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Posted: 2/22/2019 11:13:38 PM EDT
[#1]
I would not even attempt to put a round through it, all of the pressure is in the upper receiver and barrel, sounds like a great recipe for a nice kaboom.
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Posted: 2/22/2019 11:47:57 PM EDT
[#2]
Quote HistoryQuoted:
I would not even attempt to put a round through it, all of the pressure is in the upper receiver and barrel, sounds like a great recipe for a nice kaboom. 
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Posted: 2/23/2019 12:10:27 AM EDT
[#3]
Quote HistoryQuoted:
you mean plastic won't contain a 35,000 psi explosion? 
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Posted: 2/23/2019 12:42:30 AM EDT
[#4]
Quote HistoryQuoted:
you mean plastic won't contain a 35,000 psi explosion? OP, as long as its properly in battery, I don't doubt it will fire once. From what I understand PLA is very soft and low-temp. I would try to find someone who can at least print it in Nylon, that stands a better chance of lasting more than one round. The main issue I see is that the weight of the barrel, and the resultant torque from the tip whipping up and down after firing would likely crack the threaded portion off. That or the lugs the takedown pins go through would break or deform severely. |
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Posted: 2/23/2019 12:55:17 AM EDT
[#5]
Quote HistoryQuoted:
you mean plastic won't contain a 35,000 psi explosion? Quote HistoryQuoted:
Quoted:
I would not even attempt to put a round through it, all of the pressure is in the upper receiver and barrel, sounds like a great recipe for a nice kaboom. |
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Posted: 2/23/2019 12:59:37 AM EDT
[#6]
SLA materials are nice, pretty, clean and brittle.
They are good for fitment parts and to show parts at trade shows and such. They are not enfgineering grade materials. I wouldn’t ever try an SLA part for function testing an upper. Maybe DMLS but that would take a lost of secondary operations to smooth out the internal features of the upper. This is what I do for work and have had people ask the same question. |
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Posted: 2/23/2019 1:01:41 AM EDT
[#7]
Quote HistoryQuoted: It...doesn't have to? I would hope the barrel, barrel extension, and the lugs and bolt are containing the pressure and not the receiver. The receiver just ensures the stability of components and guides the bolt carrier. You think the aluminum of the upper is any stronger than the steel it holds together? You all forget that Bushmaster made a glass-filled nylon upper receiver once. Not terribly durable but it wasn't a bomb. OP, as long as its properly in battery, I don't doubt it will fire once. From what I understand PLA is very soft and low-temp. I would try to find someone who can at least print it in Nylon, that stands a better chance of lasting more than one round. The main issue I see is that the weight of the barrel, and the resultant torque from the tip whipping up and down after firing would likely crack the threaded portion off. That or the lugs the takedown pins go through would break or deform severely. |
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Posted: 2/23/2019 1:02:38 AM EDT
[#8]
Quote HistoryQuoted: It...doesn't have to? I would hope the barrel, barrel extension, and the lugs and bolt are containing the pressure and not the receiver. The receiver just ensures the stability of components and guides the bolt carrier. You think the aluminum of the upper is any stronger than the steel it holds together? You all forget that Bushmaster made a glass-filled nylon upper receiver once. Not terribly durable but it wasn't a bomb. OP, as long as its properly in battery, I don't doubt it will fire once. From what I understand PLA is very soft and low-temp. I would try to find someone who can at least print it in Nylon, that stands a better chance of lasting more than one round. The main issue I see is that the weight of the barrel, and the resultant torque from the tip whipping up and down after firing would likely crack the threaded portion off. That or the lugs the takedown pins go through would break or deform severely. Yeah, my main concern is the weight of the barrel, and you have a good point about the harmonics. I will probably get a 10 or 11” pencil barrel. Do you know what it takes to upgrade to nylon? Buddy said something about a precisely controlled environment being necessary w Nylon or carvon fibre. Maybe there is a Business that will print files you send to them?? |
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Posted: 2/23/2019 1:07:19 AM EDT
[#9]
Quote HistoryQuoted:
SLA materials are nice, pretty, clean and brittle. They are good for fitment parts and to show parts at trade shows and such. They are not enfgineering grade materials. I wouldn’t ever try an SLA part for function testing an upper. Maybe DMLS but that would take a lost of secondary operations to smooth out the internal features of the upper. This is what I do for work and have had people ask the same question. Ill probably still have him print it for fittmebt and modeling purposes but would have to get something else. made for prototyping. Are there services that will print one offs in some thermally stable CF for a guy? |
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Posted: 2/23/2019 1:16:19 AM EDT
[#10]
Quote HistoryQuoted: It...doesn't have to? I would hope the barrel, barrel extension, and the lugs and bolt are containing the pressure and not the receiver. The receiver just ensures the stability of components and guides the bolt carrier. You think the aluminum of the upper is any stronger than the steel it holds together? You all forget that Bushmaster made a glass-filled nylon upper receiver once. Not terribly durable but it wasn't a bomb. OP, as long as its properly in battery, I don't doubt it will fire once. From what I understand PLA is very soft and low-temp. I would try to find someone who can at least print it in Nylon, that stands a better chance of lasting more than one round. The main issue I see is that the weight of the barrel, and the resultant torque from the tip whipping up and down after firing would likely crack the threaded portion off. That or the lugs the takedown pins go through would break or deform severely. |
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Posted: 2/23/2019 1:21:07 AM EDT
[#11]
Quote HistoryQuoted: In this thread we see who doesnt know how an AR works |
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Posted: 2/23/2019 2:51:33 AM EDT
[#12]
Quote HistoryQuoted:
Big assumption you are making there. Quote HistoryQuoted:
Quoted: In this thread we see who doesnt know how an AR works |
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Posted: 2/23/2019 3:33:59 AM EDT
[#13]
Quote HistoryQuoted: Not reallly if you think the upper receiver is a “stressed part” in the lockup of the action. |
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Posted: 2/23/2019 4:30:53 AM EDT
[#14]
Quote HistoryQuoted: In this thread we see who doesnt know how an AR works |
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Posted: 2/23/2019 7:16:28 AM EDT
[#15]
Pulling the charging handle out of the gun changes nothing now pull the gas tube out then that will make a difference, (it will then be a single shot bolt action)
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Posted: 2/23/2019 9:56:54 AM EDT
[#16]
Quote HistoryQuoted:
Pulling the charging handle out of the gun changes nothing now pull the gas tube out then that will make a difference, (it will then be a single shot bolt action) |
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Posted: 2/23/2019 9:59:39 AM EDT
[#17]
Quote HistoryQuoted:
Feel free to try what I posted. It will change your face. Quote HistoryQuoted:
Quoted:
Pulling the charging handle out of the gun changes nothing now pull the gas tube out then that will make a difference, (it will then be a single shot bolt action) 
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Posted: 2/23/2019 12:44:45 PM EDT
[#18]
Quote HistoryQuoted:
Really? Here's a little experiment for you. Pull your charging handle out of your AR and fire it. Make sure you have a good NTCH proper shooting stance. How does that "no pressure" feel. By the way, learn to spell and think in complete sentences, it makes it easier to understand what your trying to ask. Quote HistoryQuoted:
Quoted: In this thread we see who doesnt know how an AR works How much psi do you think that little CH latch hanging on that little aluminum edge can take lol |
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Posted: 2/23/2019 1:34:09 PM EDT
[#19]
 This ones looking good already!
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Posted: 2/23/2019 1:38:20 PM EDT
[#20]
Quote HistoryQuoted:
Really? Here's a little experiment for you. Pull your charging handle out of your AR and fire it. Make sure you have a good NTCH proper shooting stance. How does that "no pressure" feel. By the way, learn to spell and think in complete sentences, it makes it easier to understand what your trying to ask. |
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Posted: 2/23/2019 2:15:25 PM EDT
[#21]
Quote HistoryQuoted:
You're talking about a jet of pressure coming out of the gas tube that is expanding into a relatively large void of free space, which by the time the gas key uncovers said gas tube, the ejection port is open, you know that massive hole in the side of the receiver? On top of that all that gas is going to be under the charging handle anyway, directing it to the ejection port. Quote HistoryQuoted:
Quoted:
Really? Here's a little experiment for you. Pull your charging handle out of your AR and fire it. Make sure you have a good NTCH proper shooting stance. How does that "no pressure" feel. By the way, learn to spell and think in complete sentences, it makes it easier to understand what your trying to ask. |
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Posted: 2/23/2019 2:38:48 PM EDT
[#22]
Quote HistoryQuoted: The gas key doesnt come off the gas tube till well after the bullet has uncorked. Sure the tube still spits a little something at your eye but you are moving the goal posts, that is nothing in the realm of 27k psi. How much psi do you think that little CH latch hanging on that little aluminum edge can take lol |
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Posted: 2/23/2019 8:00:15 PM EDT
[#23]
^
Dude, the slide pistol intercace is a moving part. The barrel is not a moving part. Thats just apples to apples. The pressure under the bullet is pushing back against the bolt, which is locked into the BE, which is screwed/pinned to the barrel... As previously discussed, weball agreed that use, under semi autobfire particular could cause the receiver to break in various ways. Sure some equalization of pressure bt the bore and atmosphere occurs after the action unlocks and ejects the case, none of that, alone, is blowing up anything. This is a new design, is why i am looking into the printing, sure a pla upper would not be a good alternative to real metal or CF upper. |
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Posted: 2/23/2019 8:41:15 PM EDT
[#24]
Quote HistoryQuoted:
^ Dude, the slide pistol interface is a moving part. The barrel is not a moving part. Thats just apples to apples. Quote HistoryQuoted:
^ Dude, the slide pistol interface is a moving part. The barrel is not a moving part. Thats just apples to apples. Quoted:
Now how about the surfaces the bolt rides along. |
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Posted: 2/23/2019 8:55:14 PM EDT
[#25]
Quote HistoryQuoted:
^ Dude, the slide pistol intercace is a moving part. The barrel is not a moving part. Thats just apples to apples. The pressure under the bullet is pushing back against the bolt, which is locked into the BE, which is screwed/pinned to the barrel... As previously discussed, weball agreed that use, under semi autobfire particular could cause the receiver to break in various ways. Sure some equalization of pressure bt the bore and atmosphere occurs after the action unlocks and ejects the case, none of that, alone, is blowing up anything. This is a new design, is why i am looking into the printing, sure a pla upper would not be a good alternative to real metal or CF upper. |
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Posted: 2/23/2019 9:10:12 PM EDT
[#26]
If you're just testing your upper for dimensional compatibility, might try running it w/ just a .22 LR adapter installed. But try to find a printer that @ least uses ABS, if not nylon.
Post pics! |
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Posted: 2/25/2019 4:07:28 AM EDT
[#27]
FOSSCAD has a couple of pistol caliber designs. (*Disclaimer: I haven't tried to make these)
Single shot .380 upper 9mm Shuty 3D Pistol Test firing at end of video.  Failed To Load Title eta: You can also download a 3D model of an AR from this arfcom topic. Each component is seperate so you could use that as a base to prototype (at your own risk) |
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Posted: 2/25/2019 12:42:23 PM EDT
[#28]
I would not attempt to print any gun part in PLA thats anywhere close to heat and force. I print my PLA @ 210 degrees C (410F). My bed is heated to 60C (140F).
So at 140, the PLA is soft enough that it deforms and sticks to glass. And at 410 it is so soft it can be extruded like toothpaste. Don't even start talking about how weak PLA is when its hard. Just think a bit about how easily it turns from a solid plastic part into pudding. You do not want to use it anywhere near any sort of explosion, especially 6 inches from your face. |
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Posted: 3/1/2019 2:40:42 PM EDT
[#29]
Quote HistoryQuoted:
Yes and the carrier/upper interface is a moving part. Whats your point? A steel carrier riding on plastic is not going to work. Are you that dense? You came seeking advise and then want to argue when the answers don't fit your wishes. I've been a FFL manufacturer for 40+ years, converted my first (of hundreds) of AR's to select fire in 1977. What your thinking will not work and is very dangerous to even attempt. Buy feel free to try just don't say you wern't warned and please don't have anyone around when you test it. I'll nominate you for the Darwin Award. Quote HistoryQuoted:
Quoted:
^ Dude, the slide pistol intercace is a moving part. The barrel is not a moving part. Thats just apples to apples. The pressure under the bullet is pushing back against the bolt, which is locked into the BE, which is screwed/pinned to the barrel... As previously discussed, weball agreed that use, under semi autobfire particular could cause the receiver to break in various ways. Sure some equalization of pressure bt the bore and atmosphere occurs after the action unlocks and ejects the case, none of that, alone, is blowing up anything. This is a new design, is why i am looking into the printing, sure a pla upper would not be a good alternative to real metal or CF upper. |
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Posted: 3/1/2019 2:41:57 PM EDT
[#30]
Quote HistoryQuoted:
FOSSCAD has a couple of pistol caliber designs. (*Disclaimer: I haven't tried to make these) Single shot .380 upper 9mm Shuty 3D Pistol Test firing at end of video.  https://www.youtube.com/watch?v=6bSLiFx36lk
eta: You can also download a 3D model of an AR from this arfcom topic. Each component is seperate so you could use that as a base to prototype (at your own risk) |
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