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Musings- Homemade Sheetmetal AR Lower?

8K views 35 replies 13 participants last post by  allesennogwat 
#1 ·
May sound stupid, but I've been sitting here this morning trying to come up with a way in my mind that the average homebuilder could make a bent sheetmetal lower receiver that utilized standard AR components, and would mate up with a standard AR complete upper? Doesn't necessarily need to look like your standard milled lower mind you. Maybe like an AK style grip and trigger guard, weld on buffer tube mount, steel blocks welded or riveted in as structural members to hold the width, and to support the upper pivot pins, sheet metal magwell utilizing standard AR mag release. Seems doable in my mind, if not necessarily practical. One of those "do it because you can, not because you have to" kinda things. I think it would be an interesting experimental build. Kinda cool to make your own lower, and it not be like an 80% lower that you finished, but actually built completely.

Am I totally out in left field? Is there some critical piece of the engineering puzzle that I'm not thinking about, that's a show stopper? Not necessarily saying that I'm gonna build it, just trying to figure out if it's possible.

What say you, O great AR gurus?
 
#3 ·
Well that's good to know. Thanks Coils. I feel like less of an idiot now. LOL. Just seems like a fun sheetmetal build-it-yourself project. The more I think about it, the more I'm inclined to try it. Just because. I can't see it costing much more than $100.00 in materials, including a standard AR LPK. I very well may put this on the schedule for the summer, when it's too dang hot/humid to be out where I am.
 
#4 ·
yes its possible

Matter of fact it was done some years ago on home gunsmith forums, guy built blocks for the critical stuff(pivots and threaded tube for stock), welded it together and was functional, only thing he didnt do was the BHO, but thats a high precision area anyway
 
#5 ·
Did that a few years ago. It is a lot of work to be honest with you. Here is how I went about it....

1. I mocked the whole thing up using stiff cardboard. I should have used Kydex, but I really did not know it existed then. Once I had it the way I wanted it, I flattened out the cardboard and started cutting and drilling away. BIG MISTAKE, only cut, do not drill....Restart.

2. I made the lower in two parts: Trigger housing, and magwell, and used a steel bar to mate them, and house the BHO.

3. I used standard pins and cut a slot into each end to accept a c-clip, since the pins are longer than needed (because the trigger housing is only .064 thick) it worked out really well.

4. I made a Frankenstein looking buffer tube / rear trunnion / ugly spud that was spot welded to the trigger housing. This is what the rear pivot pin goes through. Now, think about those stupid little pins and springs that keep the pivot pins from falling out...Yup, the rear trunnion has those, along with the selector - keeper. This rear trunnion was the hardest bit of the whole project. It extended into the trigger housing all the way to the trigger group. It was good though because when I spot welded it into the trigger housing, I can guarantee that it was going NOWHERE....

5. The BHO / mating bar was spot welded to the front of the trigger housing, and then the mag well was spot welded to it as well. The mag well overlapped the trigger housing, and was cut out to allow me to mount the BHO pivot. In hindsight, I would simply have added a tab to the front of the trigger housing that would be bent out as the rear of the BHO pivot, and did the same to the mag well to form the front of the BHO pivot. It would have been simpler...

6. Now for the fun parts.....The front pivot pin went through another block that was spot welded to the front of the mag well, and the stupid little pin that holds it in was drilled from the top....Looked really funny, but it worked. A pressed steel flat was made for the BHO pivot. I used a modified L1A1 pistol grip and a loose nut to attach it. I also used an L1A1 trigger guard as an afterthought.

That was phase 1 of my infamous "Freedom Rifle" concept. It was heavy, and it was ugly. I truly shed tears when I destroyed it.

The good news is that it worked, flawlessly, which was a miracle in itself.

I revisited the concept again a couple of years later, this time I was out to make my own version of the AR-180 that would use as many AR-15 parts as possible. That worked too.

Both projects were fun. Both were successful. I never did anything with either idea because it costs more in tools and time than just buying an 80% completed lower.

However, for someone like yourself who already has the ability to press a receiver from a flat, has access to a spot welder, has the ability to install rivets, this is a really fun and rewarding project. All of the measurements that you need are available if you have an AR lower.

Let me know how this goes...

Regards,
 
#6 ·
#7 ·
Bellson, you don't have any pics to go with your description do you? That sounds like it was a fun project, and I'm inspired knowing that it workd once all was said and done. That is too cool. I think I AM gonna try this. It won't be until later this year after I finish up a few other projects. I think it will be an interesting build, that truly shouldn't cost much in materials. Just lots of labor, which is perfect for me. (Gotta keep busy when I get home from work, or else I'd just sit in front of the TV and turn into a zombie.) I really appreciate you posting that. Very inspirational. Thanks!!!!

Rocster, that is some crazy sh*t!!!!!!! Lower made from a kitchen cutting board!!!! Hell, I thought I was nuts thinking about bent sheetmetal.

Thanks for the input KZ, and all of you guys. It's definitely going on the "must build" list.

BTW, I do have an M4 that I can get all of my dimensions from, as well as most of the raw material. Might even have a few AR parts left over to help. This is gonna be fun!!!!
 
#19 ·
Hi 2nd,

Sadly, no pics.. This was in the heyday of the Kalifornia "Zip-Gun" enforcement...Kalifornia decided at one point in 1997 to crack down on home-builders by declaring the arms as "Zip-Guns". It failed due to supremacy, and because the firearms were patterned after "Real" guns as opposed to plumbing pipe .410 shotguns, etc. But I was VERY careful just the same.

The hardest part was the rear trunnion. I ended up making it out of steel, but it could have been done out of aluminum as well. I tried it, but my design was a bit too fragile for riveting. If I would have just designed it and treated it like an AK rear trunnion, it probably would have worked.

I think that we (all of us) should collaborate on this idea openly, and try to get to a workable design that can be home built. I agree, the costs would be next to nothing for the materials. If we could get one of us to bend up blanks for $15, and another to machine simple trunnions and center bars for $15, I think that complete lowers could be built for less than $60. Not much room for profit in there, but as a collaborative project and a stick our collective finger in Obammies' eye, it would be worth it.

Regards,
 
#9 ·
Cool, thanks Jimmy.
 
#10 ·
yea i saw one not all that long ago.

i have considered the wooden lower --might work if it had some steel here and there.

the alternate AR might be a bit less problematical if it was designed with non-standard lower and FCG parts.

when i was thinking of doing a sheet metal --i was planning on going with AK style FCG parts-- it can certainly be done and made to work--
 
#11 ·
That's what I was thinking 427. Maybe a hybrid FCG between AR/AK. I was trying to think about the wings on the AK hammer that the trigger hooks onto. It would be simple if there was enough width in the AR bolt carrier slot for the AK hammer to swing through it's full arc and hit the firing pin, but I don't think it's wide enough. Of course I'm at work without the parts in front of me to measure. Maybe use a PSL style hammer with the single wing, and offset the trigger just a little so that there is room for the one left wing to arc up through the carrier slot?
 
#14 ·
Thanks Gunny, but it won't let me search without being a registered member. Can you provide a direct link to the thread? TIA,
 
#16 ·
Well, I guess I'll just have to join another gun board. LOL. I just hate joining some of them to go look at one thing, never to return.

By the way, I love your signature!! Ron Paul for President!!!!!!!!!!!


Update: They require $10.00 to join. Sorry, I understand they need operating capital, and am not knocking them in any way, but I'm not paying just so I can go look at something I may or may not use in "my" build. Oh well. Thanks for trying Gunny.
 
#17 ·
Bellson, I found your old thread on the Freedom Rifle, titled "A new rifle design", and have been reading it. Its an awesome thread so far. I plan to do some more research on it. Thanks!!!

Coils, I have always known the name AR180, but had no clue what it was. Never seen one. Looked it up on Wikipedia, and that was a good read. If the AK platform hadn't already been ingrained into the 3rd World culture by then, a stamped sheetmetal receiver rifle similar the the M16 probably could have taken off. Thanks for pointing that one out. I feel extremely ignorant when it comes to unusual or non mainstream firearms.
 
#20 ·
I definitely like the idea of a collaboration Bellson. Get several of the regulars involved in engineering and manufacture of individual components.

First step if we want it to be a semi-production "kit" is to get one of our fine CAD operator type persons like Smartbomb to start putting together a file that we can work on to finalize dimensions, etc....

I am really looking forward to this project. Something new and interesting. Thanks for your help Bellson.
 
#22 ·
Coils, I have always known the name AR180, but had no clue what it was.
The first time I seen one of the older models was about three years ago at a local shop, had no idea what it was and came home to check it out online, went back the next day to put it on lay-a-way and it was sold. :( Been looking for one at a good price ever since, most in this area are in the 1300-1500 range.
 
#23 ·
#25 ·
yes there was a build on home gunbuilds( roderus) using sheet metal plates,

further back that that, just when the first building sites started on the internet, there was two interesting sheet metal builds. each concept/ build was taken from the WW2 M-1 carbine lower builds, seem near the end of WW2 one contractor figured they could take sheet metal sheets and braze them together, then cut out the lower. This is a fact because, I own one of these lowers!

anyway on to recent history, these two guys did the same thing using that same concept, one brazed his sheets together and attached a buffer tube feature to the end, the other guy used screws to attach his sheets. they both worked fine, not perfect but functioned

amazing what you can do if you use your head
oh there was also a few done with AK builds, and one that was assembled like a erector set built kit (if your over 45yrs old you will know what that is)

history lesson for today is over

sprat
 
#26 ·
Cool, thanks for the info Sprat.

And unfortunately I know what an Erector Set is, and did own a set. As well as a Lincoln Log set. LOL. I'm really feeling old, thanks!! Of course it doesn't help that my son turns 27 next week!!!!!
 
#27 ·
The sheet metal build on homegunsmith.com was done by agreyman. Google might be able to search for the threads for you.

I've also seen the one from cutting boards, and there was another one a guy made out of a pine board. It was incredibly ugly, but it worked.

What you have to keep in mind is that the AR's upper contains all the important bits, and recoil is transferred straight back to the stock from the upper. The lower is just a bracket to hold the trigger group and magazine.
That's why, although it was designed as a 7075 aluminum forging, at least one company injection molds them out of plastic.
 
#30 ·
Got it Gunny. Thanks!!!!! A tremendous build brother!! That thing looks WAY nicer than I was thinking of, but has now set the bar for me. It definitely gave me plenty of ideas. You don't happen to have any plans on the jigs that you used, or want to get rid of the jigs, do you?? Hope you don't mind an e-mail or three questioning various things.
 
#31 ·
Jogged my memory yah I was a member and a contributing member at roderus homebuilders before the payment was required nonsense

yep Greymans build it was

TRX is right about the plastic, wood & etc lowers, but I keep reading threads about using the old tannery/other makes of cast lowers, claiming to be not satisfactory, on that note my tannery lowers have held up

sprat
 
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