You probably already owned the right tool for the job and didn't know it, the M10, aka your sectional cleaning rod handle. Here's a good writeup
http://www.cobs.com/lprgc/garandb.htm
M1 Garand Bolt Disassembly and Reassembly:
Disassembly:
The Garand bolt (and I suspect the m14) can be disassembled using the Combination tool, M10 (also known as the cleaning rod handle!). You need the real deal with the 1/8" thick 'blade' in one end. Insert the SMOOTH end of the M10 (the screwdriver end; it will shoulder on the waist so it will not scratch the chamber) into the chamber, and insert a section of cleaning rod into the unthreaded hole on the M10.
Engage the blade below the lip of the extractor and GENTLY twist the M10 receiver-up using the handle. The extractor should come loose in a controlled manner. Decreasing tension on the op rod handle will let the pieces fall loose.
Reassembly:
To reassemble, install the extractor plunger and spring, and the ejector and spring, and close tightly on the previously installed M10 (holding the tongue just "so"). While pressing the bolt in the closed direction, drop the extractor into its boss, and tap home. VOILA!
I learned this at a CMP shoot. (Help, my bolt disassembled itself!)- a few of Walt's parts (NEW springs, et al) and I was on my way!
My 'old' bolt disassembled itself, so I had a new parts (springs, extractor, plungers) in my tool kit. A CMP shooter (member of Palmetto State Marksman's Association) from North Augusta SC did the trick. I wish I could find his name. When I do, I'll forward it for credit, too!
NOTE: the SMOOTH end of the M10 is actually the end that looks like a screwdriver. The notched end has the BLADE that sticks out from the side.
Information Provided by E.M. Dannemiller II (emdannemillerii@mindspring.com), used with permission.
You can also use the M3A1 tool for the same purpose. Place the chamber brush in the chamber, the back end of the brush acts the same way the M10 back end does. And you don't even have to use a cleaning rod section.