Lapping throat of custom barrel

[J E Custom]

Lapping a barrel after it is chambered Is a bad idea.
Custom barrels are lapped as a blank and based on the barrel ID the muzzle is determined from the manufacture.

Because Lapping takes more material at each end of the bore when the lap is reversed, some barrel makers make a saw cut in the muzzle end about 1/2 to 3/4' From the end to force the builder to remove this area.
The chamber reamer removes this area and more so nothing has to be done to the chamber end of the barrel.

The usable bore is left remaining in a lapped state if the barreling process is done right. I always recommend ordering a barrel blank 2" longer that the finished length to remove enough to reach true bore diameters. Most barrels can be 1" longer and still be ok, but 2'' just assures that any taper that may have been induced by the lapping process is removed. Many barrel makers don't charge you for this 2"
overage.

So I absolutely don't recommend any polishing or lapping after the chamber is cut. The bullet will take any sharp edges off if they are present. Any polishing or lapping of a finished chamber will only diminish accurate dimensions produced by the reamer, and potential accuracy.

J E CUSTOM

 

[TwoMore]

I absolutely respect your knowledge! and love to read your thoughts ,but cleaning the throat from any burr's before firing I just cant see the problem,I am a perfectly experienced precision machinist , when I messed up and rented a dull throater and could see the burr's i was just unwilling to fire that down a 800 dollar proof barrel. It took very little effort to get it to where I felt the firing a bullet would not take those burrs down the bore. It all turned out good with the rifle as it is shoots well under .5. I did not lap the barrel just cleaned the throat. Now 99 percent of the chambers I use custom reamers but this was one of the first,where the customer provided the reamer and the ammo he wanted to use I had to throat deeper it was my mistake. There are going to be instances where some work will have to be done IMHO have a great weekend

 

[shortgrass]

That's why I own my throating reamers! Everybody and their dog is renting reamers to "do their own barrel work". IMO, the companies that rent out reamers does a poor job of inspecting for sharpness when the rented reamer(s) come back. I'll trust my own tools, thank you. I seem to always suspect customer supplied tooling, also. I always take a barrel stub and cut to the shoulder, just so I can get a 'feel' for the tool and examine throat length for myself.

 

[TwoMore]

That's why I own my throating reamers! Everybody and their dog is renting reamers to "do their own barrel work". IMO, the companies that rent out reamers does a poor job of inspecting for sharpness when the rented reamer(s) come back. I'll trust my own tools, thank you. I seem to always suspect customer supplied tooling, also. I always take a barrel stub and cut to the shoulder, just so I can get a 'feel' for the tool and examine throat length for myself.

Thank you! I now have to agree 100 % its a big investment

 

[TwoMore]

There is no telling how many barrels are sent down the way by insufficient reamers and machinist that dont even bother or dont have the means to look

 

[TwoMore]

That's why I own my throating reamers! Everybody and their dog is renting reamers to "do their own barrel work". IMO, the companies that rent out reamers does a poor job of inspecting for sharpness when the rented reamer(s) come back. I'll trust my own tools, thank you. I seem to always suspect customer supplied tooling, also. I always take a barrel stub and cut to the shoulder, just so I can get a 'feel' for the tool and examine throat length for myself.

by the way I follow your post too , this is a very good site

 

[J E Custom]

I absolutely respect your knowledge! and love to read your thoughts ,but cleaning the throat from any burr's before firing I just cant see the problem,I am a perfectly experienced precision machinist , when I messed up and rented a dull throater and could see the burr's i was just unwilling to fire that down a 800 dollar proof barrel. It took very little effort to get it to where I felt the firing a bullet would not take those burrs down the bore. It all turned out good with the rifle as it is shoots well under .5. I did not lap the barrel just cleaned the throat. Now 99 percent of the chambers I use custom reamers but this was one of the first,where the customer provided the reamer and the ammo he wanted to use I had to throat deeper it was my mistake. There are going to be instances where some work will have to be done IMHO have a great weekend

You learned the hard way about how a poor/dull reamer does and I am sorry. The reason I post many times is to prevent this type of thing from happening. In my shop, reamers are treated like diamonds. they all have protected sleeves and separate bins for storage. so they never touch each other. I am also very picky about the manufacture and currently only buy two brands because of the way they cut. I can't blame you for cleaning up the throat if it was bad, but the reason I said that a rough throat was a sign of something wrong was the purpose.

Just like the polishing of a chamber means that the reamer was not sharp and/or the spindle speed was wrong. And your experiences were nothing that most smiths haven't experienced. I do a lot of repair to rifles that have great barrels but poor craftsmanship. there was also mention of solid pilot marks earlier and this can be remedied
if you under stand the cause, and how to prevent it.

I have both solid piloted and removable piloted reamers and find that the solid pilots work very good as long as they fit properly. I have a 3 set removable pilot set for each piloted reamer because some barrels are different than others and the fit is critical. the solid pilot reamers must fit, and if I don't like the fit I will normally replace it with a removable piloted reamer. On these reamers I also always use a heavy high temp/pressure grease to prevent it from leaving any marks and to improve the fit.

There are so many things that can go wrong, that If you know the sign, sometimes you can overcome them.

J E CUSTOM

 

[swd]

The biggest question is does the gunsmith actually know what he's doing when it comes to lapping a throat. I'd say a lot more guys don't know than do. Personally I would never let anyone touch the inside of a barrel it was chambered by a competent gunsmith.