Thread: Throat Erosion - New Barrel

So update to all of this:
Gave the barrel a mother of a clean and did get some carbon out; whether it was enough to cause inaccuracy or not Im not sure.
Loaded up 4 x 4 shot loads - 3 with 130 Gr ELD-M's seated at 40 thou, 30thou and 20 thou
Then 1 x 4 shot load with 129 Gr LRAB's, also seated at 40thou
Put the target up at 100 yds, bearing in mind that its zero'ed at 200
All bar the 30thou group varing from .4 to .75 inch, with the 20 thou group at just under .4
Results as follows":

Originally Posted by Puffin

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?

Almost certainly the cause of the large initial jump in CBTO distance. Not uncommon to see then the CBTO measurements settle down dependant upon the cartridge and load being fired.

Carbon build up/ring gives the opposite to what the OP has posted ie gives reduced CBTO distances. That's not to say the carbon and maybe copper isn't the cause of the accuracy drop off. The carbon build up also makes it virtually impossible to get repetitive accurate CBTO measurements if using the Hornady case method.

Best to deal with carbon at each clean rather than letting it get a hold.

i see you guys talking about autosol to polish bore can you use brasso

Who knows but why would you bother when Autosol is so readily available/ inexpensive?

Getting OT here but reminds me of my young days when I had a mate whose father was a farm manager. His father had the classic cut down 303 which hung on its sling on a hook on the back of the wash house door. His father told us stories of amazing long range kills taken with this 30.

One day whilst mate’s parents were in town we got the 30 down intending to test it’s accuracy. The bore was a total black hole so we decided to clean it first. We used brasso. We cleaned and cleaned but eventually gave up. Did the old 30 bullet test in the muzzle and is dropped in right up to the brass.

Fired it at 50 yards and only a few shots hit the target and those were all going sideways.

Returned it to its home on the back of the wash house door. Said nothing to father.

I don’t think the brasso killed it just hurried up it demise.

my lesson . . its not your Best group that shows the true potential, its your worst.

Originally Posted by rossi.45

my lesson . . its not your Best group that shows the true potential, its your worst.

I hear what you're sayin , and usually all you get is a one, maybe two shot group if you're lucky.
Always a worthwhile exercise knowin where the hole is likely to be though

Originally Posted by 6x47

Who knows but why would you bother when Autosol is so readily available/ inexpensive?

Because i have a bottle of brasso here and would have to buy the autosol so brasso would be the inexpesive option here

Excellent on removing copper, very mildly abrasive too I've used it on a few old 303 barrels to Polish up the pitting and traces of rifling

Originally Posted by Puffin

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

Greetings Puffin,
My son had the same experience of an apparent erosion of the leade after a small number of rounds in a 7mm-08. We put it down to an initial smoothing up from the early shots. Still shot the same.
Regards Grandpamac.

Originally Posted by northdude

Because i have a bottle of brasso here and would have to buy the autosol so brasso would be the inexpesive option here

Well fill ya boots and report back in a few months on what the borescope/target tells you. Who knows, might even work.

Originally Posted by small_caliber

It seems no one has considered that a carbon wrapped barrel has had the diameter of the metal part of the barrel reduced, therefore the steel part of the barrel will heat up quicker.

Does anyone know the heat coefficient property of Carbon Fibre?


Is the Carbon Fibre trapping the heat in the metal part of the barrel or is it removing the heat?
Has anyone done a test on this?

If the heat is being trapped in the steel part of the barrel then how will this affect throat erosion?

Google proof reasearch barrels.

Done properly carbon wrapped barrels outlast plain steel.

I dont know how hardys are made.

Originally Posted by shooternz

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.

Every new barrel I get has a quick touch up with Autosol, whether brand new or used. The only exception being my Bartlein, which are factory lapped. My rifles all get the Autosol treatment every 200 rounds. An old brush with an Autosol soaked patch wrapped around it is pushed back and forth through the throat area 20 times and 10 times through the remainder less the last couple of inches. I am convinced this slows erosion and it also makes copper removal much easier.

Originally Posted by Bos

Always a worthwhile exercise knowin where the hole is likely to be though

totally @Bos ya gotta know where that bullets going to land . . . some shooters seem to struggle with it. Could be helpfull if shooters stop concentrating on getting that great group and look at the POI more. If you draw a vertical line thru the target center of some of the groups you'll see, some will fall at 10 oclock, some at 2 0clock, a few at 12 oclock, others low . . that 1/2 MOA shooter with the little groups is more like 1 MOA or 2MOA.
The British military had a practice i liked when i first saw it . . called something like Dispersion, you measure the bullet holes from the center of the target not the group size . . cant see that being popular tho, shooters would have to be honest about their abilities
If you get into LR Varminting like some of my shooting is you soon realise that tiny groups are meaningless if you cant put those bullets into a small target on demand at longer range. i like using a 1/2 inch square at 100yrds, if you can put those bullets inside the target you've got a real .5MOA setup & you can move out further, if there wide of the mark you have work to do.
its stopped raining so ramble over . . R

Originally Posted by northdude

Because i have a bottle of brasso here and would have to buy the autosol so brasso would be the inexpesive option here

You could use tooth paste it is a pretty good polish, All depends the size of the abrasive grit how long it will take to get the desired finish,
I knew a Full bore shooter swore by Jif as a barrel cleared.