Fun stuff first.
I took the 3D printed lower to the range and tested it out. Ran fine.
When I first was thinking about doing this project, I expected to 3D print a gun, then shoot it until it broke. After I printed the Gluty lower, I realized if I tried to do that I would end up shooting all my ammo, that would be kinda hard to replace right now.
I fired 190 rounds, I stopped because the handguards got very hot. I did have a couple of minor issues. The first mag I tried was a Lancer mag (I think they have a new generation, if so, this is a first gen mag). I over inserted it and had a hard time removing it from the gun. So I didn’t use the Lancer mags, and instead used a USGI mag and four Magpul 40 round mags. One of the Pmags did not have the follower come up completely causing the bolt to fail to lock to the rear upon firing the last shot. I would call this a mag problem, not a gun problem. I’ve previously reported about having these issues with my Magpul 40 round Pmags.
I have no doubt, that with quality magazines, I wouldn’t have had a single issue.
Now let us back track.
I was printing the Gluty 9mm pistol. It would use a Glock barrel and mags, and the bulk of the chassis would be printed. While the bolt is in a printed shell, it is mainly a big hunk of steel rod with a notch cut out of it and holes drilled though it. The work can be done with a Dremel and drill press, but most of my tools are packed away in my horder’s nest, so I decided to pivot to a simpler project. An AR15 lower.
There are a number of good options. I had a hard time picking which one to print, finally picked the “Aliamano Phobos AR-15 lower”, made by ArmaDelite, which is “based on the JT-Vangard and Phobos models”.
This one was picked because it looked like it would be easier to print than some of the other options. I don’t know if that is truly the case, but it is why I picked it.
I was able to print it in a single piece, out of PLA+ filament.
Online, you can find many a person who says that ABS would be the better choice for printing a firearm. But when you read reports of people who are printing firearms using FDM printers like mine, they talk about ABS been weak along the layers and needed acetone or MEK welding, or other reinforcements. I’ve never worked with ABS in printing, so I decided to try PLA. That is also what I had on hand and I wasn’t about to spend money on this project.
I don’t so much printing with supports, so I tried settings the support material to be printed at a 45 degree angle to the main part. I hoped that would make it easier to remove. That was a mistake. Instead of peeling off in large chunks, the support material came off in very small pieces and I spent about 8 hours taking this print from the state it was off the printer, into being an assembled lower.
Pretty much all the holes had to be drilled out to size. With the exception of the firing pin holes, those came out perfectly in spec.
After 6 hours of scraping and peeling away support material bit by bit, the lower was still covered with it.
The worst part ending up being the threading where the receiver extension (buffer tube) goes. Some of the support material at the top would not come out at all. I finally had to take a sanding drum for the Dremel, melt away much of the plastic, and use a receiver extension to tap all those threads. That was miserable work, and I was afraid I was going to scrap the lower. I even got ready to print another one with different settings right before I finally got the receiver extension to screw in all the way.
I ran into a few other problems as well. The slot for the magazine catch printed undersize and I had to spend a while with a file to clean it out. Then I found the cheap old parts I had laying around were screw up.
I don’t know what brand that is, but it is a plastic mag release catch button I pulled out of an old AR15. It screws onto the match catch crooked.
So the mag release on this gun binds slightly. It works, but not as smoothly as it should. I could spent more time filing away plastic to account for this out of spec button and the tight slot in the lower, but it works. I’m not looking for perfection here, just functionality. “Anything worth doing, is worth doing poorly.”
The other issue I ran into was that when I went to tap the grip screw hole in the receiver, the tap I used just ripped the plastic out of that hole. Reaming it out over sized. I started to try a couple different solutions, finally decided to go an easy route and printed up an AR15 grip and glued it to the lower. I left out the spring and detent for the safety and I didn’t want to permanently leave them in this lower, and the safety is already quite stiff as it is.
A crummy fix, but it works, and that is the goal here.
Aliamano Phobos AR-15 lower
If I were to complain about this lower, I would have two main gripes. It is not compatible with an upper that has a forward assist, and the trigger guard is a little thin for something 3D printed, and I believe it would break under abuse. I feel like I could break it by hand. It wouldn’t stop the lower from functioning, but it could be much beefier.
A smaller issue is that the reinforcement make it a little harder to access the safety. I was able to quickly access the safety for rapid shooting drills, but it is no where near as easy as on a standard lower.
The massive reinforcement where the receiver extension screws into makes installing the receiver extension a major pain. I placed the receiver extension in a vise and use a wrench on the lower to turn it. Took a lot of effort. I was worried the lower would break. Turned out fine.
But the receiver is really wide in the back. You will want to use a larger, satellite dish sized, charging handle latch. I read that other people who have printed AR lowers tend to be fond of using side charging handles on them
“That just sounds like an AK with extra steps.”
This lower has a very cut away magwell. Over the years I have seen several ARs with cut away magwells and they have all functioned fine. This one is even more cut away. Inserting a magazine I found I could move it a fair bit side to side or tilt it forwards and backwards. So when shooting the gun, I tried tilting the mag back, forwards, left, right, and to the extreme diagonals, but I was unable to induce a malfunction during rapid fire.
I have no doubt this lower could withstand short term heavy use. But PLA degrades with time. Some like to push that PLA is better for the environment because it is biodegradable. Time, humidity, and high temperatures will all make PLA degrade faster. But it still is a plastic, and it won’t completely biodegrade any time soon under normal conditions.
I looked into the longevity of PLA printed parts, and I couldn’t find any hard numbers. I do know that stuff I have printed in PLA seems to get more brittle over time. So I am going to stash this lower away for a while and see how to holds up a few months from now.
It is likely that a PLA lower would hold up for several years.
Still for the time and effort involved, I think 3D printing firearms is more an exercise in novelty than a practical production. It does help show the futility of anti-gun laws.