A twist on barrel break in question...... Bullet seating depth....

[J E Custom]

So. . . Would it be advisable to start a new barrel by scrubbing the chamber thoroughly with JB?

In My Opinion , NO

JB is an abrasive and you should not need anything like it on a custom barrel. the barrel maker has his own proprietary lapping procedure to get the best results for his barrels. The process may vary a little, and require more or less shots to reach the point where fouling is as good as it gets, and the introduction of anything abrasive is not needed or wanted.

The bullet does the best job of reaching this point and is the most consistent of all processes. If you break in a barrel correctly, you can tell/feel the barrel getting better by the resistance on the dry patch.
When it is done properly, you can feel the change for the better as you go. normally barrels reach this point between 7 and 15 rounds depending on the makers lapping process. cleaning between each shot is the only way to truly know when the barrel is ready.

Barrel Breakin is a slow and boring process, but the final outcome will depend on how well it is done, so don't rush it. Breakin also makes the load development process possible sooner and with less barrel wear(Shots) Accuracy occurs sooner also.

Once a person does a proper breakin and pays attention, he will be able to see/tell the difference Himself.

So my recommendation would be, never put anything through a custom barrel but a bullet.

J E CUSTOM

 

[WeiserBucks]

I agree 100% , a quality barrel doesn't need any abrasives. I think a lot of people degrade their perfectly good barrel by thinking some magic pixie dust is going to reinvent the wheel.

If pixie dust and snake oil was the answer, every barrel manufacturer would be using it .

 

[Rich Coyle]

I agree 100% , a quality barrel doesn't need any abrasives. I think a lot of people degrade their perfectly good barrel by thinking some magic pixie dust is going to reinvent the wheel.

If pixie dust and snake oil was the answer, every barrel manufacturer would be using it .

They want you to wear out the barrel.

 

[TwoMore]

I have only chambered a few dozen Barrels so I have to admit I think about the finish of the throat and how to make it less abrasive during break-in. specially with the longer leads and cuts with bore-riders that I have been doing lately. I have lightly smoothed up the throat with JB before. but have noticed that even those longer cut lands break in close to the same time as shorter throated barrels so I have just been doing the one shot and clean method. One thing I notice is when you are getting close to the end of the chambering process, going slow with plenty of cutting fluid and dont let the reamer load up with chips leaves a better finish

 

[Edd]

A couple years ago, I asked a prominent barrel mfg company owner, a name that everyone would recognize, about using Tubbs TMS bullets to smooth the reamer marks in the throat. He said...... "We advise against using them or any abrasive in our barrels because we have no control over what people will do to them but I fire lap all my personal barrels".

 

[Rich Coyle]

Edd,

I have fire lapped some of mine and even after they were broke in they became easier to clean and some became more accurate.

 

[HARPERC]

.....I have only chambered a few dozen Barrels..........

I think that is my issue, from the consumer standpoint, I haven't had enough new barrels to compare.
Some of what one hears is back and forth. I will say this thread has made me a little more positive about it.

 

[J E Custom]

I have only chambered a few dozen Barrels so I have to admit I think about the finish of the throat and how to make it less abrasive during break-in. specially with the longer leads and cuts with bore-riders that I have been doing lately. I have lightly smoothed up the throat with JB before. but have noticed that even those longer cut lands break in close to the same time as shorter throated barrels so I have just been doing the one shot and clean method. One thing I notice is when you are getting close to the end of the chambering process, going slow with plenty of cutting fluid and dont let the reamer load up with chips leaves a better finish

When I chamber a barrel. I first find out what spindle speed that Reamer likes best By trying different spindle speeds from 40 to 105 as the shoulder and body starts to cut. This tells me what speed the reamer cuts best at. then as I make cuts the reamer tells me when it starts to load up with chips and I reduce the feed depth to less feed depth as I go.

The deeper you go, the sooner the reamer loads up and constant reduction in depth of cut is necessary. Depending on the size and sharpness of the reamer, by the time I get within several hundred thousandths, I am down to .020 to .030 thousandths a cut and cleaning
the reamer and chamber between cuts. (A little slow, but worth the time.) normally the last few cuts are around .010 deep and a finish cut for head space is .005 + with a clean reamer and chamber.

This gives the total chamber including the throat, neck, and lead a very smooth finish that has no machine marks that need any special treatment.

I also use a high pressure grease on the reamer pilot to prevent it from marking the lands (It actually prevents metal to metal contact of the pilot and the lands, much like the oil in an engine prevents the crankshaft from touching the bearings ).

Most, if not all of the machine marks in a barrel are from the drilling operation. Premium barrels are first drilled, then reamed, and then laped to remove all of these marks/flaws. A well cut chamber will/should not add any defects to the part that is cut with a good reamer and a good chambering procedure.

I inspect all of my finished barrels with a borescope to verify its finish.
Although it is not the same as the lapped finish it has no machine marks and should not need any further processes other than breakin. The chamber should have a satin finish with no anular marks and needs no polishing if done right In My Opinion.

J E CUSTOM

 

[TwoMore]

When I chamber a barrel. I first find out what spindle speed that Reamer likes best By trying different spindle speeds from 40 to 105 as the shoulder and body starts to cut. This tells me what speed the reamer cuts best at. then as I make cuts the reamer tells me when it starts to load up with chips and I reduce the feed depth to less feed depth as I go.

The deeper you go, the sooner the reamer loads up and constant reduction in depth of cut is necessary. Depending on the size and sharpness of the reamer, by the time I get within several hundred thousandths, I am down to .020 to .030 thousandths a cut and cleaning
the reamer and chamber between cuts. (A little slow, but worth the time.) normally the last few cuts are around .010 deep and a finish cut for head space is .005 + with a clean reamer and chamber.

This gives the total chamber including the throat, neck, and lead a very smooth finish that has no machine marks that need any special treatment.

I also use a high pressure grease on the reamer pilot to prevent it from marking the lands (It actually prevents metal to metal contact of the pilot and the lands, much like the oil in an engine prevents the crankshaft from touching the bearings ).

Most, if not all of the machine marks in a barrel are from the drilling operation. Premium barrels are first drilled, then reamed, and then laped to remove all of these marks/flaws. A well cut chamber will/should not add any defects to the part that is cut with a good reamer and a good chambering procedure.

I inspect all of my finished barrels with a borescope to verify its finish.
Although it is not the same as the lapped finish it has no machine marks and should not need any further processes other than breakin. The chamber should have a satin finish with no anular marks and needs no polishing if done right In My Opinion.

J E CUSTOM

they way you are describing is the way I have basically gravitated to. but I have been using a 380 grit to give the main chamber body a sort of cross hatch just lightly. not polishing , it will be a satin finish. in my mind giving the brass a good surface to grip.

Thanx for you advice, I know I appreciate it for sure

 

[J E Custom]

they way you are describing is the way I have basically gravitated to. but I have been using a 380 grit to give the main chamber body a sort of cross hatch just lightly. not polishing , it will be a satin finish. in my mind giving the brass a good surface to grip.

Thanx for you advice, I know I appreciate it for sure

Thank you.
I gradually altered my procedure over time to this process because I got the best results for what I wanted. I started like many others and found ways to improve so I changed.

Getting in a hurry is not in my makeup and I consider it the number one enemy of quality. Without time restraints, I can take my time and
'try' for perfection. The old saying "If you can't find time to do it right the first time, where are you going to find time to fix it" says it all in my opinion.

There are other ways to get a good chamber, this is just the best way for me.

J E CUSTOM

 

[TwoMore]

Thank you.


Getting in a hurry is not in my makeup and I consider it the number one enemy of quality. Without time restraints, I can take my time and
'try' for perfection. The old saying "If you can't find time to do it right the first time, where are you going to find time to fix it" says it all in my opinion.



J E CUSTOM

that is so right!

 

[Edd]

I think a person should take the time to do it right but I also think the type of machine and tooling will have an affect on how long that is. I have read where one person says he can cut a perfect 308 size chamber in under 2 minutes.

 

[TwoMore]

I can do it in under 2 hours lol JK I started pre-boring and that helped my time.

 

[J E Custom]

I think a person should take the time to do it right but I also think the type of machine and tooling will have an affect on how long that is. I have read where one person says he can cut a perfect 308 size chamber in under 2 minutes.

WOW Thats scary ED
I guess with carbide reamers, oil pressure flush systems, And CNC machines anything is possible, But I for one would not want a 2 minute chamber. I have also heard people claim 20 minutes but again, That seems to fast for me. (I know that I take a long time)

Keeping everything clean, running the spindle to the optimum speed for the final finish inside the chamber and making sure everything remains true is more important to me than how fast I get done. I don't even think about when I will get through. I am done when I am done.

Chamber size, reamer quality and desired outcome have a lot to do with "How long". The fastest I can recall that a I ever Chambered a cartridge was a 17 HMR and that took 2 Hours. Big chambers have taken 6 to 8 hours. When I did lots of this type work I did not charge by the hour, I had a flat rate for all chambers. That way I had no time restraints and the finished chamber was the priority.

Everything seems to be time driven nowadays and quality is normally what suffers when cost goes down. Quality is Built In, not inspected in.

Just My Opinion

J E CUSTOM