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.380 Blow Back Hand Gun
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  Tanner Frisby

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Posted: April 07 2016 at 3:50pm | IP Logged Quote Tanner Frisby

Hello all,
It has been quite a while since I last visited this site and my last content contribution was in late March of 2014, over 2 years ago. The website is as slow as ever, but it is nice to not be greeted with a Parallels H Sphere web page. For those of you who remember me, I'd like to share what I've been up to. To the rest, gun stuff starts with the first picture.

I took on a side project that is taking longer than expected. In order to learn automotive, I decided to try and build a car. The summer project turned to fall and spring saw me move to Singapore. Singapore being stringent on both automotive and gunsmithing, I had plenty of time to design this build and start constructing a website under my own domain ( www.tannerfrisby.com ). [As an aside, I was watching a Forgotten Weapons on youtube in a courtyard on campus at National University of Singapore, because it was a nice day outside, when I was confronted and questioned by campus officials on suspicion of terrorism as I was reported to be "watching videos on how to load a gun". What a completely different world.] Late summer and the car building continued and then fall came again. Now I have moved away from my college campus again which has limited my ability to work on my home brew car. This new free time has been filled once again with gunsmithing. And work. And lots and lots of homework from graduate school night classes.

The car (build thread here ) has paralleled my studies in undergraduate mechanical engineering very well. The additional classes have also aided in my gunsmithing (as well as general mechanical knowledge). My previous builds have been a little lacking in quality and function to the point that either my skill or expectations would have to change. Now, I've invested in a Seig X2 style mill and refined my machining skill through working part time in a machine shop on campus.

My grand plan for this build was to film and time lapse the build while breaking it into 20 minute videos showing the steps of construction in all aspects of building the gun. I'll call this a trial run and go through with it on the next build. One thing I did learn was that filming and editing makes the builds go about 4 times as slow as just photographing and writing up an article like this. Which leads to the next problem.

Today is my 21st birthday which in the United States means that I can now legally (unless otherwise barred) consume alcohol and purchase both handguns and handgun ammunition along with applying for a concealed carry permit. My goal was to finish this handgun by today (which I realized wasn't feasible about 3 weeks ago) and have a .380 handgun as a candidate for concealed carry.

I stopped filming pretty early on in order to try to reach the 21st birthday deadline and then all but stopped documenting as he date grew nearer. There is a large portion of the frame machining that is omitted. I apologize for that.

Assuming this build works out well, I haven't decided whether to release the build documents and drawings. This was initially the plan along with a detailed how to write up. For reasons I'll explain later, I'm not sure whether it is in my best interest to do this or not.

___

But now to the build. This build is a .380 handgun, single stack 6+1, built with a 4140 slide / barrel and a 6061 frame / internals. The final gun should be 4" or so from top of slide to bottom of grip, 6" from muzzle to back end and .75" at its widest point, no protrusions (smooth on both sides), no last round hold open.



This block here is to become a trigger. After milling the block true and to dimension, two holes were drilled. One to pivot the trigger on (the front hole) and one for the disconnector. The digital inclinometer is used to set the angle for the next machining operation.



Here the inclined plane is milled to a depth prescribed on the trigger block.





The trigger profile, which is mostly aesthetic, is drawn onto the block.



The profile is then roughed on the mill and later filed by hand.



This cut is required and is also used to index a symmetric cut (next picture).



Using a piece of paper to offset the trigger block from the vise's face, the mill's z-axis is locked in place.



And here is a picture of the mill itself.



The trigger is now finished milled and filed smooth.



This was the first part I made on the mill. It was chosen due to its relative simplicity to help me get a feel of the machine I would be using to make the rest of the build. I learned some of the basics of the feel and handle of my X2 mill, but not enough to prevent myself from breaking plenty of tooling through later mistakes.

___

Now onto the frame:



After sawing through the aluminum plate (manual hack saw, very tedious) and truing up the cut and factory edges, the block was set to the proper angle using my digital inclinometer (within the .30 degrees tolerance)



Two different angles are prescribed here. This first angle (the one cut in the above picture) is normal to the magazine. The second angle is parallel to the base of the magazine.



A 3/8 end mill is used to start the magazine well.



Followed by a 3/8" drill through.



The drill through is important as it is used for indexing the frame when flipped over. Not all of the tooling used (very little in fact) is long enough to span the hole 5.5" or so.





Next, a 1/2 end mill is used to machine a base normal to the hole for the next drilling operation.



A smaller drill bit was used for most of the magazine well aluminum removal.





Flipping the frame repeatedly doesn't cause any alignment concerns when I can index off of the through hole.
Here I am center drilling for the 3/16 ish size hole that will be drilled half way through and meet the hole on the other side (I managed 6 for 6 which I though was pretty impressive).



With all holes drilled, it was time to remove the rest of the aluminum.







An end mill was able to remove almost all of the aluminum, but didn't quite make it to the half way point.



Now I am cutting the the second angle (the angle that is parallel to the magazine's base plate when the magazine is inserted).
In this picture I am removing metal by turning the y-axis (towards and away from the operator). Little did I know what would happen next.



The vise I am using is called a quick set vise. It has its advantages and disadvantages. One of the disadvantages is that it can't grip the work piece well if the work piece is only gripped on one side of the vise as opposed to both sides or centered in the vise.





You may notice two distinct sets of striations. I reset the angle and cranked the vice down as tight as possible. It happened again.

The solution ended up being relocating the frame so that the vise was able to grip the frame from both sides (as shown above).





The next step was to cut the frame rails with a woodruff key cutter. I started the build off by estimating the hardest machining operations along with the points I was most likely to irrevocably mess up the build. I figured slide engagement and magazine well would be the hardest two machining operations so I made sure to do them first. No point in scrapping the build at the end after I've done all the safer machining steps.



By being a little too hasty with the feed rate, I broke my first end mill: 3/32" carbide square end mill. Many, many more to come.



Abandoning the ejector slot for now (I only had one 3/32 end mill) I progressed to the barrel end of the frame.



Next came the third mistake of the build. I machined off the front end of the rail prematurely and out of sequence. Had I machined it directly after machining the hole for the mainspring then I wouldn't have had this potentially problematic hole break through.



But the problem wasn't too devastating and ends up being procedural only. The build is able to progress as if the order of operations had been observed properly.



The mainspring will be from a Khar P380, as I was able to measure the dimensions of the mainspring prior to designing the build. With that said, I haven't purchased the mainspring(s) at this point.





Well, broaching without the proper materials "worked" but still needed plenty of filing afterwards.
I didn't have a block of iron to machine and taper to shape, so I tried hammering a piece of angle iron through the magazine well, realigning it ever millimeter or so.





Using my Colt Mustang / Sig P238 magazine with Sharpie dykem, i eventually filed the magazine well to shape. The magazine requirement was single stack, 6 - 7 rounds, no grip extension at the bottom (flat standard bottom plate) and cheap. This led me to the Sig p238 and colt mustang magazine (basically interchangeable).
Next, I continued to file another .002" off all sides of the magazine well to account for the anodizing later on. To test for this, I wrapped the magazine with scotch tape to add the requisite thickness and kept filing until the thickened magazine slipped out of the magazine well by gravity alone.





Next operation to deal with is the magazine release. This marks machining error #4. I don't have the ability to machine angles easily. This requires me to manually cut angles by modulating the x- and y-axis (again, by hand) at the proper relative rate at the same time. With a little trigonometry, it isn't that hard to determine the rate at which you turn one axis with respect to the other. The problem came when I rotated the y-axis counter-clockwise instead of clockwise giving me my 10 O'clock cut instead of my needed 8 O'clock cut. Lucky for me again, this error will be hidden on the final product and can be accounted for by modifying the magazine release.







Now the magazine is properly machined. There will need to be a little more work at the end to make the gun feed right, but for now I'm pretty happy with it. The magazine well is a little bit plus sized, but I think I did a great job with the file. I have a slight taper opening at the bottom to help with magazine insertion. I probably tapered a little too much though.



Now with my new shipment of (quantity 5) 3/32 carbide end mills, the ejector slot has been machined.



And now we have machining error #5: I over cut the barrel seat. Internal sharp corners are very hard to machine, so generally a machinist will over cut with a small diameter cutter to achieve the 90 degree faces. I did that as well but had a miscalculation in my distances; I over cut by a diameter on each side instead of just the radius I intended. Again though, this isn't a critical error and, like the rest up until now, won't show through on the final product (unless you disassembled it, etc.).



While I intended my Sharpie to act as Dykem, it seems to also double as liquid penetrent. Both feed lips are cracked, which makes the magazine wider at the top as a function of the number of rounds in the magazine. More rounds = more compressed spring = more normal force between the top round and the lips holding it in them magazine (gets harder to load) = more deflection of the magazine lips = wider magazine with each new round added.

I've since purchased a new magazine, but I'm going to use this one until I finish the build. It still works as a magazine (mostly) but it is the kind of magazine you take to the range instead of keep in your pocket as back up.

I'm pretty sure I messed this one up fitting the magazine well. I would be hesitant to blame the manufacturer. This shouldn't be a negative reflection on Colt Mustang magazines.





I machined down three non-adjacent faces of a 3/8 x 16 nut such that the apothem to a machined face is .25". Next, I ground the threads down to about .35" OD.



And then I bolted a short section of my Green Mountain Gunsmith Edition 9mm barrel (~1.08 OD) into the half inch chuck of my mill.
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__________________
5 most recent builds as of this post:

.380 Blow Back
Vetterli Rifle
7.62 x39 v2
7.62 x39 v1
Mosin Nagant

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  Tanner Frisby

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Posted: April 07 2016 at 3:50pm | IP Logged Quote Tanner Frisby





Next, with the angle grinder chucked up in a different vise and a grinding wheel installed, it is time to rough up this barrel.



This is the first time that I've done a machining operation where not only the work but also the tool takes meaningful wear. I first made the top most grind, followed by the bottom most and successively upwards back to the top. Each groove was successively shallower as the grinding wheel disintegrated with an increasing rate (quadratically).



Final grinding was accomplished using a cut of disk. The cut off disk has less variation in diameter across its thickness, but is also more susceptible to deflection, which skews tolerances.



Not counting the 1/3 that was to difficult to reach, the thin film of grit on everything in the garage or the portion I inhaled, this is the powdered barrel.





The barrel was ground to 0.5" diameter. A slightly less thick portion of the remains of the barrel was rough cut to be machined to match the ground barrel diameter.



And then stupid mistake number 6: I pock marked my vise by being too lazy to get a more appropriately sized parallel. For those who aren't machinists, this is a big no - no. That part of the vise is known as the "dead jaw" because it doesn't move and is taken as the datum (the mill's 'origin' which all measurements are take off of). It is important to keep the vise, and more specifically the dead jaw, as true as possible and to not do this to it.



Immediately followed by error number 7: burning up my 1/4 HSS end mill. Blue chips should have told me I was going a little hot. The end mill still "works" but it doesn't cut like she used to. I am machining the prehardened 4140 slide in the above picture. This mill definitely wasn't built for machining hardened steel.

__________________

And this marks the lapse in documentation. For almost a month, I spent my few free hours machining instead of machining and documenting. Because of that, few pictures are taken of the slide's machining. I will say that I broke at least 4 carbide 3/32 end mills trying to mill deep slots in the hardened 4140.

__________________



This is probable mistake #13 (plus or minus 2).
I forgot how I clamped up my work piece. I thought the dead jaw (my y-axis zero) was in contact with the rails (where I took my measurements from). As such, all the follow operations are ~.3" off. This is probably the closest to a terminal screw up I've come into yet.

______________

Again, a lapse in picture taking until two days before my 21st birthday.

______________








Needless to say, this "endmill holder" didn't work. It was a long shot, but I didn't have anything better at the time.

My 3/8" end mill needs to be about 2" longer than it is, but the hole that the end mill goes into is 0.5" OD, which severely limits my tool holding choices. I knew I'd have to make one but the sharpie was the only thing I had on hand and hey, it was worth a shot right? Way to flexible even for the very limit work I needed it to do (a few thousands of metal removal).



Now with the end mill removed from the sharpie corpse, the feed ramp was milled into the barrel.



Here's how she sits right now. As you can see. Many, many operations were glossed over when the picture taking stopped. I apologize for this and will attempt to supplement the missing pictures with close ups and narration before this is all done.



After many attempts, I was able to get my snap cap to meander into the barrel. The snap cap hangs up right here though (until I get my 3/8 end mill holder working and can remove those few thousands I mentioned previously)



And here is the business end.






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More content to be added as the build progresses.
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__________________
5 most recent builds as of this post:

.380 Blow Back
Vetterli Rifle
7.62 x39 v2
7.62 x39 v1
Mosin Nagant

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  Tanner Frisby

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Posted: April 07 2016 at 3:51pm | IP Logged Quote Tanner Frisby

Place holder 2
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5 most recent builds as of this post:

.380 Blow Back
Vetterli Rifle
7.62 x39 v2
7.62 x39 v1
Mosin Nagant

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  bikergunnut

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Posted: April 07 2016 at 10:02pm | IP Logged Quote bikergunnut

Welcome back and HAPPY BIRTHDAY
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  backbencher

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Posted: April 07 2016 at 10:46pm | IP Logged Quote backbencher

Welcome back! What magazine are you going to use?
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  Paraquat

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Posted: April 08 2016 at 8:11am | IP Logged Quote Paraquat

Just don't stance the car.
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  Tanner Frisby

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Posted: April 08 2016 at 10:35am | IP Logged Quote Tanner Frisby

bikergunnut wrote:
Welcome back and HAPPY BIRTHDAY


Much appreciated. Yesterday didn't see any gambling or drinking, but I put my name down on my first handgun and bought 100 rounds. The frustrating part? I wasn't even carded

backbencher wrote:
Welcome back! What magazine are you going to use?


The magazine is from a Colt Mustang, but is apparently identical to the Sig p238. I chose it for these reasons: single stack, 6 - 7 rounds, no grip extension at the bottom (flat standard bottom plate) and cheap. Availability is another requirement but I feel like it was a given when paired with the previous conditions.

Paraquat wrote:
Just don't stance the car.

You don't like disfunctionally modified vehicles?

_____


I'm aiming for 50 pictures per front end post and will edit accordingly. If I go over 150 pictures, I'll divvy up the surplus across the three front end posts. I've always disliked wading through comments in build threads to get to OP's posts across 20 pages of thread. I'll still post when I've made an edit and address comments, but I'm going to try to have all the "build" at the top of page one.

With that said, I've updated to the current state.

Thanks,
Tanner Frisby
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__________________
5 most recent builds as of this post:

.380 Blow Back
Vetterli Rifle
7.62 x39 v2
7.62 x39 v1
Mosin Nagant

  Status: Offline
View Tanner Frisby's Profile Search for other posts by Tanner Frisby Visit Tanner Frisby's Homepage
 
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