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shalafi4
Feb 20, 2011

another medical bills avatar

DJExile posted:

I don't have a lot to add but this is genuinely one of the best threads I've seen in years and I'm really interested to see how it all comes out.

Even if you don't think you have much to add feel free to join in when I ask questions! Everyone might learn something from it!

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The Eyes Have It
Feb 9, 2008

Third Eye Sees All
...snookums

This is really neato. It's also interesting to peek at the design process for metal work. I have zero metalworking experience (except for a welding class that was ) in myself or friends or relations so it's neat to see the design process insides which are so different from my usual "head straight to the workbench for a quick proof of concept" that I do with electronics.

Basically high tech really complicated legos is what I'm kinda used to as a step 1, followed by serious CAD stuff only later, especially for production.

shalafi4
Feb 20, 2011

another medical bills avatar

Mister Sinewave posted:

This is really neato. It's also interesting to peek at the design process for metal work. I have zero metalworking experience (except for a welding class that was ) in myself or friends or relations so it's neat to see the design process insides which are so different from my usual "head straight to the workbench for a quick proof of concept" that I do with electronics.

Basically high tech really complicated legos is what I'm kinda used to as a step 1, followed by serious CAD stuff only later, especially for production.

Completely understand. The electronics deity that has the office beside me said something pretty similar a few weeks ago.


Also

Arse Porn Cage
Oct 9, 2003



You may want to trade notes with BFG Cartridges. They even call their .358 Gremlin the 9x39 USA. Their cartridge is meant to be legal for deer hunting in Indiana rather than for suppressed shooting, and I'm not sure how close the dimensions are for the two rounds. Also, they only offer their cartridge in bolt-action rifles, so if you get an AK to cooperate with yours, you'll be way ahead of what they've been able to do. I only know of the Gremlin from seeing it in Cartridges of the World.

Javid
Oct 21, 2004

My sole partiality is to that delectable spiced meat. Any additional confederation of vegetables shall not compromise the pie as I see it.

I was wondering about the availability of 358 bullets vs. 366 but apparently 9.3mm is a big huge thing I'd never heard of until looking for it so there's plenty of options.

Any chance you'd care to crank out some dummy rounds for the collectors among us?

shalafi4
Feb 20, 2011

another medical bills avatar

Arse Porn Cage posted:

You may want to trade notes with BFG Cartridges. They even call their .358 Gremlin the 9x39 USA. Their cartridge is meant to be legal for deer hunting in Indiana rather than for suppressed shooting, and I'm not sure how close the dimensions are for the two rounds. Also, they only offer their cartridge in bolt-action rifles, so if you get an AK to cooperate with yours, you'll be way ahead of what they've been able to do. I only know of the Gremlin from seeing it in Cartridges of the World.

This is going off of memory.
The dimensions are pretty close? The 358 Gremlin if I remember correctly is simply a necked up 7.62x39 and the shoulder angle is modified. The 9x39 has the case body angle changed much straighter as well.

The 358 gremlin guys also are going for a completely different goal. They are making (comparatively) high velocity hunting rounds where as we're going the subsonic route.

That being said the cases are close enough that it would work perfectly fine in the AK we're building.


I should see if it's in my giant book of reamer tech drawings. I could see a lot more definitively on the differences.


Javid posted:

I was wondering about the availability of 358 bullets vs. 366 but apparently 9.3mm is a big huge thing I'd never heard of until looking for it so there's plenty of options.

Any chance you'd care to crank out some dummy rounds for the collectors among us?

yea the 9.3's are common in Europe but never really took off here in the US. (45-70 supremacy)


And I can defiantly make some dummy rounds

I can make some now although they have a tiny wasp waist to them since I haven't made an expander that fits the case web profile yet.

Kthulhu5000
Jul 25, 2006

by R. Guyovich


Kind of a "drr" question, I guess, but any idea how this sort of cartridge would fare in a full-auto gun? More recoil, more stresses to contain, etcetera?

shalafi4
Feb 20, 2011

another medical bills avatar

Kthulhu5000 posted:

Kind of a "drr" question, I guess, but any idea how this sort of cartridge would fare in a full-auto gun? More recoil, more stresses to contain, etcetera?

It should do fine in a full auto. Most if not all of the actual Russian military rifles chambered in it are capable of full auto fire.

*educated guess time*
It probably has a bit more felt recoil? The stresses on the bolt/recoiling assembly *should* be pretty comparable to a normal AK 47 so that shouldn't be an issue.

fundamentally it's an AK47 that's chucking about 2 1/2 bullets worth of weight out at a lot lower velocity.

OWLS!
Sep 17, 2009

by LITERALLY AN ADMIN


5'd, subbed, bricks dumped, heavy breathing in anticipation.

Gorgonzola Cheese
Feb 20, 2007
Gorgonzola's revenge!

Question!
I thought the gas set up on AKs was a poor choice for suppressed rifles - How will you get around that?

I think I read that somewhere, maybe I made it up.

Don't be too hard on me

Gorgonzola Cheese fucked around with this message at 05:18 on Dec 3, 2015

shalafi4
Feb 20, 2011

another medical bills avatar

Gorgonzola Cheese posted:

Question!
I thought the gas set up on AKs was a poor choice for suppressed rifles - How will you get around that?

I think I read that somewhere, maybe I made it up.

Don't be too hard on me

At least from what I've read about it's kind of a yes and no at the same time on whether they are or not.

The biggest "issue" that people seem to complain about are the blow down ports directly behind the gas block.



on the left image at the top you can see some small holes around where the gas piston would sit.

apparently those have people complaining that they make noise and spit excessive amounts of gas out when suppressed. I don't have any direct experience with a suppressed AK so I can't say for sure much past that.

(personally the amount of gas barfed into your face from a suppressed AR with a badly fitting charging handle is probably worse... that I DO have experience with)


One thought that I did have and I'm not sure on if we would do it or not is to have the blowdown ports on the actual gas tube its self and maybe have a sliding sleeve that could cover them. I don't have all of the gas port specifics ironed out as of yet.


If anyone has any experience with one please feel free to chime in.

shalafi4 fucked around with this message at 05:33 on Dec 3, 2015

right arm
Oct 29, 2011



those people have no idea what they're talking about. my 550 and R4 both vent similarly and are every bit as quiet as my AR15 with no blowback

shalafi4
Feb 20, 2011

another medical bills avatar

So I figured I would try to get into the late 90's and make a thing


shalafi4
Feb 20, 2011

another medical bills avatar

Alright.

Last time we figured out our barrel dimensions and were ready to continue designing the front end parts.

To recap we have a trunnion end diameter of 0.917 and we figured out a barrel diameter of 0.866 would work fine.


Now to tie up the other constraints.

Center line distance between the gas piston and the bore.

Diameter of the gas block socket.

Length of the gas piston



Ok... length of the gas piston we'll deal with when we attach the gas block to the barrel. It's a pretty simple matter of lock the bolt&bolt carrier into the trunion. Measure to the proper length and mark appropriately.


one down.

The diameter of the gas block socket (I couldn't come up with a better name for it)



For this I just did a direct measurement of both of the existing gas blocks from the parts kits. Which came out to about 0.650" (oddly round number for something designed in metric) You'll also notice a pretty heavy taper leading into the socket. I took a little creative license with this. It is close to the normal dimension but it is tweeked a tiny bit deeper than normal.


The center line distance I also took direct measurements off of. (unfortunately I don't have a photo of the setup... someone bug me to take another photo of the setup later)

Picture two precision pins socketed into the holes in the gas block.
I know the dimensions of both of the pins.
Measure the outer dimension of the pins.
Subtract the radii of each pin.
Volia center line distance


With that out of the way I got the gas block mocked up and all of the detail work done.

With that however for our front and rear sight block we have another constraint that we didn't have before.
The tops of the sight blocks need to clear the gas block.


It also brought up another question. How are we going to attach sights to this?

I was pondering for the better part of a week on how I was going to retrofit AK sights onto the project. Cut and weld? machine new ones? cannibalize some parts but not others?


Myself and the other guy in the project were talking about it and after probably close to 2 hours of debating and contemplating my friend asks.

"Why don't we just put a front and rear rail on it like an AR? "









BRILLIANT!!!


After some tinkering with solidworks

Meet Front block



And Rear block




And after looking up the specs for mil spec rails the whole family is done.




bonus points to the person who figures out what feature is missing on the rear block. (other than pin holes)

Roundboy
Oct 21, 2008


shalafi4 posted:


bonus points to the person who figures out what feature is missing on the rear block. (other than pin holes)

Don't you need to have some method to lock in / remove the gas tube ?

shalafi4
Feb 20, 2011

another medical bills avatar

Roundboy posted:

Don't you need to have some method to lock in / remove the gas tube ?


That wasn't the one I was thinking of but that is absent on the drawings.


Due to something I was planning on talking about in the next installment we're actually welding the gas tube in place. All of the front end blocks are going to be Stainless. (the rails are something else however)

Shaocaholica
Oct 29, 2002

Fig. 5E


Any reason why you didn't just merge the gas block and front sight mount into a single part?

shalafi4
Feb 20, 2011

another medical bills avatar

Shaocaholica posted:

Any reason why you didn't just merge the gas block and front sight mount into a single part?

It would only give something like an 8" sight radius




we thought about it but figured might as well make proper front sights for it in case we want it.

Shaocaholica
Oct 29, 2002

Fig. 5E


Ahh. Well do the combo block anyway for the SBR version


Also, what do you think will happen if you chamber and drop the hammer on a 7.62x39? From a accident/safety perspective?

Javid
Oct 21, 2004

My sole partiality is to that delectable spiced meat. Any additional confederation of vegetables shall not compromise the pie as I see it.

Shaocaholica posted:

Also, what do you think will happen if you chamber and drop the hammer on a 7.62x39? From a accident/safety perspective?

My guess is that if it even goes off, it will look something like this:



The bullet will fart out in a relatively safe manner, the case will then be fireformed, and the action probably won't cycle.

That's if it goes off. I'm not sure if the shoulder is close enough for it to headspace correctly; if it doesn't the firing pin probably won't even get a proper whack at the primer.

shalafi4
Feb 20, 2011

another medical bills avatar

Javid posted:

My guess is that if it even goes off, it will look something like this:



The bullet will fart out in a relatively safe manner, the case will then be fireformed, and the action probably won't cycle.

That's if it goes off. I'm not sure if the shoulder is close enough for it to headspace correctly; if it doesn't the firing pin probably won't even get a proper whack at the primer.

It would *probably* go off since the section right in front of the case head is the same dimensions as a 7.62x39.

However I doubt it would actually fireform like that. The case would probably rupture down most of its length and the bullet would probably ooze out of the barrel since the bore is significantly larger.


Closest comparison I can think of would be drop a .357 sig into a 10mm chamber. Some flash, some noise and a lot of WTF just happened

Shaocaholica
Oct 29, 2002

Fig. 5E


Would that kind of discharge damage the ID of the barrel?

shalafi4
Feb 20, 2011

another medical bills avatar

Shaocaholica posted:

Would that kind of discharge damage the ID of the barrel?

If you did it all the time? probably.

once or twice? I doubt it.

Lathespin.gif
May 19, 2005


Pillbug

Just wanted to say I've been waiting for this thread to pop up for ages, hell yes this is the Good poo poo

shalafi4
Feb 20, 2011

another medical bills avatar

Lathespin.gif posted:

Just wanted to say I've been waiting for this thread to pop up for ages, hell yes this is the Good poo poo

If you have any input on setups/what to show everyone feel free to chime in.

shalafi4
Feb 20, 2011

another medical bills avatar

Ahhh the smell of burning coolant in the morning

Shaocaholica
Oct 29, 2002

Fig. 5E


Do you have to make a bunch of additional cuts so that your new parts play nice with furniture?

The Eyes Have It
Feb 9, 2008

Third Eye Sees All
...snookums

How long does something like that take to cut? And how much baby sitting (watching carefully, swapping bits, etc)

I think the answer is somewhere between "more than I'd think" and "less than I'd fear"

shalafi4
Feb 20, 2011

another medical bills avatar

Shaocaholica posted:

Do you have to make a bunch of additional cuts so that your new parts play nice with furniture?

just a few.... dozen... yea....

Here's a repost of the .gif that has the tool paths for the front sight block. The other parts have similar paths.






Mister Sinewave posted:

How long does something like that take to cut? And how much baby sitting (watching carefully, swapping bits, etc)

I think the answer is somewhere between "more than I'd think" and "less than I'd fear"

Actual cutting time on that one was only around 12 minutes?

The first one takes significantly longer because I babysit it from start to finish to watch for any coding fuckups. After that once the part is set correctly press play and walk away (it's only one tool)

that being said ALL of the operations in the gif (on the computer side) says it's going to take an hour and 58 minutes @ 100% feed and that's just cutting time not counting the changes between the 5 other tools and re orientating the part.

shalafi4 fucked around with this message at 22:04 on Dec 11, 2015

Herr Tog
Jun 18, 2011



Grimey Drawer

Keep at this it is fascinating

shalafi4
Feb 20, 2011

another medical bills avatar

Have some machining Pr0n to hold yourself over until I get the time to write the next full update

This


Plus this


Equals this



Also click to biggify and you can see the tool paths in the block.

Diabeesting
Apr 29, 2006

turn right to escape

Hnnnngggg I can't wait to see the finished product. Have you mocked up what the full rifle might look like, with furniture and everything? Or is it too early to tell what will and won't work out

shalafi4
Feb 20, 2011

another medical bills avatar

Munnin The Crab posted:

Hnnnngggg I can't wait to see the finished product. Have you mocked up what the full rifle might look like, with furniture and everything? Or is it too early to tell what will and won't work out

It'll look like a goofy AK with rails for the rear and front sights. We're not trying to reinvent the wheel, just make less drag

Doctor Grape Ape
Aug 26, 2005

Dammit Doc, I just bought this for you 3 months ago. Try and keep it around for a bit longer this time.


shalafi4 posted:

Have some machining Pr0n to hold yourself over until I get the time to write the next full update

This


Plus this


Equals this



Also click to biggify and you can see the tool paths in the block.

I always wondered how weird profiles like that got machined, neat! Would something like this be possible without CNC?

MohawkSatan
Dec 20, 2008

by Cyrano4747


Doctor Grape Ape posted:

I always wondered how weird profiles like that got machined, neat! Would something like this be possible without CNC?

It'd be readily possible without CNC, but it'd probably take a whole gently caress of a lot longer. I've got a somewhat related question: How many bloody passes is that, and what kind of tool were you using? Looks like it was just a small endmill, and a fuckload of passes. Also, are those 3/4" drill parallels? Why not use actual milling parallels? Would the extra width get in the way of something? How long did it take to program the procedure and finish the cutting on the part?

shalafi4
Feb 20, 2011

another medical bills avatar

Doctor Grape Ape posted:

I always wondered how weird profiles like that got machined, neat! Would something like this be possible without CNC?

oh it defiantly could be done without CNC. IF I start making a bunch of these and I still don't have CNC access I'd probably rough cast them and machine the critical surfaces.

MohawkSatan posted:

It'd be readily possible without CNC, but it'd probably take a whole gently caress of a lot longer. I've got a somewhat related question: How many bloody passes is that, and what kind of tool were you using? Looks like it was just a small endmill, and a fuckload of passes. Also, are those 3/4" drill parallels? Why not use actual milling parallels? Would the extra width get in the way of something? How long did it take to program the procedure and finish the cutting on the part?

# of passes? ummmm yes

tool used

0.250" dia 5 flute 0.015" radius bullnose endmill

Parallels:
They're 1/8" thick parallels. Typically I use 1/32" thick ones but I was lazy.

The wider ones would be fine for the application but the majority of the projects in the shop are smaller/are ran by students. If we had wider parallels they would wind up with holes in them.


Programming wise I think I have about 45 minutes in plotting the CAMM for the entire part (not just this face) The total run time once I tweeked the speeds some was about 55 minutes (most of which is the fluff detail finishing)

shalafi4
Feb 20, 2011

another medical bills avatar

Remember kids, no friction welding in the machine shop.


Doctor Grape Ape
Aug 26, 2005

Dammit Doc, I just bought this for you 3 months ago. Try and keep it around for a bit longer this time.


shalafi4 posted:

Remember kids, no friction welding in the machine shop.




No matter what a stripper says?

shalafi4
Feb 20, 2011

another medical bills avatar

Doctor Grape Ape posted:

No matter what a stripper says?

I don't wanna know how much chafing it takes to friction weld.


Press fits however are encouraged.

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The Eyes Have It
Feb 9, 2008

Third Eye Sees All
...snookums

What exactly am I looking at there? I think it's maybe an "obviously" dulled or broken cutting bit but I am super uneducated about this stuff.

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