 round mark pressure jumped up markedly. A look with a borescope showed a "smeared" looking ring in the throat that required polishing out.
My first overbore cal that is suppressed and the combination of slow powder and suppressor means that now rather than trying to leave carbon in I will be trying to remove it reguarly.
I dont have a starting lands measurment to compare for you unfortunately as it came with developed loads but I do now so will see how it goes from here.

Try using some patches soaked in CLR ( from likes of Warehouse ) removes carbon real good just dont spill on blued surfaces (not sure on cerekote)
Ive not had any issues with it but never leave it in for more than 30 mins

Originally Posted by tetawa

Steve used it to polish his new barrels, he always recommended it.

Yes he did, I spent a lot of time at Steves place the north shore all his barrels were polished with Auto Sol, He recommend that
barrels were Auto sol'ed when new it helps with copper fouling, It has with my barrels, I saw him run a new barrel in a a championship
match at Te Puke rifle club , fire 10 shots clean at 300 yds repeat at 500 and 600 job done.