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/h/ - Hobby Autism

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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.

133 posts and 46 image replies omitted. Click reply to view.


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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


ok the latest:
>tool came in for holding the barrel extension by the lugs
>did preload calcs for the barrel/extension
>did some geometric checks to see if my chamber depth was deep enough to be safe
>figuring out how i'm going to headspace/how im going measure the gap i need for my spacer
that second to last one was kinda interesting
to elaborate a bit, theres a couple different ways that headspace is typically done. the most conservative way would be to make the bore as deep as possible, then adjust from their to get proper headspace. that way the maximum extent of the cartridge is supported
i had no idea what if anything was done with this barrel, because i bought it from some guy outside a UPS warehouse and it has no markings. its pretty weird for these things not to have an extension on it already too.
so what i did was measured how far the gauge sticks out when fully seated, then looked at the internal geometry of the case to see how much needs to be supported to not explode. then some simple geometry to make sure the cartridge is adequately supported throughout the entire safe range of headspace
i need to modify the barrel extension tool to fit inside the receiver, then make essentially a crowfoot to fit split clamp that ive got on the barrel so i can torque it to the range i need. since the shoulder on the barrel is further up than the proper headspace range, i'll need to machine a spacer to fill the gap. that spacer needs to be the proper size so that after im done torquing to the number i determined, the barrel will be in the safe headspace range


i made the crowfoot, the machining went great came out beautiful, then the welding went mostly ok except one of my welds looked a little ugly so i was going to do a pass over with teh tig torch but i forgot to turn the shielding gas on and it did fucking NASTY stuff
spent like 2 hours trying to clean the weld up to something that didn't look like disgusting
also i added a relief cut to the barrel extension tool, so it fits now (it didn't fit before).
that was a obnoxious


It's crazy to think you've taken all this time and precision creating this, and there's probably kids stamping parts in my huts in Africa and South East Asia for the same reason. Really makes you wonder.


>probably kids stamping parts in my huts in Africa and South East Asia for the same reason
wait if they're your huts why wouldn't you know if they're stamping parts or not?
and why do you have huts in africa and south east asia??




Mud huts*


>forgot to turn the shield gas on
damn man did you go full retard and shit it up entirely or just zapped it real quick and realized you fucked up?


i went full retard for like a full few seconds wondering why this thing was popping and bubbling all over the place
it turned out fine tho, grind it down, went back over it. a bit of porosity but double sided fillet was overkill anyway
headspacing went super smooth. very easy, i've got a good system now. cheap too


designing a rear sight
hope to make the rear sight wings this weekend


you should prolly still double check it after the first time firing it but you know what youre doing good luck


i'll be extensively checking brass, primarily


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Well it looks like a gun now
3d printing a stand in rear sight now. Have a bit of cleanup to do on the rear sight since I made it by hand
Will finish welding next time. Rear sight wing holes didn't line up, so will need to plug a side and redrill.
Did some other stuff too including some fuckups, I'll write those up later


Looking good my guy


ur lookin good bby 😎


did some naaaasty welding on the rear wings, contouring them to look nice with the dremel
i dont really care tbh im gonna hammertone rattle can this bitch to hide most flaws anyway
debating whether i'll even parkerize it


got a lot of cosmetic flaws cleaned up this week (lots of welding, grinding, filing)
i didn't want to do any of that but i just can't fucking help myself
i still have a couple spots i need to weld (finish the seam on the receiver) but then thats it
then i'll sandblast it (probly with playsand like ive done before), then wash it, parkerize it, prime the exterior, then hammertone paint.
oh also still have to clean up the front sight block, drill the gas port etc
gettin pretty close tho, most of the major construction is done


another 6ish hours of grinding/sanding
i've got most of the weird cosmetic flaws feathered into the good stuff
i have a lot of experience doing dremel magic after i did the CETME a few years back
being a lot less careful this time though since its going to get a thick hammertone paintjob which will hide even big fuckups
i also split the difference for the charging handle opening where i drill the hole 1/16 too big, i enlarged 1/32 both sides and blended it over the full 4-5 inches
hides pretty well. looks decent
action is feeling very smooth. with the dog leg charging handle i can still induce a malfunction if i push or pull down on at, but i think im ok with that. shouldn't happen during firing, and this is just a prototype so im willing to make compromises. i really dont want to have to push this thing out and repress fit it at the right orientation, although that would be the proper action.


nothing is worse than a malfunctioning dog leg charging handle…


whats wrong with the charging handle does it keep barking at you?


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so with a regular charging handle, the handle itself isn't very long.
the dog leg one comes out about 2-3 times as far, and is also offset way above, pic related.
the result is its pretty easy to torque the guide rods pretty hard. easy enough to rotate the entire bolt carrier a couple degrees
well my locking legs are already sllightly canted because i didn't press the barrel extension perfectly aligned, so pulling down on the charging handle can induce a malfunction where the bolt lugs can't rotate far enough to unlock fully


better post vids of testin


how bad does it get stuck if you do that? like you gotta kick the shit to loosen it or just smack it a little?


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as in 100% stuck while in the induced position
kaki for illustration. in normal conditions, theres enough clearance for the bolt to clear the lugs. when charged at the wrong angle, with the dog leg charging handle, its possible to rotate the entire bolt carrier/guide rods/ bolt enough to suck up that clearance and prevent fully unlocking
if it were to get fired in that position may well tear off a portion of the lugs during unlocking. it wouldn't be dangerouse unless unnoticed and i were to keep firing
will post another pic in a second showing a bolt and lugs in case you're not familiar


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heres an ar15 cutaway gif which has an essentially identical locking system


finished my welding, went really well. got my settings figured out on my welder finally. used a big piece of aluminum as backing. easy and clean
then spent 3 hours trying to get my siphon blaster to work. compressor is way too tiny, too much moisture in the air. won't pull. nozzle worn out. not enough siphon effect


woah that thang can kinda kill nigrs


ok i'll post progress pictures today
last night i drilled the gas port, dimpled the barrel for a set screw, and threaded the front sight (for said set screw)
i wanted to sand blast but im having a hell of a time getting my siphon blaster to work.. i think my air is too wet. what a pain…


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Handguard length exceeded the dimensions of barrel journal and handguard retaining ring (about 1/16).

Likely reason is that trunnion is longer than actual. Handguards and retaining ring were shaved down the required length at front for gas block to position properly.

Trunnion was not installed straight. Misaligned by about 1/8 over 12 inches. Makes front sight block appear canted. Seems to be within workable tolerance of the piston system.


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Fuck other pics didn't post.
Shown are the gas port, fitup of the retaining ring/front sight/handguards


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quick video showing assembly and getting a few angles on it

if you saw the blem above the gas port with the tap wrench pic, tis because my edge finder jumped the edge and gouged the journal. wild what machine tools can do


lookin great budy. do you have to make custom mags for it too or is it compatible with factory shit?


they take stock AR mags
even the original AR18 took slightly modified AR mags
so im set


Does it fire 5.56?


it does


can't wait for a video of it shooting at thangs


give me directions to Ironton, Ohio


thread protector came in, looks kinda gay but wtver i can't put a flash hider on it here legally
also decided to get my handguard 3d printed because its fucking cool for me to have designed all the furniture, the website is broken and accepts expired coupons that are supposed to be way more expensive shit, and i wanna see how closely i was able to reverse engineer them. they should arrive next week sometime
also need to make a new rear sight and system for how the rear sight adjusts, last set didn't work


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nice, handguards should be here wednesday
hope they fit


I would've invested in a sneeze guard instead


w-ww-w-w-ww-ww-w-w—ww-w-w-whatdo you mean????!??!?!??? .. ?1


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Got the heat shield flats cut out
After I do the bends I'll cut out the remaining material
Then I'll clean up any ugly eges and sandblast it with the rest of the stuff to give it a dull finish


Bout ready to brougleigh them niggas huh?


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ok nerd lmaoo

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[ 76 / egy / h / kc / librejp / sp / v ] [ ukko ]