Should I buy an 80% Lower?

[TanklessPro]

I have built several AR's including cerakoting them. I like doing gunsmithing and I'm considering getting some 80% AR lowers to play with. I know the cost is not worth it but I kinda want to try it. So what have y'all experienced?

EDIT: I forgot to add, I want to try it. If that's you please comment.

 

[Robert]

I have done 1 308 lowers and a few 5.56 AR lowers. With the proper jigs and a few tools it can be done. Heck it is kind of fun to do and I have a bunch of others sitting in a box next to the work bench. The 80% Arms jig is the finest on the market. I use a drill press to make the initial holes and then use a router and end mill to hog it out. Takes a while but I don't need a mill. Though I d love to have even a decent bench top mill.

 

[dirtengineer]

The Modulus Arms jig is better than the 80% Arms jigs. It is a lot of fun if you are a do-it-yourself type.

 

[Hacker15E]

Do it! It is fun and worth it, even if the end product is much more expensive and not as tight-toleranced as a factory lower.

 

[Candyman87]

If you're looking for a project, go for it. As long as you're not trying to save a few bucks

My future F-I-L is in the process of setting up some equipment for this... the process has been fascinating for sure.

 

[JSH1]

I don't see the point. Why pay more for a partially finished part? The only reason I can see is if you are looking to avoid the paperwork on a finished lower.

 

[TanklessPro]

I don't see the point. Why pay more for a partially finished part? The only reason I can see is if you are looking to avoid the paperwork on a finished lower.

I'm not trying to avoid anything. I'm wanting to do it for the experience.

 

[JSH1]

I'm not trying to avoid anything. I'm wanting to do it for the experience.

And that's fine. When I look to do something myself it is either to save money or because I know I'll do it better. I don't think either apply to 80% lowers.

I'm also an engineer so I get my fill of tinkering at work.

 

[yugorpk]

I'm also an engineer who could do all the work but the thought of paying 2X more for less plus an additional $600 of my time doesnt seem to be a good use of resources.

 

[Warp]

I can't vote because I would (why not?) but haven't tried.

Go for it if you want to, why not? If it's entertainment or learning/experience that has value.

 

[MachIVshooter]

If you have a mill, they're a snap, no jig needed. On my Lagun FTV-2, they come out looking like commercially finished lowers





If you don't, you'll definitely need a jig. The router based jigs seem to be optimal from the results I've seen. Lots of guys use a small drill press with a cross slide vise, but the rigidity isn't there, and drills are not designed for side loading (actually dangerous, as the JT or MT chucks can pop off). Also less investment in a router than a drill press and X-Y vise. You might wanna look over in the Arfcom "build it yourself" forum to see which jigs and routers people like best.

 

[USAF_Vet]

I voted no because regular stripped lowers are easy enough to come by.

Although, I would change my vote if I could. There was one option not on there.

I have not done an 80% polymer or aluminum lower. Although, I have done a flat steel puzzle piece weldable lower.

It's currently a paperweight, but I learned a lot in making those mistakes, so when I do another one in the future, it'll be functional. I might be able to salvage this project lower, though. I'll need to cut it apart and re-weld pieces back in better spots, as well as weld in a steel Uzi mag well for a 9mm project.

I'd change my vote to "I tried, failed it and it is now a paper weight....." but I learned and will do better next time.

 

[MaterDei]

I would like to try one (not an option on the poll)

 

[dogmush]

I've done several, and have a .308 waiting for me to have the time to finish it up. They are fun.

I say go for it.

 

[Redlg155]

Considered it, but haven't committed yet.

I personally think it would be more fun, and challenging making an AK reciever out of a shovel, which has been done before and something I definitely want to try!

 

[Zach S]

If you just want to try it, go for it. If you screw up, relax. you've probably made more expensive mistakes, and if you haven't, you will.

I've thought about it since I have access to a few Bridgeports at work. As a matter of fact, I've thought about finishing a raw forging to build a lower that uses my tommy gun magazines and Olympic .45 upper, but only because I couldn't find an 80% that didn't have the magwell and mag release cut out.

But i'm a tinkerer who has ideas that exceed my budget and time.

 

[Jackal]

Finishing 80% lowers is like sporterizing a milsurp rifle. Yes its cheaper to just buy a hunting rifle, but where's the fun in that? Its also cheaper to buy nothing at all.

 

[MachIVshooter]

As a matter of fact, I've thought about finishing a raw forging to build a lower that uses my tommy gun magazines and Olympic .45 upper, but only because I couldn't find an 80% that didn't have the magwell and mag release cut out.

Raw forgings are a pain. It's actually easier, IMO, to machine the whole thing from a chunk of billet. Virtually every dimension is based on the front pin hole; making from billet, you start there. With a raw forging, you have very little margin to properly locate that hole, or the whole thing is trash. Work holding is a big challenge with them, too, and trying to get them square is a difficult, the only semi-square spots on a raw forging being the sides of the FCG area. It's doable, but if you have the ability to finish one of those, you can probably make the whole thing. One fellow on Arfcom finished a 0% on a mini mill, and it worked out, but I imagine he had every bit of 50 hours in it with having to make fixtures and get creative with work holding on the small machine.

http://www.ar15.com/forums/t_3_4/672331_My_First_Attempt_at_a_Zero_.html

For your purposes, I'd say machine a mag well adapter and epoxy or mechanically fasten it in place.

 

[clearcut]

Building a 80% is vary rewarding,and comes with the confidence that you will know your AR inside and out.Save money ??? I don't save reloading but I shoot more! I have a new 80% here on my desk and I cant wait to start on it, I just use an X Y vice and drill press and that works for me.This will be a 300BK

CC

 

[giggitygiggity]

When you can get lowers for $40 from AIM Surplus, it makes no sense to pay more for a hunk of metal that you have to drill out and possibly mess up.

 

[Zach S]

MachIVshooter, I'm faced with too many time constraints to do billet. I'd be limited to my lunchbreaks, or long cycle times on my machine. Doing the profile on a billet, on a manual mill, would likely take longer than fabbing or machining a fixture for a raw forging.

To be honest, part of the appeal of the raw forging is the challenge, and if I totally screw it up, I'm out less money than I'd spend on a take of gas.

A magwell adapter is a no-go. The outside dimension of Thompson magazines are just as wide as the outside dimension as the lower, so the front section of the magwell would have to actually be cut off and replaced, similar to the Bazooka Bros lower that used M3 magazines, which was my inspiration.

Of course, making a new magwell and attaching it to the standard magwell using undercut flat head screws was also a thought.

I'll put more thought into it if the idea ever makes it out of my head and towards the vise. I'm assuming I'd need a feed ramp like the Colt 9mm, I know I'd have bolt modifications to do as well.

Thanks for your $.02.

 

[lysanderxiii]

If you plan the cuts right, you can do a billet in small digestible chunks that take less time than trying to set up an irregular shape like a raw forging.

As to the OP, 80% are a good learning project for introducing someone to machining, after making a bench block or machining a perfect 90 degree angled 1x1x1 cube from a chunk of steel with all six sides bandsawed out.

Then you can branch out, and make your own stuff.

 

[mljdeckard]

I would try it for the learning. (I know almost nothing about machining.) Just like I think reloading is part of the overall experience in understanding how stuff works. But as far as 'traceability' and cost go, no, I wouldn't bother. It's far too easy to get a paperless AR already.

 

[pintler]

Ray Brandes has a very good writeup on doing a raw forging. PDF's here:

http://arlower.ray-vin.com/ar15/

Chapter 1 has a drawing for a simple fixture that makes workholding pretty simple; see the bottom Chapter 1 for a pic and then drawings.

http://arlower.ray-vin.com/ar15/chapter01.pdf
http://arlower.ray-vin.com/ar15/drawings.pdf

You do have to figure out where to start so the finished part will be completely inside the forging. I didn't find that hard; I used a surface plate and a height gage to just do a trial layout of key fixtures. If your first eyeball guess doesn't work, reblue and guess again.

I was too cheap to buy a tap for the buffer tube threads, so I made a simple fixture to single point them on the lathe; basically a 2 inchish diameter bar with a flat cut so when the flat top of the lower is bolted to the flat, the buffer tube hole is on the lathe centerline.

He has a pretty clever way to do the magwell; sequences of milling cuts get you almost there and then you break out the file. I think it's elegant; see chapter 9. I had a shaper and so I used that instead, but his method is probably faster.

 

[MachIVshooter]

MachIVshooter, I'm faced with too many time constraints to do billet. I'd be limited to my lunchbreaks, or long cycle times on my machine. Doing the profile on a billet, on a manual mill, would likely take longer than fabbing or machining a fixture for a raw forging.

Making jigs and fixtures saves time for doing multiple runs, but is almost never worth the investment on a one-off.

It takes me about 20 hours to machine an aluminum receiver. My billet steel critter took 33. For perspective, I can knock out an 80% in about 30 minutes. 80% lowers are a lot more than 80% complete from a machining standpoint.

The problem with raw forgings (aggravation, really) is having to take so many extra steps to ensure that everything is square and that cuts are located properly relative to the already-formed exterior dimensions. With billet, you poke that front pin hole and then go to town, and you decide when to cut off the parts you left to make work holding easy. I complete most of the profile before separating the actual lower from the piece I squared up to easily chuck in the vise without having to indicate every single time, or worry about small contact points allowing movement during heavy cutting:

A magwell adapter is a no-go. The outside dimension of Thompson magazines are just as wide as the outside dimension as the lower,

Then a raw forging won't work, either. You're definitely looking at a billet critter.