Reamers are precision ground chamber cutters perfectly sized and contoured for a firearm’s cartridge. Reamers are critical to cutting the barrel for accuracy and function. Pistol barrels are primarily straight-walled, making cutting chambers either by hand or machine somewhat easy. Pistol reamers are important for accuracy and function. Too short a chamber and the pistol or revolver might not cycle. Too long and you can get excessive leading and accuracy loss.
I buy my barrels with short “gunsmith” chambers, allowing for finish reaming after the barrel has been installed. In most cases a “chamber reamer” can be used to cleanly cut the remaining five to 10 thousandths for proper headspace. But the chamber reamer doesn’t always cut the “throat” which is the transition area from smooth chamber wall to the barrel rifling (lands and grooves). A barrel throat should be angled at about two degrees, and, by using two reamers, the chamber or roughing reamer, and the throat or finish reamer, you will save tool life and get better cuts. If you’re using a semi-fit barrel, the finish reamer can do all the work for the occasional barrel fit.
Demystified: Chamber Reamers
Reamers are used to rough or “finish” cut chambers. The two “Go-No-Go” gauges (left) are
used to check your work. Clymer, Pacific Tool and Gauge and Dave Manson make the reamers.
The 1911 barrel-link cutting jig from Powder River Precision makes cutting custom barrel links a whole lot easier.
Man Vs. Machine
Hand cutting requires an adjustable tap wrench to hold the reamer. Also needed is a Go- No-Go gauge for the caliber barrel you’re fitting. The reamer is placed in the short-chambered barrel secured in a vise vertically. The reamer is slowly turned in a clockwise direction while being lubricated with cutting fluid like Kroil. A finish pistol reamer for a .45 or 9mm cartridge — seating off the case mouth — should be cut to a depth allowing the case gauge to sit flush with the barrel hood. If you don’t have a gauge, a quality factory loaded round can be used to gauge the chamber length.
Some reamers allow for a stop collar, preventing over-cutting the chamber. This could prevent the firing pin from reaching the primer. So go slowly and check your depth often. Let gravity do the work, very little down pressure is needed.
A more precise method for chambering is using the lathe. The barrel is mounted in a collet or lathe chuck via the headstock. The reamer is mounted in the tailstock using a floating reamer holder. The holder allows the reamer to cut true, following the barrel bore even with a slight misalignment between the headstock and tailstock.
These reamers have a “live” or spinning pilot, preventing damage to the rifling while turning in the lathe. I use the slowest rpm on my lathe with plenty of flood lubrication. As the barrel turns the stationary reamer is moved into the chamber with the tailstock a few thousands of a time. The reamer is backed out and the chamber measured with a “Go-Gauge” until the proper fit is achieved.
Pacific Tool and Gauge owner David Kiff went into great detail about how each “flute” or cutting blade had a slightly different design for cleaner cuts and smoother finish. David has been designing and manufacturing reamers since 1977. PTG as well as Clymer and Manson reamers are all used in my shop and each maker offers custom cutters for the gunsmith trade.
Link Fixer
I also recently found a great new jig for cutting 1911-barrel links. Designed by Dan Bachelor of Powder River Precision it allows me to cut barrel links in the length I want instead of trying to modify an off-the-shelf link. The jig is supplied with uncut link “blanks” for the slide stop pin. It has a gauge pin to zero from with a coaxial indicator. Move 1″ to center over the link pinhole, then adjust to mill the slide stop pin hole. I drill with a 13/64″ cutter, and ream to 0.204″. This is great for precision fits where the pre-made numeric links won’t fit — no more oval holes cut with a file. He also has a prototype unit in the works with each hole size indexed in thousandths.
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