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

[KyCarl]

Couldn't you rough out the chamber with a boring bar and leave about .015
to take out with the reamer? Small light cuts rather than hogging full diameter?
High pressure oil from the other end forcing the chips to the rear.
Watch your readout and go in 2 or 3 thousandths burp it Repeat till to depth?
Should leave a great finish...

 

[J E Custom]

Couldn't you rough out the chamber with a boring bar and leave about .015
to take out with the reamer? Small light cuts rather than hogging full diameter?
High pressure oil from the other end forcing the chips to the rear.
Watch your readout and go in 2 or 3 thousandths burp it Repeat till to depth?
Should leave a great finish...

When I first started chambering I tried roughing reamers, drilling, boring and many other techniques but the outcome was always less than desirable. (For me) after being trained by a benchrest shooter and Smith and seeing the end results.

He tried to tell me there were no shortcuts when it came to a perfect chamber. I finally got the message and started doing it the way he told me to and the procedure has changed very little over the years.

There are many ways to speed up the process, But slow and steady is
the best In My Opinion. It takes years for a gunsmith to perfect the way he chambers to get the results he wants, and even though the procedure may be different, it works for him.

The plus side to the way I was taught is that reamers stay sharp and seem to last forever. Many of my first reamers have cut dozens of chambers and still don't need sharpening and cut beautiful chambers.

J E CUSTOM

 

[Edd]

This discussion made me curious enough to attempt to add something to my knowledge.

On the JGS website there is a recommendation on reamer speeds and feed rates. I'd guess there are many other places that have this information listed but this is the first place I found it.

Here is the math showing the slowest and fastest recommended.

HSS reamer at 150 RPM's and a .004" per rotation feed is the slowest. Carbide reamer at 400 RPM's and a .006" per rotation is the fastest. They do have some things listed that would cause exceptions.

A 308 Winchester chamber is 2.025" deep.

Based on this, the slowest time for cutting a chamber would be 3-3/8 minutes and the fastest time would be 50-5/8 seconds.

 

[J E Custom]

This discussion made me curious enough to attempt to add something to my knowledge.

On the JGS website there is a recommendation on reamer speeds and feed rates. I'd guess there are many other places that have this information listed but this is the first place I found it.

Here is the math showing the slowest and fastest recommended.

HSS reamer at 150 RPM's and a .004" per rotation feed is the slowest. Carbide reamer at 400 RPM's and a .006" per rotation is the fastest. They do have some things listed that would cause exceptions.

A 308 Winchester chamber is 2.025" deep.

Based on this, the slowest time for cutting a chamber would be 3-3/8 minutes and the fastest time would be 50-5/8 seconds.

No argument hear, Just for discussion

That's a good description of the time to cut a chamber if you did not stop and clean or just to inspect. Some reamer makers say you can run their reamers @ 250+ RPM and Carbide likes faster spindle speeds for all cutting So I believe 400 rpm +.

I don't have/use a high pressure cutting oil system (I tried one) because It made such a mess and the fact that I am anal, I have to stop often and look at the chamber to check the cut quality. I realize that they work, but I just prefer stopping and cleaning often. I also feel what the reamer is doing and know when to stop feeding if anything is wrong.

I know smiths that use oil systems and do great chambers, I just didn't need the speed or the trouble if something goes wrong. I stop and check just to make sure something has not gone wrong and I still have time to correct anything i don't like before the chamber is finished . If anything does go wrong, using a flush system it may cause problems
that can't be fixed without setting the shoulder back and spending more time fixing it.

Again I would never tell a smith how to chamber, he does what he wants hopefully because it produces the best results for him and his equipment.

My way works for me and is very dependable/consistent chamber to chamber using my equipment.

J E CUSTOM

 

[J E Custom]

The fact that I inspect all of my barrels during, and after final chambering puts me at a disadvantage as to the throat and lead area of the chamber needing to be fire lapped because I see no signs of annular rings in this area. there are sharp edges that will foul at first but they seem to break in at close to the same rate as the barrel, and buy the time the brake in is complete, this area looks as good as the rest of the bore.

I believe that fire lapping "Can" be good in certain applications to help remove any marks left by the reamer, But only in the hands of someone that knows what they are looking at and has a borescope to see the progress as they are doing it. Otherwise, they may do more damage than good.

The fact that it is an abrasive process, My instincts are that It can reduce barrel life and is best left to those barrels that are rough and need some help improving there accuracy, if only for a little less time.

There are other process that sound like the answer to all problems like fire lapping, but if not needed or the problem could be something else
they could do more damage than good. So they should not be part of a general procedure and should only be used if it is the only way to solve a problem.

Just like lapping a barrel, should only be done as a last resort and by someone that has the proper tools and experience to do it correctly, and inspect it to reach the best results.

Just my opinion

J E CUSTOM