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 No.214[View All]

Just wanted to post some preliminary progress regarding my AR18 build
i dont have any access to any examples of these because i live in a commie faggot state, but i've started to at least make progress on constructing an upper receiver flat.

im doing this with some knowledge ive deduced and some simplifications as such:
- an AR18 tubular receiver has internal dimensions of 1.25" x 1.25"
- an unbent flat will be approximately 5 inches across
- relative proportions from pictures will be close enough for function

using that i performed progressive rudimentary visual perspective correction for image 1 using GIMP and gridlines to get image 2. i then imported it into autocad and corrected for any rotation. i then visually mapped out the outline to get a general proportions. with this done i scaled the drawing to my 'known' dimension of 5 inches and examined the other dimensions. I then went through them and rounded up or down to units that are convenient to imperial system, and radiused select corners

This would be an iterative process of refining the flat given i dont even have access to an actual rifle. the only dimensions i can think of that will require being really close would be overall length and width. Width i know isn't going to be accurate, given that when bending sheet metal flat dimensions like that wont directly translate to the finished dimensions, but it think its a good starting point. length would be easy enough to change.

90 posts and 29 image replies omitted. Click reply to view.


ask your MAL friends to read it with you


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big progress– did the math to see if the positioning plate would work, numbers were close but it looked good
made it and did the bends
good results. ribs survived. fairly consistnet. actually bent it too tight on the second bend so its trapezoidal, but i can just break my tacks and adjust.
one weird thing is its actually lightly curved like a banana (maybe about 1/16" of an inch?). im still trying to figure out exactly how that happened
big step forward, though


>day skin

we need to talk about your 23andMe results


whats day skin?


notes for next attempts:
- prevent mid beam deflection by making a 1/8" steel flush pressure pad along with some flat head retaining screws
- make a section profile spacer plate to prevent overbend during second bending (in the future, combine this with the punch)
- adjust flange length for a perfect seam upon final bend (for fusion butt weld with TIG)

also adjust 1 & 2 for existing bent flat before moving on to next steps


some other stuff ive noticed
radius on the rib side is slightly crimped
tube is not square, especially on the front (its like a parallelagram). this likely happened because the bends happeed unevenly, and one side got overbent significantly
the guide rod base has a cutout at the bottom to accomodate overpen from the weld seam
i might have to increase the size tolerance for my tube to account for manufacturing defects


also after measurement, opening still isn't opened the same, in the middle inch, over .01" difference in width


yah we know you love increasing size tolerances for tubes


oh wow just wow




i opened it up a little more, but it still wasn't square (needs to open more)
i might go tonight and do that, i'll bring my calipers and actually measure one side to the other


ok i've got updates, will post later sunday


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Latest developments
I opened it up until square, actually significantly larger than I was expecting. Not sure if when I made the tooling I did that intentionally? But everything fits perfect, so doesn't matter either way. I just tacked it maybe 8 places evenly before machining
The issue with being out of square mostly disappeared, it turned out that only one side wasn't bent all the way on the front, and that was enough to throw it out of square when welded.once the pocket up front got machined it spring open on that side (that's why I have it clamped.
3d printed trunnion is in, guide rod and bolt carrier installed. Fits on the lower well but the fire control pocket is a little too small and it hits on the bolt hold open.
Gave a good lesson on work holding, glad I decided to take this one as far as I can, the 'production' one will be nice as a result.
Receiver is still slight banana shaped, but I think that will resolve by adding anything flat and rigid on top along with proper welding procedure
Next will be the cutouts for the bolt handle and holes for the cam pin rail


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oops sorry posted some image thumbnails on accident
also the camera/lighting did some weird shit, they look surprisingly decent considering i did all this on the fly
especially the last one with the clamp looking head on, the pic gives the illusion its not square, it is it looks p. clean IRL


looks great, can't be too far off now right?


nope its gettin real close.
still big hurdles ofc, but the bending stuff is the hardest and most involved.
the other stuff is just tedious machining (machining trunnion, machining front sight block, etc)
i'll 'finish' this one (i'll make simplified components with the critical features on it) so that when i do my next one, i'll have everything figured out and it'll be nice


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milled out the charging handle slot and the plug holes for when you weld the cam rail in.
noticing some unintentional differences with my stiffening ribs, namely the top one should be closer to the cutouts and a tad longer
can adjust on the final one.. kind of annoying though i'll have to mill a new female die
also fucked up milling the front of the charging handle slot, accidently grabbed an 11/16" with a 5/8" shank instead of a 5/8", so the front is 1/32 too big all around
really sucks, even though this is just the 'test' flat, it would have been nice to have a good looking one


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Slightly better one of the upper
My camera sucks


Can you reuse any of the material you goofed on?


I can reuse some of the tooling, if you mean this receiver nah not really but that's ok
I have a pretty good feel for what not to do, so chances for the next one to be near production quality will be good


Thats cool. Making mistakes is a corner stone of learning. Its pretty impressive what youre doing.


its been a really long time doing this project on and off
tonight, i will try to machine the trunnion


ugh nvm wont happen tonight
tomorrow, if im lucky


ok well i went sunday, almost got it done but accidently scrapped it
unfortunate but i know what to avoid next i suppose


What happened that made you have to scrap it?


so i did the press fit stuff perfect
when i was cutting the features on the bottom my endmill slipped in the collet and i lost some Z without realizing it
it was probly because its a pretty dull end mill, the collet may have been dirty too
anyway i broke through the press fit wall of the trunnion
also snapped the shit out of my 1/4" endmill on a plunge lel
i'll probly post a pic at some point


trying again tonight


FUCK this is gay
tire blew out on the way
so bad the mexican shop in the bad part of town wasn't even willing to patch it
gay gay gay gay gay


>not even the Mexicans will patch it


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got the trunnion made
went mostly ok, made a single mistake that resulted in damage to the front of it (not pictured) that was completely avoidable and I'm retarded
this one is good enough to test, tho


sir STOP lelling..


next time i go, i'll try to machine the barrel extension down and maybe press fit it
also will try to machine the front sight.
thats sort of a complicated on, but once its done thats the last major part
i have to make the cam pin rail too but thats dead simple


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>my phone sucks
yeah it does. Get a goolge pixel like everyone else in the world, fag



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Machined down the shoulder on the barrel extension and press fit it, no issues
Machined the cam pin rail
Welded aforemebtion two things onto receiver
Things are looking promising. Once I get the front sight done I can look at headspacing the barrel, making the rear sight, and test firing


so looks like might barrel extension is canted a degree or so, enough that 2 of the lugs have a very light interference with the bolt. Not sure if I should go through the effort of removing the extension or let it wear in


for further context, it does go into battery


did some troubleshooting with my friend looks like part of the issue was the rail wasn't perfectly aligned and was pressing hard on the cam pin, once the rail got moved things are pretty smooth now


Looking p good fam


thanks i'll post updates if i get some this weekend.. or earlier??!?!


its your world, post them whenever :D


ok so 1st attempt for the front sight
broke my 1/4" 2 flute end mill which i need to do most of the features– confirmed that my placement for the gas port was acceptable, depth of that stuff/thread depth was ok
but then when i tapped it i accidently tapped it an an angle, so its scrap now. i bought enough raw material to make one more, so i'll make a couple tweaks to the design to simplify it plus make a better sequence of cuts now that ive tried it once


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Machined a front sight. Had to leave off some of the more swoopy contours because it was just too complex. Fixture I made for doing the curves was finicky enough that I only used it for the large diameter around the barrel. Had one or two small mistakes but nothing that will affect function.
Once I headspace the barrel, I can drill the gas port and test fire.
oh I still have to make the rear sight though





whoa how many walmarts can you shoot up with that?


i guess that depends how much ammo you have


You have infinite ammo when you repack your used shells =D


thats too autistic even for me

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