Professional Damage’s Chambering System
Figure 1: img
Overview
As part of the barrel manufacturing process a chamber must be machined in the
barrel. This is where the cartridge will be placed into and fired from.
The chamber diameter and geometry differs per cartridge. These specifications
are taken from SAAMI.
SAAMI Chamber Drawings
For example, the .22LR cartridge needs a chamber diameter of 5.77mm (.217“).
A great way to achieve this is with Electro Chemical Machining (ECM). At this
time only straight walled cartridge chambers can be ECMed.
This document will outline the basic steps to chamber out a pipe to a desired
diameter using this technique. ## Process
Referring to the diagram for below explanation.
To increase the inside bore diameter of the barrel, electrolyte solution is ran
through the boring fixtures (1 & 2) using a high pressure pump.
A current is run between the barrel (3) and the rod (4) that runs down the
centre.
O-rings in the fixtures stop the high pressure electrolyte from leaking. Clamps
(8) ensure the fixtures do not blow off during operation.
1
Figure 2: img.png
2
Figure 3: img_2.png
Required materials
The following are a minimum requirement to perform this operation.
Specific materials:
• 1x boring fixture
• 1x boring rod to match
• 1x barrel
• 1x O-ring to match barrel diameter
• 1x O-ring to match rod diameter
• 1x 25mm worm drive hose clamps
• Gauge pin (to match chamber diameter)
Basic materials:
Material list
Warnings
See warnings
Preparation
Using brake cleaner, acetone or similar solvent to make spotless the inside of
the barrel. This will require forcing solvent soaked pieces of rag down the barrel
several times to remove all impurities.
Anything that can insulate electrical current will affect the cut of the barrel.
CLEARLY MARK THE CHAMBERED SIDE OF THE BARREL.
3
Method
Read the following first: This method uses the same parts as the boring. However,
only one boring fixture is used.
Using the back of a vernier caliper measure the amount of rod poking out by
touching the rod to the back of the vernier caliper and the mating face where
the barrel touches the fixture. See images below for reference.
Figure 4: img_4.png
The image shows 22mm which is the required chamber depth for 22LR.
Once the rod is poking out to the correct depth, tighten M3 bolts in rear to
secure the rod, so it doesn’t move during cutting operations.
The chamber cutting process happens very quickly. I recommend no more than
1 minute cuts.
Checking is easier than starting again.
ENSURE CHAMBERING FIXTURE IS PUSHED COMPLETELY FLUSH
AGAINST THE BARREL FACE.
Then follow the general instructions:
General ECM steps
4
Figure 5: img_5.png
5
Notes
You can use unfired cartridges or a gauge pin or a vernier caliper for the
measurements. I suggest using all 3.
// TODO clarify this issue I have been using a chamber rod without a insulator
at the end to cut the chamber as well as cut the throat.
The throat is cut simultaneously with the chamber ( a radius appears near the
chamber and beginning of the landings)
