Saturday, November 27, 2010

Metals used and a few vendor links

Due to a handful of questions and comments made by a few friends during a B.S. session the other day, I thought it might be useful to throw in some information about the material used to build not only the Bill Holmes .50 BMG rifle, but a number of other firearms.

Most of the material used on the .50 so far has been 4130 chromoly or 4140 chromoly. A decent write up on the properties of chromoly can be found here.

I guess it should be mentioned that I am NOT building this rifle, or any functional piece on it (aside from the buttstock and the bolt handle) from 1018 steel. Everything on this rifle is built from manufacture certified 4130 and 4140. This is not something I take lightly, given the unreal amount of pressure present in any rifle round, especially the .50 BMG.
This rifle, upon completion, will be taken to a professional for hardening. I would LOVE to have the capabilities to do this in my garage, but the reality is that this is one thing I feel better about taking to a professional. I have hardened steel parts before, such as extractors for AK's and smaller things of that nature, but a whole rifle is beyond my capabilities. I have no problems admitting that.

I have seen a handful of other homebuilt rifles finished and working that were based on the same basic design I am using.Were I purely starting from scratch and designing everything myself, then this might well be a dangerous proposition. I see no reason why anyone with a handful of tools and access to a mill and a lathe and appropriate materials could not build this rifle or any like it.

With all that said, I have a policy of giving credit where credit is due.  From that, I should throw in my personal recommendations to the following metal suppliers, all of whom deal in small quantities of just about any kind of material you could think of.

1. Aircraft Spruce and Specialty. I highly recommend this company, as the price was right, the shipping was fast, and the service was great. I bought the 4130 tubing for my receiver from there. I'm no shill, just a happy customer

2. Online Metals Great service, prices were a little steep on a few things. Decent shipping rates. Again, I'm no shill, just happy enough as a customer that I have no problem recommending them to others. Metals can be purchased by the foot and by the inch.

3. Speedy Metals Pretty much the same as Online Metals, although prices are a bit lower at Speedy Metals. Great service, fast shipping, etc. They gifted me with nothing except a good experience.

Pretty much any metal stock needed for anything I can think of can be acquired from one or more of these three suppliers.

So far, without the price of the barrel, I have about 125 bucks invested in the rifle through the metal I have purchased through these suppliers. If I recall, I paid about 225 for my M3 barrel, so I should have less than 400 bucks in the rifle by the time I am done, prior to purchasing optics. Of course, that does not cover lathe cutting bits, drill bits, welding gas, grinding wheels, end mills, and a few other odds and ends (firing pin springs, fire control group parts, etc). So, I guess I'll be out close to 500 bucks before optics.

For what it's worth, I plan to do another update in the next day or so over more of the build, and I may actually toss up a pic of the assembled rifle if I can get some batteries for my camera. Most of the work on the rifle has already been done and most of what I have posted up is actually stuff I did a couple of months ago.

Stay tuned.........

Wednesday, November 24, 2010

More machining on the bolt......

Okay, so I had already turned down the outer end on the bolt in anticipation of machining the locking lugs on the bolt. The original Holmes design calls for machining 3 male lugs on the bolt. I have seen a few designs, such as the serbu BFG.50 that use only two lugs. There doesn't seem to be a whole lot of difference between the two, at least not when it comes to functionality. So, I went into my CAD system and sketched out the lug system, printed it out and glued it to the bolt face. From there I took a punch and outlined all the areas that needed to be milled out.
I had an old lathe headstock laying around that was still functional but had been replaced due to age. I made a set of mounts for the lathe headstock that would allow me to bolt it to the milling table. The headstock of the lathe had a locking stud and with that locking stud there are indicator holes every 6 degrees. I set the bolt up in the chuck on the old lathe headstock and used that as a dividing head of sorts. From there I just supported the opposite end of the bolt directly below the area being machined and then went to milling it out alternating between a 1/2" cobalt end mill and a 1/4" carbide end mill.




No, the wood is not what's supporting the bolt in those pics. There's actually a set of machined steel blocks under the bolt supporting it.

After a couple hours of cussing and milling, rotating and milling, and a whole lot more cussing, I had a more-or-less machined bolt. I wasn't real happy with the finish the end mills left (the cobalt one was getting dull and the carbide one was chipped pretty badly.), so I made sure and left about .01 inch of material on the area being machined so that I could fine tune the bolt with a file and some sandpaper. That was an exercise in insanity all by itself.



For those who are looking closely, you can tell this was indeed built in my garage, as you can see my weedeater in the background of one of the pics.

And.......after a short trip back to the lathe to take a couple thou off the outside of the bolt, this is what it looks like so far...
More on the bolt later. For now, it's on to the chamber and the actual tube receiver.....

Blog has been updated a bit

Finally made some additions and changes as well as an update has been added.
More updates to come.....

Machining the bolt on the .50

I suppose an update is in order.
I had been working a steady schedule with my employer right up until the middle of September, wherein I had to work a normal "banker's hours" schedule. Between work and college classes, I would oftentimes get home from work/class too tired to work on any of my side projects, let alone blog about it. Now I am back on my normal schedule and actually have time to do my normal thing, which includes tinkering in the garage.

So, as of my last update, I had machined the tapered barrel guide, turned the barrel down to the diameter I wanted and threaded it for a muzzle brake and a barrel retaining nut. 4140 is pretty good stuff when it comes to machining, which is good because by the time I got done machining the barrel, barrel nut, and tapered barrel guide I had a HUGE pile of chips and curls left over. Next up was machining the bolt.

I started out with a 2" piece of 4140 solid round stock about 9 inches long, chucked it up in the lathe between a live center with a steady rest supporting the bolt material as well. I started to machine the area that would contain the chamber lugs by turning the last 1.75 inches of the bolt down to a 1.5" outer diameter.




I then measured an inch back and machined that 3/4 inch long section down to a 1 inch outer diameter.


Next up, I needed to machine the lugs on the bolt so that when a round is chambered and fired, the rifle doesn't blow apart. This needed to be machined on the milling machine. Despite my best efforts, I had to do some final finishing work with a file and some sandpaper. :\
More on this in a bit.....

Welcome Saysuncle readers

Holy crap!!
An Unclelanche!

Haven't updated in a few weeks because of work wearing me pretty thin. Guess I will have to update now, since the rifle is almost done.

There's not a whole lot of WECSOG to be seen here, at any rate.