When did copper fouling stop in your barrel.

[Alex Wheeler]

Velocity increase is normal. With advent of the lab radar we have a shooter you has logged the first 150 rounds and counting on 2 barrels now. The velocity curve was interesting, but they always speed up around 100 rounds or so. If you bore scope them, you can see the throat and bore smoothing out some which probably is increasing pressures. The ONLY barrels I have seen not speed up like this are Rock Creek. I do believe it is due to their lapped finish. It does look different than say a Krieger. I recommend no load work be done before 100 rounds or you will chase your tail after the speed up.

 

[Bart B.]

In my chrono sessions, first shot from a clean barrel is ~ 5 - 10 fps slower than the second one, third shot ~ 5 - 10 fps faster than second one. Following shots about the same. This is with Hart, Obermeyer and Kreiger match barrels. Velocity stabilized after 3, sometimes 4, shots.

Regular commercial barrels did the same thing but had greater spreads and took more shots before velocity stabilized. Smooth bore versus rough bore.

 

[butchlambert]

In my chrono sessions, first shot from a clean barrel is ~ 5 - 10 fps slower than the second one, third shot ~ 5 - 10 fps faster than second one. Following shots about the same. This is with Hart, Obermeyer and Kreiger match barrels.

Regular commercial barrels did the same thing but had greater spreads and took more shots before velocity stabilized. Smooth bore versus rough bore.

My experience are all barrels increase in velocity after they are fouled with a couple shots. Alex, how can a conditioned throat create more pressure?

 

[Bart B.]

One more thing......

My barrels needed about a 1 MOA higher sight setting for zero the last 5 to 10 percent of their accurate lives for the same load component suite at long ranges. Bullets left slower than when the barrel was new.

 

[butchlambert]

One more thing......

My barrels needed about a 1 MOA higher sight setting for zero the last 5 to 10 percent of their accurate lives for the same load component suite at long ranges. Bullets left slower than when the barrel was new.

Sounds like you waited too late to rebarrel.

 

[Alex Wheeler]

My experience are all barrels increase in velocity after they are fouled with a couple shots. Alex, how can a conditioned throat create more pressure?

Smoother surface = increased surface area for bullet contact. And its along the tops of the lands too. Thats just a guess at why they speed up. What else changes in a bore during those first 100 except the surface finish? If you chrono a barrel early in its life you will see the speed up occur. Not talking fouling, barrels are cleaned a lot. If you find a load early on you will usually need to pull powder out to get back in tune somewhere around 100 rounds when that speed up happens.

 

[butchlambert]

Smoother surface = increased surface area for bullet contact. And its along the tops of the lands too. Thats just a guess at why they speed up. What else changes in a bore during those first 100 except the surface finish? If you chrono a barrel early in its life you will see the speed up occur. Not talking fouling, barrels are cleaned a lot. If you find a load early on you will usually need to pull powder out to get back in tune somewhere around 100 rounds when that speed up happens.

Alex,
What I am saying is after each group I clean the barrel. I shoot a couple fouler shots before going to the record. The part I can't get my hands around is how a smoother throat builds more pressure.

 

[Bart B.]

↑
One more thing......

My barrels needed about a 1 MOA higher sight setting for zero the last 5 to 10 percent of their accurate lives for the same load component suite at long ranges. Bullets left slower than when the barrel was new.

Sounds like you waited too late to rebarrel.

I don't think so. Accuracy had degraded about 50%, typical of all match grade barrels at their end of life. For example, 1/2 MOA when new, 3/4 MOA at end of life. All barrels' accuracy slowly gets worse over their lives.

I've seen plots of Sierra's test barrels 10-shot QC groups with the same reference lot of ammo. Slower rate in the first half, faster in the last. A 50% accuracy loss was their end of life point as a test barrel. Their 308 Win barrels started out 1/4 MOA or better average when new. At about 50% loss, about 3/8 MOA average, they were replaced; typically at 3000 rounds or thereabouts.

 

[Mtstalker]

A smooth object will always increase friction when left unlubricated, if lubrication is added it will have less friction due to fluid film, this causes no metal to metal due to the evenness of the surfaces. Now when its rough there is what we call rolling friction, this is where the peaks and valleys of the surfaces touch leff friction due to leas surface area touching. To a certain point this will lower friction and then it will increase friction if it is too rough. When you lubricate a rough surface it doesnt do much since there cannot be full fluid film lubriction between the two surfaces. I know it sounds backwards but i see it all the time. If you take two higly polished peices of metal and put 100 pounds on them and try to slide it it will be very jerky do to more surface area. Now if you take two unpolished regular peices that dont have millscale in them and do this one it moves its not a jerky motion. Same concept with racing slicks. More surface contact the more friction.

 

[butchlambert]

I don't think so. Accuracy had degraded about 50%, typical of all match grade barrels at their end of life.

Wow,
If my barrel degraded 10% it would get tossed into the tomato patch or cut off some and rechambered.
The internet has all the answers.

 

[Alex Wheeler]

Alex,
What I am saying is after each group I clean the barrel. I shoot a couple fouler shots before going to the record. The part I can't get my hands around is how a smoother throat builds more pressure.

Butch is just a guess. A coarse lapped finish creates micro grooves and reduces contact area. A smoothed finish will increase surface contact and probably friction which could be the reason for the speed up. I said throat and bore smooths out, I would attribute the speed up to the bore finish not really the throat. I dont give a lot of thought to it as its not important. All I KNOW is, it happens and how to deal with it.

 

[fourpower]

I recently put a shilen match barrel on a savage action. I did there break in yesterday and shot a total of 40 rounds. Its a 260 rem 8 twist and this thing copper fouls like crazy. It shoots good with the factory ammo i used but man it seemed to copper worse and worse. I used boretech eliminator to clean untill no traces of blue was there after a 10 minute soak. After the last 5 round group it took 6 rounds of soak the bore and brush and then soak for 15 min to get it clean. Will this stop at any point? I was under the impression that these are lapped barrels.

I hand lap all my new barrels no matter who makes them and then use bore coat on them! they have always been better for me after that.

 

[butchlambert]

I hand lap all my new barrels no matter who makes them and then use bore coat on them! they have always been better for me after that.

Wow, what does it do for you that the custom barrelmakers lap doesn't do? I'll be away from the computer for an hour or so, but will check back in.

 

[T-shooter]

In my chrono sessions, first shot from a clean barrel is ~ 5 - 10 fps slower than the second one, third shot ~ 5 - 10 fps faster than second one. Following shots about the same. This is with Hart, Obermeyer and Kreiger match barrels. Velocity stabilized after 3, sometimes 4, shots.

Regular commercial barrels did the same thing but had greater spreads and took more shots before velocity stabilized. Smooth bore versus rough bore.

Have you tried that with a fouled cold barrel? Wonder how much if any is due to the metal expanding from heat?

 

[T-shooter]

Alex,
What I am saying is after each group I clean the barrel. I shoot a couple fouler shots before going to the record. The part I can't get my hands around is how a smoother throat builds more pressure.

If the bore is smooth and perfectly clean, there is more surface contact area. My idea, and I could be wrong, is after cleaning run an oily patch through followed by a dry one. A slight oil film will lubricate and foul quicker as it burns off and possibly help prevent coppering on the first shot.

 

[Bart B.]

Have you tried that with a fouled cold barrel? Wonder how much if any is due to the metal expanding from heat?

Yes.

Oft times shooting long range matches at the NRA site near Raton, NM, l would stop by their smallbore range to put 3 fouling shots through each barrel. First sighter and following ones held same elevation average at target range getting windage zero's. Corrected for elevation average then shot first record round for score.

Otherwise, first sighter at 800 to 1000 yards averaged 1/4 to 1/3 MOA below several sighters' group elevation average. I chose not to deal with that.

Barrel steel expands about 5 to 6 micro inch (.000005" to a millionth more) for each degree F of temperature rise. Bullets upset to groove diameter. 25 to 30 shots fired twice a minute has not caused vertical shot stringing in my barrels. Barrel temp. increased 70 to 80 degree F from cold ambient temperature according to my thermal IR thermometer. Bullets must not got unbalanced enough to matter.

I don't keep a chambered round in the barrel more than 15 seconds before shooting it. If it stays in longer, I come down 1/4 MOA on the sight for every 30 seconds a 308 round's in the chamber; 20 seconds for 30 caliber magnums. Hot powder shoots bullets faster. Done that over a dozen times; works well for me.

The NRA High Power Committee has a rule in the book that allows for shooters to have an extra sighter if a cease fire occurs and they keep the round in their barrel.

10.1.8 Interrupted Fire—If a range ceases fire during the firing of a relay
in individual matches at ranges of 500 yards or over, single or multiple stage,
one sighting shot will be allowed when fi ring again starts. If an individual
competitor is delayed over 2 consecutive minutes through no fault of his own
and is allowed additional fi ring time during the fi ring of an individual match
only at ranges of 500 yards or over, single or multiple stage, one sighting
shot will be allowed when his firing again starts.

Another forum had a report from a Black Hills' test of one lot of their 308 match ammo at 100 yards. Test groups started at about 1/4 inch average, 3/8 at 3000 rounds, 5/8 at 6000 and over 3/4 inch at 10,000. I cannot find it any more. Maybe Black Hills told their man to get it deleted.
.........
Regarding bore surface smooth issues, don't best barrel makers want a 10 to 15 microinch rough finish? Any bigger or smaller tends to copper foul too much.

 

[Bart B.]

If my barrel degraded 10% it would get tossed into the tomato patch or cut off some and rechambered.
The internet has all the answers.

Hornady told me their 308 Win test barrels' accuracy degrades that same rate as Sierra's and Black Hills'. How often have you shot the same load in rail gun barrels tracking group size trends across several hundred on them over thousands of rounds indoors with very consistent conditions and no human variables? It's OK to have different standards.

The Internet has some good answers. Some bad judgement and tests revealed, too.

 

[Mtstalker]

Shot it again today. 20 rounds. Looked like alot of copper in the barrel but after running a brush once there was almost none left. So at least its cleaning up alot faster. Yesterday at the end of 30 rounds there was very little copper. Nothing changed but on a good note i did find a load for it. But its only 2700fps with a 140, es 9 sd of 3. .200" groups