Saturday, February 26, 2011


Being sick sucks.
Don't know if this is the flu or just a real nasty cold but it really has knocked me on my can.
Blogging light for a bit.

Wednesday, February 23, 2011

Suomi M31 update

Well, the metal for the .50 BMG still has not arrived, so I did a little more work on the M31.

As previously mentioned, I have to do this work in a certain order to prevent becoming a felon. I certainly don't want to blog about something and toss up pics that would later lead to my conviction, should I have a brain fart and forget to do something by the book. With that in mind, I had to modify the barrel first and make sure it was legal length before I made a modified receiver extension that the barrel mounts to. Had I made the receiver extension first, I would have then had to modify the barrel to fit this extension, and by the definition of the ignorant stupid asinine ridiculous law, I would have then broken the law in terms of constructive possession, as I would have had the components on hand to assemble a short-barreled rifle. So, the barrel gets modified and lengthened first, then the receiver extension gets made. And when the receiver extension is made, at no point is it capable of accepting a factory short barrel.

Am I being paranoid? Probably. But, being paranoid and cautious usually keeps one from being a guest of the state in a concrete room.

With that said, I figured the easiest way to make the receiver extension assembly unable to ever take a factory 12" barrel would be to turn down the end of my barrel and thread it, then thread the receiver extension to accept the barrel. This would be turned to 3/4"x16 t.p.i.
Here I chucked up the barrel and started to turn down the chamber end down to .75" OD from its original  diameter of .8"

 Next, I just happened to have a 3/4"x 16 tpi tap, so I figured that was good enough. So, I set the lathe to 16 threads per inch and cut the threads about .04" deep.
 Next, I had to make sure the barrel was at least 16" long, so I turned down the last 1 1/2" of the barrel to 5/8" OD, being very careful not to bung up the crowning.

With the barrel threaded on the chamber end and turned down on the muzzle end, I took a quick picture or two.

  Next, since the factory barrel is 12" long, and I was going to slip a piece of steel over the barrel and silver solder it in to make it legal length, I turned down a 5 1/2" piece of 1" diameter hot roll steel to 3/4" OD and bored it out to 1/2" all the way through and then bored it out to 5/8" ID on one end about 1.5" deep. This would allow it to slip over the factory barrel and act as an acceptable barrel extension, according to the ATF.

The whole assembly is yet to be silver soldered together, but that will probably happen tomorrow. More pics then, perhaps in a couple days.

Monday, February 21, 2011

Another project undertaken (very picture heavy)

For those of you who have been wondering about other projects I have in the works, here's a post for you.
I've taken a couple days off of working on the .50, mainly because I'm waiting for some steel to arrive with which I will work on the bipod and buttstock area.

A while back I procured a couple of Suomi m31 parts kits from a friend, one of which was 100% complete and the other was......not. I have enough parts to build two, but one of them is not going to have all the original stuff. I am saving it for later. First, I wanted to build one that would mimic the original M31. For those of you who are unaware of what an M31 is, go here.
I'm not too fond of the aesthetics of these guns, but the parts kits are cheap, and when it comes down to it, it's hard to argue with a 9mm carbine that holds 72 rounds of ammo in a drum. The biggest problem is, the doggone rifle is heavy. However, the parts kits are still available for around 100 dollars, and are fairly easy to machine the working parts for. One setback I've encountered is that it is originally an open-bolt submachine gun, and in order to be legal, none of the original full auto components can be used in their original configurations. This means converting the rifle to closed-bolt operation, which is a pain compared to the open bolt arrangement. I do not exaggerate when I say that a functional sub machine gun could be built in a matter of hours versus a semi-auto taking a handful of days. This is, of course, if you already have all the springs, magazine, bolt, and small parts.

To start, the receiver of this rifle has been cut to BATFE specs, which nowadays means it was torched apart into three different pieces. This pretty much leaves you with a pile of slag and unidentifiable metal scrap. I had to do a lot of research on this rifle in order to get some measurements that I could transfer to a new receiver. The new receiver could not be capable of accepting the original bolt, so after I took a bunch of measurements, I ordered some 4130 tubing that had close to the same outer dimension but a smaller inner dimension. This will allow me to turn the old bolt down on a lathe to fit snugly in the new receiver, but a standard bolt would not fit. The original bolt will also be highly modified so that it no longer works in an open bolt configuration.

I took some measurements and found that the receiver was 1.46" outer diameter and roughly 1.16" inner diameter. Since the magazine well components would have to be salvaged from what remained of the old receiver, I had to come pretty close to that outer dimension for the old mag well parts to fit snugly on the new receiver. There is also a section inside the original receiver that is about .75" inner diameter where the end of the bolt travels, right above the mag well. I was not about to bore out a 12" long piece of solid stock to two different inner dimensions. Luckily, I was able to purchase some 1.5" OD 4130 tubing from Aircraft Spuce and Specialty pretty cheaply. I ordered it with a 1.105" inner diameter, so that a factory bolt would not fit. I also ordered a piece of 1.5" solid round stock that I could machine to fit inside the receiver and weld in place that would take the place of the original .75" inner diameter section. This section includes the lugs that allow the quick-change barrel to be mounted. More on that later.

Here's the original kit and receiver in all it's......uh.....glory.

The new receiver tubing

 And, the old receiver

Some pics of the kit when "assembled"

 Now, I've sat on this project for a while, and finally this last weekend decided to get down to brass tacks and start on it. I began by taking some of the 4130 tubing and chucking it in the lathe and polishing it with steel wool. I then printed out a copy of the original receiver I had drawn in my cad program after finding a worthwhile blueprint of the receiver. I took this and glued it in place on the receiver and began cutting all the slots necessary. I left the material long and did not trim it to size until the machining was all done.

First, the magazine well

Next, the slot for the bolt/sear/hammer assembly on the bottom

A bad pic of the bottom of the receiver so far. The flash makes it look like it has been cut all the way through. It wasn't, the long slot on the bottom stops a couple inches shy of the mag well.

The ejection port. That funny looking knurled thing below the receiver is the thread-on end cap that holds the main spring in place.

Now, a slot on the top for the rear sight. Originally, the rear sight is what keeps the bolt aligned and keeps it from spinning in the receiver, as there is a flat running along the top of the bolt that meshes with a flat area on the bottom of the rear sight. The rear sight is also to be riveted in place.

Rear sight held in place
 Now, the receiver has the main areas that need machining taken care of. Now I can move on to trimming the receiver to the correct length. I didn't include any pics of the parting off procedure because it's a huge pain in the ass to part off metal to begin with, and holding a camera while dodging huge chips of metal sucks even more.

Now, once the receiver is trimmed to an overall length of 10.625", I turned the rear-most end down to an overall diameter of 1.46" to match the original receiver.

Next, I set the gear box on the lathe for 20 threads per inch, just like the original receiver has, and began threading. The reason you don't see the rest of the receiver is because it is inside the headstock of the lathe behind the chuck. That is one of the advantages of this newer lathe.

Threads rough cut, just a couple more passes at .001" each to clean them up,

And, the original receiver cap threads on snugly and cleanly.

Here I'm mocking up the receiver in the original wooden buttstock, with the mag well pieces I salvaged from the old receiver in place. A drum mag was used to get the spacing correct. I found out (almost too late) that if you set up the receiver for a stick magazine, the drum won't fit due to it being thicker than the stick mags. While the stick mags give you a healthy 36 rounds of 9mm on tap, what fun is it if you can't have a 72 round drum? So, a drum is used for mockup and tack welding.

Ignore the coat hangers. This is my garage, after all. I have to deal with having a dryer for a temporary workbench, and the significant other has to deal with having gun parts and tools all over the dryer.
 The receiver with end cap screwed on, drum in position, rear sight mocked up, and mag well tacked in place.

Some buzzing and zapping noises later, I had the mag well pieces MIG welded in place. Normally, these are riveted in place on the original receiver, however I see no need in riveting them on to the new receiver. No sense in making more work than is necessary.

That weird thing on the end of the receiver is the quick lock mechanism for the barrel housing. These have a quick release barrel assembly from the factory. I have to slightly modify the way this works so that an original barrel cannot be used on it to stay within the law. Reason why is because the original barrel is only 12 inches long. That constitutes a short-barreled rifle.
 Had to run uptown to get some parts from the local Horror Freight. Took Chloe the dog with me. Apparently, she loves car rides but gets bored from time to time.
 Anyway, the receiver is more-or-less done. I have to machine another part that slips inside the receiver right above the mag well so that the bolt and extractor will work in harmony with the barrel feed ramp, but before I do that, I have to modify the whole barrel assembly so that a short barrel will not fit on. Should I have a completed receiver sitting here that has the capability to accept a short barrel AND I have the short barrel sitting here (which I do), I would be breaking the law under the BATF's "constructive possession" law. So, I modify it so that a normal short barrel will not work, then finish the other part of the receiver.
I've mentioned before that in order to build some of this stuff, it takes me longer to do it in compliance with inane laws than it would otherwise. This last portion is an example of that. I have to do ____ before I can do _____ because otherwise I've built a/an machinegun/shortbarreled rifle/AOW/noncompliant light fixture/Improvised Explosive Device, etc.

Now, with that said, I do want a short-barreled rifle or two, I do want a AOW weapon, and I do want a machine gun. However, I will be going through the proper NFA channels to do so, and will pay my 200 dollar tax on each of them. It just sucks I have to do a bunch of mental gymnastics and odd preparation to ensure that at no point am I in violation of any silly laws.
Tomorrow I hope to work on the .50 BMG extractor, so it may be a few days before I pick back up on this Suomi, but I plan to have it finished pretty quickly.
More as I build it...............

Wednesday, February 16, 2011

The striker works

Not the best video, but for a phone I guess it does okay.



I had a lot of fine tuning to do to get the Holmes striker design to work. I must admit that on my next rifle build I am not using this design. It works, but man is it a pain in the butt to get this thing working 100%. Even now I am not totally happy with it, but it does work.
In case it is not completely evident, there is a notch cut in the rear bolt sleeve that permits a angled section to travel into. This angled piece prevents the firing pin from traveling all the way forward and striking the primer unless the bolt is rotated down, exposing the notch in the bolt sleeve.
Attached to the firing pin assembly is a piece of .5" thick 4140 steel that threads on to the firing pin and the angled piece threads into this piece of 4140. As the bolt is rotated upward and pulled back, the angled piece keeps the striker from rotating. The bolt is then pulled rearward and a new round is inserted, then the bolt is moved forward. As the bolt moves forward, the sear catches the striker and compresses the spring on the firing pin as the bolt is pushed forward and rotated downward. Pulling the trigger moves the sear downward, releasing the striker and allowing to travel all the way forward and hit the cartridge primer, firing the round.

Now that the striker works, the only machining left is the extractor, and my end mills still aren't in yet. I've got some finish work to do around the trigger group housing and then  some Duracoat is in order. Hopefully that will all get worked out next week. For now, the striker works, the trigger pull is decent, and the firing pin dents primers.

Tuesday, February 15, 2011

.50 BMG bolt work

 Okay, so the weather finally cleared up enough in my neck of the woods that I could get out in the garage and do some work without freezing to death. I wanted to get the extractor done on the bolt head, but found that the only end mill I had of appropriate size was broken. I ordered a new set of end mills, a new vise for my mill, and a handful of other odds and ends from a big name supplier whom I will not mention here as I want to remain civil despite their inability to keep track of their in-stock supplies. Suffice to say that they wanted to charge me for my order and not ship any of it until it came in around March 26th. I have had good luck with this company in the past, but I didn't care for the way they handled this one. I had heard a few good reviews about another business of similar nature named Wholesale Tool. They too sell good American and decent import tools at reasonable prices, and they have a shipping/store hub in Oklahoma. Good enough for me.
I went through and ordered the same parts as I had with the other tool supplier, but this time came out at a lower overall price, even with 3 day shipping via UPS. I received a phone call within 24 hours informing me that they did not have all the order in stock at the Oklahoma hub, would I mind if they shipped it 3 day UPS from another store located in Massachusetts, with no extra shipping costs to me, despite the difference in distance? Sure! They also informed me that I could get the order from Oklahoma within 3 days even if I elected to pay for normal ground shipping since it was so close to me. Apparently, these guys don't mind saving me some money. I will certainly be back to purchase tools from them if they stay true to their word.
So, the end mills should be here mid-week so I can get started on the extractor. Until then, I figured I would work on the striker assembly some more and make a bolt handle.

The bolt handle is really nothing special. I used a ~5.5" length of the .625 OD M2 drill rod I purchased a couple weeks ago for this. It was center drilled and chucked up in the lathe using a 3 jaw chuck and a live center. I turned one end down for 5/16" coarse threads about an inch long that would thread into the bolt, then reversed the part in the lathe and turned it down for 1/4" coarse threads that would thread into the knob on the end of the handle. I had to break out the calculator and figure out exactly what angle to set the lathe compound to, in order to go from a .625" OD to a .24" OD over a span of 3.5". I set the compound to the correct angle, then used the compound to turn this very gradual taper over the length of the handle. I also turned down a small section .25" in length, .51" in diameter behind the 5/16" threads so that the handle would fit in the .565 bolt slot of the receiver.

Finished part with 5/16" threads, about to run a die on the other end for the 1/4" threads.

 With all the threads cut, the lathe was sped up to about 1500 RPM and a piece of 100 grit sandpaper was used to smooth out all the tool marks before some scotchbrite was applied to polish it up and remove the sanding scratches.

Next up was the knob for the end of the handle. For this I used a piece of 1" OD 1080 hot roll steel I had laying around.
I started by center drilling the stock, then drilling it out in preparation for 1/4" threads. I then began  turning it down about .05" to remove the hot roll coating and get the outside surface completely devoid of pits and surface irregularities.

Next up was to decide what the appropriate taper of the knob should be. There was no math involved here, the exact angle was totally arbitrary. All I wanted was for it to look "right". I guesstimated about 35 degrees should work, and set the lathe compound to the appropriate amount. Ignore the scored threading marks on the stock, that was from using this piece of scrap as a test piece to determine correct thread pitch on something else I was working on.
 A few minutes later, I had this.
 The knob was then threaded internally,  a small section was knurled fairly deep, then the whole part was parted off. As I parted it off, I did it in small steps so I could get just the tiniest of tapers to it. This would allow me to use a file and sandpaper to give the end of the knob a slight radius. Once it was separate from the piece of scrap stock, I threaded the handle together to the knob, and chucked it up in the lathe for sanding and polishing. I used a small file to shape the end of the knob and give it a slight radius before using more 100 grit sandpaper to smooth out all the tool marks, then polished everything with scotchbrite. The photos are a bit misleading, as once I was done with the scotchbrite none of the parts needed actual buffing.

The completed assembly:

The completed assembly installed in the rifle:

 The above video was just a test of the video camera on my phone, this was just me milling flats on the bottom of the bolt sleeves in order to clear the sear.
Hopefully I'll have the sear completely functional tomorrow or the next day so I can dry fire the rifle. Once that is done and the extractor is complete, all the necessary parts go out for hardening.
More as I complete it.