Chamber reaming/finishing


November 17, 2006, 01:01 PM
I have read about the need for it, but never the procedure nor tools involved. So how is it done? Let's say I have a 1911 barrel at home that might come undersized from the factory. What gauges and tools would I need to finish the chamber?

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November 17, 2006, 02:56 PM
A headspace gauge set and a hand-turned finishing reamer with a pilot will do for light cleanup in a tapered or slightly undersized chamber. Figure on about a hundred bucks or so for the tools. For heavier work or a badly out-of-spec chamber, you'll need a lathe.

Gun Plumber
November 17, 2006, 03:01 PM
OK, first, if you DID get any new weapon that has excessive headspace, send that sucker back.

If it's an older weapon of yours or one you purchased used, just go out and purchase a new barrel.

MOST chamber work I've done is done on rifles, generally centerfire rifles.

The steps are this (this is SEVERELY shortened)

Chuck up the barrel in the lathe.
Put the appropriate reamer on the steady (non-turning) end of the lathe.
Start the barrel turning (slowly) and bring the reamer into contact with the barrel.
After removing a certain amount (you should KNOW this measurement BEFORE starting this procedure) and it IS different with each headspace job.
Once you have turned down the chamber, mount the barrel to the receiver and put the bolt in place WITH the correct headspace gauge (don't forget that when you finally mount the barrel to the reciever you will have about two to three thousands of 'crush' - tightening down the barrel to the receiver).

Continue this procedure until you have correct headspace. Pull the barrel/receiver from lathe. Tighten down to include the crush. IF you made a mistake, remove the barrel from the receiver, put back in lathe. IF you cut the chamber too shallow, just continue cutting. IF you cut the chamber too deep, you will have to cut the end of the threading short, rethread it, then start over again.

LIKE I SAID, I shortened the procedure a lot. Like making sure the barrel is centered. Like properly mounting the chamber reamer. Like how to properly insert the chamber reamer into the chamber. LOADS OF THINGS.

Using a chamber reamer are NOT for the faint of heart. You will not only need to know HOW to use a lathe. You will also need to know how to mount and remove a barrel from the receiver. Thre so much to know, it's really something that is best left to a professional.

One mistake can cause catastrophic failure of the KABOOM kind.

So I hope that helps.

Jim K
November 17, 2006, 03:27 PM
If you get a 1911 barrel that has the wrong headspace, send it back. They should be "drop in".

For bolt rifles, I used the lathe only with the rougher and the very first passes with the finisher. If the barrel was short chambered (as many new ones are) I would just install it, then use the finisher manually to get the right headspace. Today, that whole business can be skipped and once the barrel is ready for a finish reamer it can be installed and a pull through reamer used instead of all that trial and error.


November 17, 2006, 03:53 PM
Just curious. Thank you for the replies. I am mainly interested in the final finish type reaming that 1911Tuner describes. I don't have any guns that don't run due to a tight chamber I was just interested in the process. I was looking at the reamer in Brownells
Doesn't look like it can be used by hand, what is a pilot? How does it work?

November 17, 2006, 05:16 PM
You can do it with a hand reamer if all you need to do is clean up the chamber. I have a lathe, so I chuck the barrel loosely, and slip in the reamer that is chucked in a good tap handle that's been center drilled. Slip a dead center into the tailstock and bring it forward...tightening the lathe chuck as I go. When it's all chucked up, I add a tiny bit of pressure to the tap handle and lock the tailstock...turn the reamer twice, and back off the pressure.
Turn the reamer clockwise as you draw it out. Never turn a reamer backward, and use plenty of good cutting oil. Tap magic will work. Personally, I like the smell of Kool Tool, but I don't even think it's available any more.

If you need to make the chamber deeper by a few thousandths, turn the reamer and advance it by cranking on the tailstock handwheel, if so equipped.
It should have a scale on it to let you read the amount of advance. Use the
"Rule of Halves" and cut half as much as you think you need to, and re-check with the GO gauge. For heavier work, you really need to chuck the reamer into the tailstock. For precise work, use a 4-jaw independent chuck and a dial indicator.

Gun Plumber...Cutting the chamber shoulder deeper won't create excessive headspace in the kaboom direction. Only in the "Wonder why I'm gettin' so many misfires" direction.

Jim Watson
November 17, 2006, 06:04 PM
A substantial number of .45s these days are coming through with undersize chambers. I think the high priced spread is doing it to advertise "minimum match chambers" and machine rest groups a fraction smaller at the expense of reliability. I think the cheap guns' makers are trying to get too many barrels out of a worn reamer. Same result, a lot of them need a sharp reamer run in all the way before you can count on them.

Easier to seek out a reputable gunsmith than to enrich Fed-up sending guns back for the warranty clerk to try to figure out.

November 17, 2006, 06:30 PM
Jim Watson wrote:

>A substantial number of .45s these days are coming through with undersize chambers. A lot of them need a sharp reamer run in all the way before you can count on them.<


+1, Jim...and a good many are tapered about a 16th inch or so behind the shoulder, which leads me to suspect that they may be trying to get by with multiple tool resharpenings...well past the point that they should be replaced.
Everybody's tryin' to cut corners these days...and the buying public draws the short straw way too often.

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