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MikeD's 450 Bushmaster build thread!!

I was going to rattle can camo this one but decided to break down and buy some Cerakote for the base layer. The camo will be be done with rattlecans. I cannot afford 4-5 colors or Cerakote. LOL

Thats going to add a little more time to the project but I'm really not in any hurry with this one and I think the end result will be better this way.

I think my next step will probably be 80% lower as long as I am taking the Cerakote route.
 
Using the cerakote as a basecoat would be better than using spray paints. The cerakote is a lot more resistant to common oils and cleaners and solvents that would find their way onto the gun.

I like cerakote and KG Gunkote, but I understand what you're saying. It's about $50 a 4 ounce bottle by the time you pay for the product and the shipping too.

But that 4 oz. bottle will easily do 4 or 5 complete guns as long as you're not wasting a lot with overspray and knocking it over on your bench spilling half of it :eek:

Looking forward to seeing how the lower turns out.

I felt like I just finished building a lightsaber when I got mine all put together.
 
The Cerakote came in this week. The process takes a fair amount of time so I want to get a few items ready. Plan on milling a lower this weekend.

I may or may not get through the painting process this weekend as well. Lots of prep involved and need to find a different method of baking than I used last time. Want to test out a small elec smoker thats been sitting in the garage for a while to see how well it can maintain temp
 
Cerakote isn't that bad to bake if you're worried about the smell.

If you leave it to dry overnight, there is little smell.

The longer you let it air cure, the less smell there is.

Throw it in the oven a few minutes after you paint it, yeah, Miss MikeD isn't going to be very happy with you.

I'm looking forward to seeing how the lower turns out the most. It took me several hours. I took my time, didn't get in a hurry and didn't even finish it in the same sitting either.

Check out pages 3-6 of this pdf. If you drill out more material with plunge cuts with the regular drill bits, there is less physical milling to do and easier. Just be mindful of the depth of your plunge cut.

https://www.ar-15lowerreceivers.com/content/80-Percent-Arms_Drill-Press-Jig-Instructions.pdf
 
I'm pretty sure you already have an 80 lower, but http://www.righttobear.com/AR15-80-Lower-Receiver-Cerro-Forge-W-Safet-p/80raw.htm have pictograph safety marking 80's for $45 each.

I thought about getting one, but I am holding off spending anything to save my money for an upcoming product that I have dreamed about for years. If he actually makes the product, but he said he has every intention to long as the numbers work.

Just to be honest, it's a new open bolt upper for my registered Mac 10.

Only, this upper is going to use a lot of AR parts and convert my 9mm over to essentially any AR15 caliber instead of just 9mm and 45acp that it's capable of now.

sneak peak, but this is the early prototype. It will be revamped and tweaked some so it'll have a continuous upper rail, etc., but this is a proof of concept to ensure safety and reliability first and foremost.

16" barrel

short barrel
 
Started working on my 80% lower today
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These are the side pates for the jig. The upper screws go thropugh the take down pin holes.

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This is the jig used to drill holes down through the main and rear pocket.

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These are the templates for the main pocket, rear pocket and trigger hole. They also have the depth gauge for the holes as well as the mill bit.

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Holes drilled into lower using jig. These holes help facilitate the milling process. I had a heck of a time drilling these holes. I am not used to working with aluminum but I went through 2 drill bits and it took a long time to drill these holes.

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Jig set up for milling the main pocket.

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The large top plate gives some surface for the router to sit stable.


Edit: Uploaded images to fix bad FailBucket links -MikeD
 
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Make sure the mill bit isn't clogged up with aluminum. Especially if the router was going at a high rpm.

Aluminum gets gummy when it gets hot, and tends to clog up mill bits.
 
Thanks, I'll check for that


Edit this was originally at the end of my previous post but the site onlu allows 10 pics per post so I moved it down here when re-adding the pics to this thread.

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Router set up and ready to start.

I am a little disappointed. I only milled down about 1/4 of an inch before the bit stopped cutting. I'm not sure If I was trying to take to much each pass or if I was just going to fast but I got to a point where it just bounced around and would not cut anything.

Between the problems I had drilling the holes and the issues with the mill I can say that this process is not as easy as they make it look in the video.


Edit: Uploaded images to fix bad FailBucket links -MikeD
 
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John, You Rock!! That worked. Got the bit cleaned out and finished it up. Pics coming in a few minutes.
 
I found I was trying to take too much off in each pass. My router has a dial gauge that allows pretty precise adjustment to the bit depth. I ended up dropping the bit 1/32 each pass after I got the bit cleaned out and it worked really good. It took a while but it cut clean and it greatly reduced the jumps and stutters. I think the most difficult pass was the last as it was cutting the entire floor of the pocket as I was at the bottom of the pilot holes.

I think the problem I had drilling those holes was due to going to fast and getting the aluminum to hot.


Here is a small portion of the milling process. Damn I hate my voice on recordings, not at all how I hear myself.

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Got the main pocket milled out.

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Got the rear pocket milled out. I did have to remove the rear screw from the jig for this, I had already reinstalled it by the time I took the picture.


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Drilling out the hole that will be used to start milling out the trigger opening.

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Ready to mill out the trigger port.

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Trigger port opened up.

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After drilling the hold for the trigger/hammer pins and the safety lever it's all done.

Needs just a little sanding to smooth out some of the edges but as far as milling and drilling it's complete.

This was an interesting endeavor.

Hey don't tell anyone I made this. LOL

Edit: Uploaded images to fix bad FailBucket links -MikeD
 
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That turned out great !!!!!!!!!!!! Matter of fact, you did better with your hand held router than I did my press and cross slide vise. I goofed a little on the hole for the trigger where it drops down out of the lower. When I reversed direction on my vise, the adjustments screws must've vibrated a little looser and it made my hole wider on one side than it was on the other. Still functional, but still irks my soul every time I clean it.

And I agree about the final pass to finish the floor is the hardest. If you don't mill it "just enough", the hammer won't fall because the nose of the trigger will bottom out on the floor before the hammer drops. If you mill "too deep" the disconnect won't catch the hammer right as the bolt brings it back when it's fired.

BTW, your jig is awesome on standard lowers too. I didn't know that it would accommodate a billet lower too.
 
I plan to test fit and function check the trigger next before I even start the prep for paint. I also want to check clearances to try and head off anything that will not fit with a layer of the paint applied. I would also like to test fire the upper to make sure I do not need to mill any more from the ejection port. All things that are easier corrected before I apply the Cerakote.

The billet lowers came from the same company that made the jig. They fit in there pretty good. I actually really like the machine marks on it. I may make another and just leave it shiny for a range gun.
 
Yeah, it would only take a few minutes to test fit everything and give it a quick function check. I agree that it would be wise to check everything first just in case you do need to tweak it a little, but from eyeballing it, I think you're golden.

Wouldn't hurt to throw the buffer tube assembly together so you can check to make sure the upper ejects when cycling by hand when you pull it forcefully too. I know you did it by hand earlier, but that was without the upper installed.

I believe you've got this.

I didn't need to install anti-rotational pins on my 80, but I did anyway. Eliminates worrying that a pin might walk out, and also ensures that over time the hammer pin doesn't egg out too. Just a little preventive maintenance is all.
 
I tried to do a bit of a function check on the lower and I am glad I did. When the trigger is installed there is no movement whatsoever. I will have to put it back into the jig and remove a little bit more from the floor of the main pocket.
 
The measurement you're going for measuring from the top lip of the lower to the floor of the FCG channel is 1.250"

I just measured my Colt, and it is exactly 1.2495" ;)

Remember, don't go too overboard with the 1.250".
 
I am at 1.1945". I'll pock it back into the jig tonight and fine tune it.

Aside from that everything seemed fit nicely.
 
Adjusted the depth so the trigger works now. I overshot a bit this time but it still seems to function good.

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Edit: Uploaded images to fix bad FailBucket links -MikeD
 
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Nice work Mike. Would you do it this way again? Or would you try a drill press/ mill setup?
I think with an actual mill I might have been able to do a slightly better job on the upper.

I have never used an actual mill so I really don't know if it would have been easier that way. It might have been a little less wear on the jig templates.

Using the drill press on the lower without some modifications to the press would probably have been troublesom, the small amount of play would have been exaggerated with the length of the bit and probably would not have made as clean of edges.

Overall, once I worked the bugs out it went really well and was pretty easy. Going slow and keeping the speed down on the router helped a lot.

One issue I had that I did not mention earlier is that the colet would work loose from the vibration of cutting the metal. Once I noticed this happening I would periodically stop and check it.

Yes I would do this again, and I will. ;-D
 
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