1911-ish progress

So I had me an idea.  One sticky point on my 1911-ish build is that I'm concerned that the mainspring housing pin hole area is pretty thin, and that on a printed lower it will break out and let the mainspring housing go flying.  So then I thought what if I just make the mainspring housing one piece with the grip frame?  That would give me some extra strength in the grip frame, and eliminate the worry about the MSH retainer pin breaking out.  The biggest problem I see with that is that the sear spring has to go on before the MSH, and the MSH keeps the sear spring tab locked in it's slot.  To get around that, I'd add some extra clearance so that I could slide the sear spring in from the top, and once it's tab is in the slot in the mag well, I'd put a pin through the grip frame so that the spring couldn't come out of the slot.  That extra pin would be captured by the grip panels.  Hopefully that makes sense.  Here's a few pics that hopefully will explain it a little better.

Looking from the back of the grip frame, the red pin fills the gap between the sear spring and the now merged MSH/frame, keeping the sear spring in place:

Looking from the front:

Nothing is as good as actually being able to look at the thing, so I fired up the old magic machine and printed some parts.   I printed one with the standard MSH layout, and one with an integrated MSH.  While I was at it, I printed a temporary frame to make sure everything fits together like I want.

The integrated MSH seems to work alright.  It's a bit of a hassle to assemble, but really, once it's together it'll rarely have to come apart.  I put it all together with my slide and barrel, and all the internal parts of the grip frame are assembled.  The yellow printed temp frame isn't really strong enough to hold any spring pressure so all the FCG parts except the trigger and sear spring were left out.  The pin through the grip frame retains the sear spring perfectly.

Starting to finish

I'm at that point where I actually need to finish my Uzi.  I'm going to start with the bolt, because it's the easiest thing to finish.  As much as I like the machined look, this is an Uzi, and Uzi parts shouldn't be bright and shiny.  I could have all my parts parkerized like the originals, but I don't want to deal with shipping and the cost.  Fortunately, there is another way(and it's really easy).

For the bolt, I'm going to use Precision Tool Black( https://precisionbrand.com/product-category/tool-black/ ).  It's a blackening compound for ferrous metals, and it's super easy to use.  Just wet the metal with it, and almost instantly it turns black.  Here's the bolt, about half way covered(picture taken with my potato camera in poor lighting by the sink).

The Tool Black can't compete with industrial black oxide coatings for durability and you'll still need to keep things oiled to prevent rust, but it also doesn't require any special equipment and it goes on at room temperature.  It's literally wipe on, wait a few seconds, and rinse off with water.  I generally use a chunk of scotch-brite pad as an applicator, though you can just dunk your parts in it too.  A little goes a long way, and you could get several whole guns out of a pint bottle.  After coating the parts, a brownish-black film develops that I buff off with dry paper towels.  The rougher the surface, the blacker it gets so sandblasted parts come out very black, and polished/smooth parts tend to be a very dark gray.  Here's how my bolt looked after being treated:

1911-ish

Even though my Uzi isn't done yet, and I have a thousand other projects going on at the moment, I decided to start another one.  Some time ago I made a complete 1911 pistol from scratch on the CNC.  On that one, the frame was made in two pieces, left and right halves, with some of the pins replaced with screws, as well as a few screws added in other places.  That made it very easy to machine in just a few setups.  It was mostly aluminum with 6061 for frame and 7075 for the slide, but it's just a 22lr so I wasn't really worried too much about strength.

I decided that I wanted to make one in 45acp though, as a proper 1911 should be.  I didn't want to do the left/right half thing again, not really trusting a bolted together frame in 45.  I could do it in steel and silver solder the halves together, but as mentioned several times in my Uzi build, I hate machining steel.  Making a complete one piece 1911 frame from any material involves a lot of odd setups and careful machining, and I am far too impatient for that.  The available 80% frames don't really hold much interest for me either, I like doing everything myself.  Fortunately, there's another way.

I'm going to be building this 1911 like the STI 2011 pistols.  It's going to use separate upper frame and grip sections.  I'll be using an off the shelf slide and Sarco parts kit for the hard parts, I'll CNC an upper frame from 7075 aluminum, and the grip section will be 3D printed.  I hope to have under $250 in the whole thing.  Here's the the CAD work I've got done so far.  All the important bits and anything that needs to be very precise is in the upper frame, and you can see how the upper and lower will be split:

I'm reasonably confident that a 3D printed grip section will be strong enough, all the real load bearing areas are in the upper frame.  The area around the front upper grip pin and trigger guard is much thicker than standard, and the sides of the mag well have a big rib going down them to add some extra strength to the print.  The only part I'm really concerned about is the pin that holds in the mainspring housing.  The pin hole area is thin to begin with, and I think it'll break on a printed part(that's the little hole on the bottom right of the grip frame in the pic).  Fortunately, I have a plan for that too.  I'm probably going to make the grips from aluminum.  The top grip screw attaches to the upper frame and the bottom goes into the lower, so I'll basically have metal supports running the full length of the grip frame.  I'm going to make the grips so that the mainspring housing pin goes through them too, giving it some extra support.

I'm going to try not to drag this project out too long...

I may look stupid, but I'm not dumb

So I finally got all the pieces of the Uzi made and fitted, and working the way they're supposed to.  The only thing left to do was test it before paint(because I didn't want to paint it and find out I still had to grind on something).  While I am prone to making poor decisions, I try not to do dangerous things with guns.  Especially guns that I've made.  Double especially guns that I've made that have essentially just sheetmetal between explosions exploding and my face.  So what's a guy to do?  Get a long rope and hide behind a tree of course.  So I clamped the gun in a portable workbench and tied a rope around the trigger and pulled it from behind a big tree.

Started with one round in the gun to make sure it wouldn't explode, then stepped up to two and then three to make sure it worked as a proper semi-auto.  So how did it go?  Well, it didn't explode, and every round that it chambered fired.  But it also didn't work great.  Just about every other round FTE'd.  Stovepipe after stovepipe as the spent casings didn't want to leave the gun.  I also noticed that the casings that did properly eject didn't go far, maybe a foot or two.

I spent some time troubleshooting, tweaking my top cover clearance(which should be around .010" ), making sure everything moved nice and free, testing both mags I have and getting the same results, and finally thinking that maybe my new bolt actually needed the big ejection scallop cut in it that the factory semi Uzi bolts have(which I very much didn't want to add). 

And then I remembered to actually watch the video I'd taken.  Seeing it in slo-mo, it was clear that the bolt was short cycling, i.e. not going back as far as it should.  Between the short cycling and the spent casings not ejecting with any real force, it occurred to me that maybe the gun was fine, but the ammo wasn't.  Up to that point, I'd been using some Armscor 124gr FMJ that I bought many years ago but never used when I started a Suomi project(that never got finished...).  While it's probably fine for other 9mm guns, it just didn't seem zippy enough for the heavy Uzi bolt.  So I bought a box of Winchester NATO 124gr FMJ, which the internet told me was pretty hot, and my FTE problems went away.  Not only were the cases ejecting, they were now flying out and landing 8'-10' away.  Let that be a lesson, if something seems amiss with a gun, try some different ammo first.

What grade is this bolt?

Last time I posted about the Uzi, I started machining the bolt.  In what I'm sure will be a shocking surprise, in this post I'll finish it.  I got all the sides machined last time, all that's left are the ends, and just like a loaf of bread, the ends are the worse parts.

This operation to finish the back side of the bolt is one of the most nerve wracking things I've done in a long time.  All there is to it is a little bit of 3D machining, and drilling three holes.  Why was so nerve wracking?  Because the hole for the recoil spring is nearly 6" deep, through moderately hard steel, with a less than ideal coolant situation.  After more painfully slow machining/drilling with very small pecks and full retractions between pecks, it was done.  The Z axis got a workout that day, I tell you what.

With that done, there was only one operation left, but it was the most critical.  The Uzi being what it is and working the way it does, it generally doesn't require much precision.  This last operation is the only one that that really matters and it has to be exactly right.  Trimming the front end of the bolt and machining the bolt face is what will set the headspace for the gun.  Without having the headspace right, the cartridge case could rupture and the gun blow up.  It's not quite as critical with a blowback as it is with a locked breech system, but still important.  Finish drilling the recoil spring hole was no biggie but of all the painfully slow machining I've done, what's next was the slowest.  I wanted to avoid chatter in the cartridge recess/bolt face as much as possible.  To finish machine the bolt face, I had to use a 5/16" cutter hanging out of the collet 4", spinning at just a few hundred RPM, and stepping down a whole .010" at a time.  Then I had to drill the hole for the firing pin tip, and my long collet only cleared the side of the bolt by .020".  Know what's fun?  None of that.  But it worked and got the job done.

I actually did one last manual operation once the CNC work was done.  I located and drilled the through hole for the extractor retainer pin on the mill by hand.  It crosses the extractor hole off center and to drill it first might have made the extractor drill bit wander.  All in all, I think it turned out alright.  For something I reverse engineered with a calipers and machined in a tough material that I'm not very familiar with, I'm satisfied with the results.  Here it is next to my original IMI bolt:

It's fun to play dress up

I keep looking at the original Vietnam era Colt M16A1 parts kits, but they're always really beat and a lot of money for what you get.  I mean, you can get a whole, complete, new AR-15 for what an M16 parts kit costs.  Even cheaper than that though is my EBR, a Mossberg 715T.  The 715T is already just a 22lr dressed up in an AR-15 shaped plastic shell, and I decided to dress it up even more.

The 715T being just a 22 in a plastic shell that it is, standard AR/M16/M4 pattern parts won't fit.  In keeping with my general theme of "lets see how cheap we can do this," I decided to use airsoft parts with 3D printed adapters.  Some airsoft parts are surprisingly high quality, those guys get as into their hobby as we get into ours.  For my dress up kit I'm using an ICS stock, but just about any airsoft M16A1 style stock should work as long as it's the style with a the long screw attaching it. For the front end I'm using a JG/Golden Eagle M16A1 handguard. The whole conversion only cost me about $40 for the parts.

Here are all the printed parts that are needed:

And here's where they go on the rifle:

The handguard adapter holes are sized to be tapped for 8-32 socket head screws. The stock adapter hole is sized to use a 10-24 screw. I didn't have the long original screw for the stock so I made one with some 10-24 all-thread and welded a screw to the end to hold the stock on. It ended up being around 10" long, basically all the way from the butt plate to the 3D printed adapter.  The front handguard cap gets screwed to the front sight post with an 8-32 screw, and the front of the handguard needs to be trimmed slightly for screw clearance like so:

The front sight post and handguard cap should be a tight slip fit over the barrel, and the original 715T sling swivel will still work. I use an optic anyway, so the front sight is just decoration for me and a little bit of movement is ok, but it you use iron sights the front sight post has two holes in the bottom for 4-40 set screws if you really want to lock it down.  Some versions of the 715T have a threaded barrel so an actual flash hider can be bought cheap and threaded on, but mine is unthreaded.  My flash hider is printed solid and is meant to be a tight press fit onto the barrel.  It took a lot of force to to get mine pressed on, and it should be more than enough for a 22lr.  It's also pretty much just for decoration anyway.  The handguards need to be glued to the two handguard adapters too.  I used hot glue, but superglue would work just fine too.

When everything is printed in black and assembled, here's what we end up with:

If you happen to have one of these rifles and want to dress it up, my printable files can be found here: https://www.thingiverse.com/thing:3610994

I hate machining steel.

Now for the hardest part of my "doing it the hard way" Uzi project, the bolt.  There are a lot of differences between semi-auto and full auto Uzi bolts, primarily because of the striker instead of the fixed firing pin.  I could have bought a factory semi-auto bolt, or I could have modified my original bolt, but as previously discussed, I'm an idiot and apparently a glutton for punishment.  I decided to just make my own.

I made a CAD model of my FA Uzi bolt, then added the necessary modifications for semi-auto use so that I could CNC machine it.  The factory Uzi bolt is 4130 steel, but I decided to make mine out of A2 tool steel.  I chose A2 because it machines alright, it's very tough without being too brittle, and most importantly, I have a large chunk of it.

I hate machining steel.  Nothing about it is any fun.  It's hard on cutters, it's painfully slow compared to aluminum, and the chips are tiny little razors just waiting to bury themselves in your skin.  I'm also used to machining aluminum but very little steel(and even less hardened steel) so I run steel very conservatively.  My little CNC mill is not fast, and it is not powerful, I could never run aluminum at the speeds I'm used to.  But for steel, I don't need high speed anyway so it works out alright.  I use carbide endmills for everything because life is too short for high speed steel, and even good carbide is cheap these days.  Also machining high speed steel with high speed steel cutters is likely just going to chew up cutters so carbide is cheaper in the long run.

My new bolt is going to take 5 setups to machine, basically machine a side, turn it in the vice, machine the next side, and so on.  I don't need to machine the top because it's already flat.  After several hours of painfully slow machining, it's starting to look like something.

Operation 1, the right side:

Operation 2, the bottom:

Operation 3, the left side:

The last two ops are the important ones, and also the most nerve wracking, so stay tuned.  Same Bat time, same Bat channel!