SCR-ish update

It's funny how fast time gets away from you.  It's been almost two years since I stared my 3D printed SCR style bolt action AR project.  It seemed like I was always waiting for something and time kept creeping by.  In that time I've had a lot of people asking me for the files but I didn't have them ready yet.  None of the people that I gave the files to for beta testing followed through.  I also wasn't super happy with how the safety detent worked, so I wanted to do some more work on it.  I had enough parts to put together a 2nd one of my own, but didn't have the motivation. 

I've also been shopping around for another 22lr to plink with lately.  Then I saw Bear Creek's Black Friday ad advertising their new dedicated 22lr upper.  The lightbulb went off and I bought one.  My SCR style rifle was designed to be a bolt action because there was no room for an AR recoil system, and I wasn't super keen on replicating the real SCR's setup on a 3D printed receiver.  But, 22lr ARs don't need the stock recoil system, it's self contained in the upper.  So, I printed out the receiver and buttstock parts, and pinned on my brand new Bear Creek 22lr upper.  I've gotta say, this thing is great and a lot of fun to shoot.  The bolt/barrel setup is proprietary to Bear Creek, but the mags are CMMG and RTB compatible so mags are easy to get.  The optic is a $30 Amazon red/green dot because I love cheap optics on cheap guns.  I don't have a whole lot of rounds through it yet, and so far it's functioned flawlessly.  I hope to actually get the files posted on Weapons Guild by New Years.

PSG-Done

It happened again, I fell off the face of the internet.  Life, work, and whatnot.  Anyway, back to our regularly scheduled program.

I actually finished the my PSG-1 clone, the PSG-None(because there are no actual PSG-1 parts on it), back in April.  I took the pictures, and then left them to stare at me from my desktop for the next 8 months.  To recap, this is an Apex CETME C kit and barrel on an RTG G3 receiver flat bent on the 3D printed jig I designed, PSG-1 style reinforcement rails made by me, with 3D printed PSG-1 style furniture designed and 3D printed by me.  This is a low dollar build and I've had good results with cheap optics before, so the scope is a $35 CV Life from Amazon with a 3D Printed TPU eye bellows.  I also converted a G3 UB training bolt to use with the DAG blue plastic training ammo(see details a few posts ago).  Without wasting any more words here's how it turned out(clamp on bi-pod just for pictures):

Years ago, I 3D printed a costume prop PSG-1 for a friend.  It wasn't overly accurate, but at the time I didn't really know any better.  Just for kicks here's a picture of the original print I did along with my actual rifle.

Still falling...block

Just an update on my 3D printed falling block rifle.  I had a question on how strong the 3D printed barrel threads will be, or how much force it would take to blow the barrel forward out of the receiver.  Someone much smarter than me did the math on the thread shear strength using the rough numbers for PLA, and came up with a minimum of 6,815 lbf, with "ideal" threads giving me 13,583 lbf.  That's well over the amount of force that the DAG training ammo can generate.

I think I've got my design far enough along that I can make a test print.  I'm not sure what I want to do with the top of the handguard.  I don't really want a top handguard, but it looks like it's missing something without it.  I can't make the front of the receiver smaller or longer because of the barrel nut.  I like the Space Cowboy look, so I might end up with some sort of optic mount(my Savage Axis barrel doesn't have a front sight on it anyway).  

La Llama XV esta completa

I'm done with my little Llama XV 22lr.  After test firing, I cleaned the frame and painted it.  I tried something new with the paint, and I'm not really happy with how it turned out, but it will do for now.  I tried to replicate the nickel plating on the metal as best I could.  I use Rustolium Chrome spray paint and topped it with a matte clear.  It looks ok, but it didn't seem to stick to the print well and it chips super easy.  Next time I'll try a base coat of SEM Color Coat under the top coats because that stuff sticks to prints great.  The entire frame as well as the grip panels are 3D printed and here's how it turned out.  It's easy to forget just how small the Llama XV is when you see it alone in pics, so I included my partially printed full size 1911-ish in some of the pics for scale.

Help! I'm falling... a 3D printed falling block rifle

New project time, because apparently I don't have enough projects going on...

Ever since I discovered the very low power plastic DAG 7.62x51/308 training ammo(10g plastic bullet with a total range of only 300 meters), I've been looking for projects to use it with.  I also decided that I wanted a lever gun of some sort, for no reason I can explain.  And, obviously if you're here, you know I do a lot of 3D printing.  So I decided to combine all three into a new project.  I'm going to 3D print a lever operated rifle specifically for the DAG training ammo.

I want to use as many 3D printed parts as I can, mostly because I don't feel like machining anything.  "Locked breech" and "3D print" don't generally go together, so I decided to go with a single shot falling block action because of it's high strength in a smaller size.  With a falling block, it's easy to get a whole lot of strength without having a massive receiver.  It's also a very simple action with very few parts(and if the print proves to be too weak, easy to replicate in metal).  I'm going to use an AR15 hammer/trigger, and a floating 1911 firing pin(mostly because I have all these parts on hand already).  The DAG training ammo has a smaller case head than standard cartridges, and the action is designed around that so standard 308 WILL NOT FIT.  For the barrel, I'm going to use one from a Savage because of the way it threads into the receiver with a locknut to adjust the headspace.  I'll also be using the 3D printed stock I designed for my SCR style project, mostly because I have it and it fits me well.

Still very much a work in progress, but here's how the action looks so far.  The "H" shape of the breech block gives me four locking lugs and a whole lot of surface area and shear area.  Napkin math using PLA numbers and the Lilja equation says that that the locking block should be able to handle 2100lb of bolt thrust with a safety factor of 2.  I have no idea how much power this training ammo has, but it's pretty wimpy, and for reference a 22LR makes about 900lbs of bolt thrust.  My biggest concern is that the case head might start crushing the plastic on the breechface, and if it does, I'll make a metal insert for it.

Here's how it looks with the breech closed and and ready to fire:

When the lever is opened, it pulls the block down, the nose of the lever then hits the extractor lever pulling the case out, and the block cams the hammer back to half cock(I'll cut a half cock notch into the AR hammer).  Once closed again, the hammer can be cocked the rest of the way with the new lever attached to it and sticking out the side of the receiver(which isn't ideal, but I can't come up with anything else that will work with the AR FCG).

Llamas spit.

I finally got my 3D printed Llama frame to were I'm satisfied with it.  It took 11 tries to get it right.  On a normal 1911, I'd have printed a few, got it close, then fit the parts to the frame like you would with any new frame.  That wasn't an option here though because Llama parts are hard to come by and I can't afford to screw anything up so I basically had to fit the frame to the parts.  

I had a heck of a time with magazines too.  Llama mags are expensive, and I'm not positive that they would work because the Llama grip angle is slightly different from the standard 1911 frame my print is based off of.  I tried to make a printed one...and mags are hard...  I ended up using a Browning 1911-22 mag.  The Browning 1911-22 is a similar size to the Llama, but uses the standard 1911 grip angle.  I had to add a little clearance for the slide stop, and file out the mag catch slot a little to get it to lock it, but otherwise it works great!

It actually works...and I didn't lose any fingers!  I put about 30 rounds through it before tearing it all down for inspection.  I had some trouble with light strikes, about 1/4 of the rounds needed a second smack of the hammer to go off.  New mainsprings are completely unavailable, so I'll take it out and do some measuring to find a replacement.  Because of limited space and unavailable parts, the ejector is part of the printed frame.  Though I don't have many rounds through it, the ejector doesn't show any signs of damage from the shells hitting it.

How to waste a day to save $30

You know, sometimes I do things that don't make sense.  Take the project in today's post for example.  I spent an entire afternoon on this, for the express purpose of saving a measly $30.  I wanted a 5rd magazine for my PSG-None because that's what real PSG-1's came with, and because it just doesn't look right with the 20 rounder.  20rd G3 mags are cheap, sometimes as low as $5 a piece if you shop around.  The 5 rounders though start at $30 for POF, and real HKs are much more.  The POFs are nice enough, but I didn't want to spend $30, so I decided to make my own.

I started with a completely stripped G3 mag and whacked the bottom off.

Then I trimmed some of the bottom to make some tabs to fold over.

The tabs need to be folded over very carefully.  Whatever kind of aluminum these mags are made from, it's fairly hard and will crack if you're not careful.

I also had to shorten the rest of the bits.  I cut off about half of the spring, and shortened the reinforcement plate and strap that go across the front of the mag.  I might take another wind off the spring, but I want to see how this one feeds first.

With everything trimmed,it goes back together like any other mag.  Here we are, one afternoon and 15 rounds less later: