It is not often that most people think how something was done in the “Old Days” but I do. Lots of times you can not reproduce a part using modern machinery with a great deal of work. The “Old Days” I am talking about is not the 1600,1700, 1800, but the middle 1900’s. I just received some real interesting pictures on making the AR-18 bolt carrier. Did you ever thing how they made the bolt cam track on an early AR-18. This is the days before cnc machining. This is the tool used to make the cam in the bolt carrier for the first prototype rifles.
Sorry for the quality of the pictures, it is how they cam. If anyone knows the were about of this tool please contact me. I would like to take better pictures.
An interesting article! Too bad the quality of the pix wasn’t better. I thought about this for a while and then I decided that the camtrack cutting on the AR18’s bolt carrier was the most complicated machining op on the entire rifle. Same goes for the M1, M1 Carbine and M14. Of course nowadays we have CNC machines to cut these camtracks and rotate the bolt carrier as the op is done! So in the good old days they needed a dedicated machine to do this machining. The actual camtrack is a helix making it more difficult to fabricate. A straight mill cut will work but a helix is the best way to go.
The skill of the tool and die makers that built these guns is awe inspiring.
I could only hope to learn those skills someday.
Rick@AR180S.com
Rick, I could not agree with you more concerning the skill of these “old craftsman”. Many years back I went to Trinidad State Junior College for some NRA gunsmithing classes. One of the faculty, Leonard Bull, was trained in England in the old apprentice system. The man was an expert with a hand file. He told the story of how one of the final exercises the apprentice had to master solely with hand tools was to take a slab of half inch steel, bore a hole one inch square, and fit a one inch square block into that hole with tolerances so close that the block would slip through the hole slowly but not fall through. He was always encouraging student to use hand tools rather than the mill and other power tools.
I remember one student who was hardheaded would argue that this is the age of machines, not hand tools. One day this student ask Leonard something about setting up the mill to make a part. Leonard simply said, “do it with a file”. The student laughed at him with the remark, “that would take all day”. Leonard challenged him to a race, Leonard would do it with a hand file and the student would do it on the mill. The prize was a case of English Beer. On the start of “Go” the student took off for the supply room to gather the raw material and the tools needed for setup on the mill while Leonard got a hand file and a piece of appropriate material out of the scrap box and started working. Leonard, of course, won. The student had not counted the amount of time it took to gather tools for setup, doing the setup, making adjustments, etc. We didn’t hear a whole lot of bragging from that student after that.
This appears a bit like a stock copying mill?
I suspect that the Cam Tracker is following a similar and maybe even “positive” model of the cam-way, thereby cutting with a tool head the exact repeatable cam-way each time? I would certainly not expect that the cam-way had variables each time the bolt carrier was placed in the “carriage”.
The operation that boggles my mind is how the internal helical cams were cut on the inside of an 1895 Mannlicher straight-pull rifle bolt carrier. They’re long, tall, helical ‘lands’ like the lands of a rifle barrel, but the bolt carrier is not entirely open-ended. It’s been quite a few years since I looked at mine but I remember coming to the conclusion that it couldn’t be cut quite the same way as a barrel is rifled – there’s a lot more metal to be removed, and I think the cams go all the way to the blind end of the carrier. This was also plainly not a welded-on end (too early technologically).
One of my experienced machinist friends said he could conceive of how to do it, but while he’s normally good at describing machining operations, his description didn’t make much sense to me and he admitted it was a really complex operation.