AR Polymer80 Versus Forged 80%

BerettaOrSig

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Someone was asking me about my experience carving out an 80% and thought I could share the info I have.

I haven't carved a Polymer80 but from what I hear the plastic is a lot easier to work with. I'd also imagine it takes much less time, I spent at least 5 hours cutting the metal ones.

1. I've heard people say for the glock Polymer80 they use a dremel, file or a razorblade to hack off the nubs. This will require more effort to remove the material. At the very least a dremel, drill, or drill press (though I can imagine it is possible to use a wood chisel).

2. Finish. If you leave a little extra on the FCG walls you can file and sandpaper the excess so you have a really nice finished product.

3. The biggest concern, you don't want to take too much off by accident as the polymer is not as strong as metal.

4. Less noise. No sharp metal shavings everywhere, just plastic. No cutting fluid needed, and you're not going to break bits.

There are pluses and minuses.

On the other hand I have carved out some aluminum ones and I can tell you.

1. It can get messy. Metal shavings everywhere... and the cutting fluid coats everything in the immediate work area. I set up a shopvac to catch a good portion of the shavings. The router has to be on high speed so some of the shavings fly surprisingly far, setting up a cardboard box around the jig helps to catch fliers and some cutting fluid, it still covers my vice and table. Wear eye protection.

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2. It takes a lot of time. On the second one I got ahead of myself thinking it was going so smooth I can take off more with each pass. No, I tried to chew off too much and instantly snapped all the teeth off the $20 router bit.

3. Cost. The router, jig and bits alone are going to cost $500 or more. The 80% Arms Jig alone is $300, though it will last.

4. It is noisy, I wear earmuffs while doing it.

That said, they come out nice if you take your time. The metal ones are very strong, I get the forged 7075.

I bought the polymer because carved out, you can bury it and no metal detector is going to find it, as long as you hide the lower parts kit separately. I know they say their wonder dogs can sniff out polymer, well with the vast amount of shaving you'll have more than enough to spread around that they'd have to tear up your entire yard and still not find it if you hid it in a tree. So... that said, do you need to hide the upper and other parts, potentially. Though the lower might be the only part they outlaw. We know They are coming for the guns, one way or another. Not that you should break Their laws, just speaking hypothetically.

Sorry this was long but I wanted to be detailed so you can make an informed decision.

Anyone with more information, or any tips or tricks to use... it is appreciated.
 
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Golddiggie

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5 HOURS per lower?? WOW.
I've done an 80% aluminum lower in about an hour. That's with it ready for either Cerakote or assembly. Including the side holes drilled and reamed to correct size. Then again, I've always used a milling machine to do these (got one in my garage right now, and about 5 lowers I need to process).
Besides taking a fraction of the time you mention, I use zero fluid when milling (don't even use any when drilling or reaming) and don't have dust flying everywhere.
Sure, not everyone can have a milling machine, but if you have space for a good one, you'll FIND more things to do with it.
You need to decide what's more important to you, saving some money, or having 4+ hours of your life back per lower?
As for material strength, I'd trust the aluminum lowers far more than the plastic ones. I had a couple of plastic ones almost a decade ago now. Got rid of them when I could get the aluminum ones. IMO, they're OK for something like a 22LR build, but I wouldn't trust them to the same extent with anything larger (caliber wise). Especially not something larger/more powerful than .223.
 

BerettaOrSig

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5 HOURS per lower?? WOW.
I've done an 80% aluminum lower in about an hour. That's with it ready for either Cerakote or assembly. Including the side holes drilled and reamed to correct size. Then again, I've always used a milling machine to do these (got one in my garage right now, and about 5 lowers I need to process).
Besides taking a fraction of the time you mention, I use zero fluid when milling (don't even use any when drilling or reaming) and don't have dust flying everywhere.
Sure, not everyone can have a milling machine, but if you have space for a good one, you'll FIND more things to do with it.
You need to decide what's more important to you, saving some money, or having 4+ hours of your life back per lower?
As for material strength, I'd trust the aluminum lowers far more than the plastic ones. I had a couple of plastic ones almost a decade ago now. Got rid of them when I could get the aluminum ones. IMO, they're OK for something like a 22LR build, but I wouldn't trust them to the same extent with anything larger (caliber wise). Especially not something larger/more powerful than .223.
That's great you can bang them out in an hour... it doesn't help me. Can we see a picture of how nice one came out? I'm not saying it can't be done, I'm sure it can, but I don't care to rush it. I clear all the chips away after every pass. It takes time.

Per the 80% Arms instructions they recommend cutting fluid. The 5 hours is taking your time by hand. Even just drilling the pilot hole they recommend only 5-7 seconds at a time and clearing the hole and reapplying cutting fluid. So yes, take your time. I'm not in a rush to bang out 100 lowers.

A CNC machine would be nice but I have neither the space or the money.

That said, it is not about saving money. In fact, it costs a little more. But you don't have to tell the government or get a permission slip to exercise your right.
 

xtry51

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Using a manual mill, I can finish an aluminum lower in about an hour. If I just wanted to use my jig to do it with a hand drill and not care about what the trigger pocket looks like when done (which you would never see from outside anyway and has zero functional impact) I've finished one with a Dewalt cordless drill in under 20min.

I've never done a polymer one. I don't see the point unless you're making them yourselves at home on a printer or molding them at home.
 
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BerettaOrSig

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Using a manual mill, I can finish a lower in about an hour. If I just wanted to use my jig to do it with a hand drill and not care about what the trigger pocket looks like when done (which you would never see from outside anyway and has zero functional impact) I've finished one with a Dewalt cordless drill in under 20min.
That is true that it doesn't impact the function if it is not perfectly cut, so long as you are able to keep it clean.

I believe part of the reason it can take longer is to prevent the bits from heating up. 20 minutes, did you burn up the bit?
 

xtry51

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That is true that it doesn't impact the function if it is not perfectly cut, so long as you are able to keep it clean.

I believe part of the reason it can take longer is to prevent the bits from heating up. 20 minutes, did you burn up the bit?

Not even close. If you have cobalt bits, you can break a bit by bending it, bit you're not going to dull a bit on aluminum. Stay away from HSS bits. They are trash if you are drilling metal. Fine for wood/plastic work.
 
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As @Golddiggie said Aluminum is superior to the plastic. Glocks were made to be plastic ARs were not. That said James Madison Tactical has metal inserts in their poly lowers to beef them up. They keep improving the polys so try a polymer out to see how you like it. You are the one you need to please. The polys however cost more than aluminum.

It's not a race enjoy the ride and learn. The more experience you have the quicker you will be able to complete them.
 

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As @Golddiggie said Aluminum is superior to the plastic. Glocks were made to be plastic ARs were not. That said James Madison Tactical has metal inserts in their poly lowers to beef them up. They keep improving the polys so try a polymer out to see how you like it. You are the one you need to please. The polys however cost more than aluminum.

It's not a race enjoy the ride and learn. The more experience you have the quicker you will be able to complete them.
Agreed. JMT is good because it's reinforced, especially at the buffer insert (where most recoil pressure ends up). I would use it for 223/22lr, but not for 9mm since all the recoil force is directly on the bolt and not softened through a gas system.
I still think it's worth trying a poly. If it works, great, you have a lightweight lower. If not, oh well $100 was worth a shot, back to aluminum.
 

ReluctantDecoy

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I don't doubt modern poly lowers can handle moderate (maybe not duty) use for AR lowers, but I have my doubts about 80% versions. They're still glass fiber infused polymers. It's one thing to create an AR lower mold for glass infused polymer injection to create a monolithic structure, and entirely another thing to take a glass infused polymer lower and cut into it, thus breaking monolithic glass structure. For aluminum, there is enough material strength where that doesn't matter. For polymer, it could make a noticeable difference.
 
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I have never cut a polymer receiver, or even considered finishing a polymer gun.
Aluminum and steel is what I like. For AR lowers I made a holding fixture from a set of aluminum soft jaws for my mill vise to do the pockets. For the side holes the AR receiver is easily held on its side squarely in a vise. The holes are then located using coordinates with either a dro or knobs on the milling machine.
For cutting fluid, good old WD40 is hard to beat. Clearing chips while cutting pockets is very important, it keeps recutting swarf to a minimum. That will keep the heat down and help to make your cuts on size.
Obviously this is how I do it on a mill, but clearing chips and using WD40 will help if using a jig as well.
A few things that I have on the burner are a Glock mag PCC lower, a forged steel 80% 1911, and I want to make a 10/22 receiver from scratch.
I got lots of 0% receivers laying around my shop!
 

hminsky

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I had a pretty good experience with a polymer lower right up until I got to drilling the holes for the safety, and
it came out slightly off center. I should have taken the advice about using a hand drill rather than a drill press for that
operation I think.

Anyway, like someone said above, I'm a little suspicious of milling out a fiberglass/polymer block around the narrow parts, it just
seems like too fragile and would break some time. At least with Aluminum you can sometimes bend it back into shape if it gets smacked.
If the polymer cracks, it's kind of over.
 

BerettaOrSig

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Not even close. If you have cobalt bits, you can break a bit by bending it, bit you're not going to dull a bit on aluminum. Stay away from HSS bits. They are trash if you are drilling metal. Fine for wood/plastic work.
I definitely put too much pressure on a cobalt bit and it blew all the teeth off when it hung up. Interesting, from what I've read I didn't know you can't dull the cobalt on aluminum, even if it heats up huh.

That said James Madison Tactical has metal inserts in their poly lowers to beef them up. They keep improving the polys so try a polymer out to see how you like it.
Thanks, I will look into it. I'm glad someone is finally making a metal reinforced lower.

Agreed. JMT is good because it's reinforced, especially at the buffer insert (where most recoil pressure ends up). I would use it for 223/22lr, but not for 9mm since all the recoil force is directly on the bolt and not softened through a gas system.
Yeah, I agree that it can be beneficial in some applications in reducing weight and ease of building a lower.

Some people can't afford the equipment to mill out an aluminum lower. So drilling a polymer is pretty straightforward.

I haven't built any 9mm AR's... I know, I know, but I just haven't seen a reason to. I have multiple Beretta 92's and multiple Beretta CX4's that have interchangeable mags, are pretty compact, I like the feel and function, and I got them cheap.

So I don't know how that setup functions for a 9mm upper. From what you're saying I figure all the pressure is used from the chamber to push the bolt back and cycle the firearm. Though I don't see how that would be worse for a poly lower? Isn't a 9mm going to apply less pressure than a .223 rem cartridge. I don't have any but it should take pressure off with a piston driven upper for that matter?

Lastly, it would add stress to the buffer threads using a light poly lower to make an AR pistol because you wouldn't be shouldering it.. and the increased short gas system pressure, and for a suppressor too.

Well, that is a bit to consider.

Glad we are having this conversation.
 

SKumar

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So I don't know how that setup functions for a 9mm upper. From what you're saying I figure all the pressure is used from the chamber to push the bolt back and cycle the firearm. Though I don't see how that would be worse for a poly lower? Isn't a 9mm going to apply less pressure than a .223 rem cartridge. I don't have any but it should take pressure off with a piston driven upper for that matter?
Put it this way: if polymer AR lowers were that unreliable, we'd be hearing about it by now (and I'm sure the market would've responded). Sure you'll get a failure here and there, but there are thousands of good examples made. I think you'll be fine with 9mm, especially if you get the buffer weight correct (I would start with 8oz off the bat).
 

xtry51

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Well if you had a 5k or more spindle CNC you can f*** up a cobalt drill tip no prob, lol. But we're talking about garage hand tools and maybe a 1/2hp drill press or manual mill. I have a full set of number/letter/fraction cobalt drills I bought 15 years ago and I've replaced maybe 10 of them in all that time.
 
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Well if you had a 5k or more spindle CNC you can f*** up a cobalt drill tip no prob, lol. But we're talking about garage hand tools and maybe a 1/2hp drill press or manual mill. I have a full set of number/letter/fraction cobalt drills I bought 15 years ago and I've replaced maybe 10 of them in all that time.
I have had my machine tools for about 5 years now. Since then, I have learned a tremendous amount about cutting metals and plastic. I look a drilling holes completely different now compared to when I just had a drill press, a hand drill, a chop saw, and a welder.
When using drill bits, especially smaller ones, it is really important to withdraw the drill to clear the chips before the flutes are full, and apply cutting oil before you start to drill again. This is called pecking. It keeps the drill cutting and not rubbing. It also keeps the drill and the work from overheating, which is very bad for the drill bit and the part you are working on.
This axle is 12" long. The hole that I drilled down the center of it is 9" deep. That is a 3/16 drill bit. I drilled that deep hole using the pecking technique described above. Over on the mill I drilled 4 ,1/8" out holes for grease to lube 4 bearings that are in direct contact with the axle.
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One other very important thing to know about drilling holes in metal is rpm's. Generally you turn smaller bits faster than larger bits. Ballpark rpms for drill bit sizes that I use are 1/8" to 1/4" is 700 to 800 rpms, 5/16" to 1/2" is 400 to 600 rpms. 250 to 400 rpms for bits up to 3/4". Anything over 3/4" you really need a machine that can turn 100 to 150 rpms and has some muscle. You won't find power tools at Home Depot that can turn 100 rpms. But most home owners dont need to drill a 1" hole into half inch thick steel.
If you guys are wondering, yes it is really tempting to make a supressor, solvent trap, or an oil filter adapter with my machine tools. I have had people ask me to finish an 80% gun for them. I tell them no f'ing way am will I mess with that stuff, not worth it.
 

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My milling machine has a 2HP 240v motor on it. Geared speed selection starting at 90rpm. It has six speeds to pick from (3 per low and high range, max speed is 1970rpm) that work for everything I want to machine. I typically set the speed depending on bit cutting diameter, flute count, and material being machined. Plus if it's a finishing pass or not. When I was making the beer can filler base a couple of weeks back, I was using the two highest speeds available. The lower of the two to make the deeper cuts and the highest speed to do a finishing pass (much lighter cut). That was also in aluminum with a 5/16" end mill.

When I've finished lowers, in the past, I've used a 5/8" end mill in the trigger/hammer area and smaller ones (7/16" and 1/2") for the other parts. Hit the corners with either a 7/16" or 3/8" to give them nice and tight radius. I also have DROs on my mill, so I don't need to use the dials to figure out how much of a cut I've made. DROs help since they [basically] negate any backlash when switching directions. Since I have a 'benchtop' mill (at 650# by itself you're not going to move it around) I have a three axis DRO. I put one of the scales on the spindle indicator so that I can get an accurate cut depth. I don't have anything on the mill head (dovetail movement) since that's of far less interest.

As I mentioned before, time to finish a lower is about an hour. I've also not used ED40 or anything else during the process. But, I do have a shop vac to suck the chips up out of the pocket as it gets created. I actually do that for pretty much anything I'm machining. Hell, I even do that when I'm doing a facing operation to keep the item cleaner. It's pretty easy with my current setup.

I could see, eventually, getting either a knee mill or a CNC machine. That's at least a few years in the future though.
 

BerettaOrSig

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Heh, yeah... so having zero previous experience with milling anything I bought a Bosch router for the 80% lowers. It came with a standard base, plunger base, and a table attachment so I can learn how to use it on wood at some point as well. It was under $300.

That is some pretty sweet machining equipment you guys have.

Thanks for the tips, I will look into getting some different bits and improving.
 
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3. Cost. The router, jig and bits alone are going to cost $500 or more. The 80% Arms Jig alone is $300, though it will last.

Way back when I was preparing to do some "0%" and "80%" lowers, I had looked into some of the jigs available. I just ended up buying a used RF45 benchtop mill/drill instead for $600. My "shop" space is tiny - about 6' x 10', so couldn't go with a "real" mill. I've since made all kinds of toys with that little mill. Was definitely a better buy than the dedicated AR jigs.
 

BerettaOrSig

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Way back when I was preparing to do some "0%" and "80%" lowers, I had looked into some of the jigs available. I just ended up buying a used RF45 benchtop mill/drill instead for $600. My "shop" space is tiny - about 6' x 10', so couldn't go with a "real" mill. I've since made all kinds of toys with that little mill. Was definitely a better buy than the dedicated AR jigs.
How do you mill it out with that time of equipment, do you have to make measurements and adjust how far it mills on the x, y, and z axis?

I see what you're saying, I paid the same and the jig is only useful for making AR lowers. I just didn't feel I'd use such a machine for anything else. Except some woodworking I can use the router for.

Lastly, for someone like me with no experience milling the jig makes it stupid simple. I actually had the lowers for a while and didn't mill any until I dropped one on my cement floor and got some good deep marks... then I figured, what the hell, lets try it out.

So the big question is, would you recommend it for someone with zero experience?
 
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How do you mill it out with that time of equipment, do you have to make measurements and adjust how far it mills on the x, y, and z axis?

I see what you're saying, I paid the same and the jig is only useful for making AR lowers. I just didn't feel I'd use such a machine for anything else. Except some woodworking I can use the router for.

Lastly, for someone like me with no experience milling the jig makes it stupid simple. I actually had the lowers for a while and didn't mill any until I dropped one on my cement floor and got some good deep marks... then I figured, what the hell, lets try it out.

So the big question is, would you recommend it for someone with zero experience?

With a mill, you set up your workpiece on the mill's table, find a "zero" location (on an AR lower - say the centerline of the pivot pin hole), and work from that point as a reference. I did the "0%" raw forgings just by counting turns of the handwheels. You have to pay attention to not lose count. Then I got some digital readouts (DRO's), and the "80%" ones were easy.

I also thought I'd just use the mill to do some AR lowers - but then it got to be fun, so made a 1911 frame, AR10 lower, FAL receiver, semi-auto Suomi M31, STEN MK3 and Lanchester MK1*, and working on a bunch of other stuff. It can get sort of addictive. :cool:

I didn't have much experience with a mill either, just started hacking away at stuff and learned as I went.
 
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With a mill, you set up your workpiece on the mill's table, find a "zero" location (on an AR lower - say the centerline of the pivot pin hole), and work from that point as a reference. I did the "0%" raw forgings just by counting turns of the handwheels. You have to pay attention to not lose count. Then I got some digital readouts (DRO's), and the "80%" ones were easy.

I also thought I'd just use the mill to do some AR lowers - but then it got to be fun, so made a 1911 frame, AR10 lower, FAL receiver, semi-auto Suomi M31, STEN MK3 and Lanchester MK1*, and working on a bunch of other stuff. It can get sort of addictive. :cool:

I didn't have much experience with a mill either, just started hacking away at stuff and learned as I went.
I hope that you have a lathe too. You won't believe what a lathe is capable of.
 

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