AR-45 Lower Receiver

Project  |  History


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This website contains intellectual property belonging to CNC Gunsmithing / jwh02017

The AR45 design is currently patent pending

It's time for something a little bit different.  The same guy who shared with me his idea of the A1 detachable carry handle, William Putnam, also dreamed up another idea.  He wanted to use M3A1 "grease gun" magazines (which are .45 caliber) in an AR15 with a .45 cal. upper receiver.  Olympic Arms sells .45 cal. upper receivers but they come with a modified Uzi mag with a built-in mag well block.  The mag is single stack, so it's not real high capacity mag.  William was wanting to use the grease gun mag so you could have more trigger time between reloads.  The problem with using grease gun mags is that the body of the mag is about the same width as the outside of a normal AR15 mag well.  So you can't simply modify the AR15 receiver and expect it to work.  In order to get this to work, a brand new receiver would have to be machined from a billet of material to allow for a wider mag well.  One company has attempted this idea, but they used plastic receivers which aren't very versatile, as you can't change out the stock and pistol grip to fit your needs.  They also used a mag catch similar to that of the AK-47.  With that method, you have to hold the rifle with one hand, and then with the other hand grab and release the mag, then reach for another mag and insert it in the receiver.  I wanted to stick with a normal AR15 look and feel.  I wanted to be able to drop the mag by pushing the mag release button with same hand I am holding the rifle with while at the same time reaching for another mag.  This method would be alot faster than the AK47 style of mag release.  I also didn't want to move the location of the mag release button, since AR15 users are already familiar with it's current location.  So I started to work on the solidmodel design of the receiver and I came up with something I thought would work.  I'm going to call this new design the AR45.  It will be using an Olympic Arms .45 cal upper receiver.  In the pic above you can see how the mag well is wider than that of an AR15 receiver.  I'm not going to give a whole lot of details about how it's going to work just yet, but I'm 99% sure it will work.  I have already made a test piece and it worked perfectly.  As I get closer to finishing the receiver, you'll see exactly how this design is going to work.  


I started machining the 1st operation of the AR45 receiver.  I'm starting out with the same size block as I did with the AR15 lower receiver: 5" x 2" x 7.9"  Below you can see what the billet of material looked like in the machine...

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I first roughed the outside profile of the receiver with a 1/2" hog endmill and made a clean up pass with a 3/8" carbide endmill.  Then I used a 1/4" ball nose carbide endmill to machine the profile of the receiver.  In the pic below you can see how the 1/4" is starting to profile the receiver...

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Here it is a little further along...

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After some detail milling was done and some holes were drilled, the 1st operation was finished.  Below you can see what it currently looks like...

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I probably won't give a step by step of every tool I use while making the AR45.  That's because this receiver is very close to the AR15 lower receiver.  But I will show each operation along the way.  Some of you may have noticed the the spirals on the bottom of the receiver left over from the roughing process.  Always before hogging out material consisted of zig-zag and rectangular movements to remove the material.  The CAM software we use (Surfcam) just came out with a new way of roughing material, it's called Surfcam TrueMill.  This new technology manages the tools engagement with the material, so you never bog the CNC machine down.  So the CAM software now knows to slow down in the corners and speed up on straight line moves.  It also knows not to just plunge right into a square corner.  Instead, it kinda carves the material away until it reaches the corner of the pocket.  Before, a normal feed rate for hogging out material would be around 125 IPM, but now you can hit 650 IPM at a depth of 1/2" without breaking a tool!!!  We actually ran the test part that you see on the TrueMill website.  We ran the part on a Haas VF3 machining center.  At first we were afraid to crank it up to 650 IPM, but we kept speeding it up and speeding it up until we reached 650 IPM.  I couldn't believe my eyes.  I've been around these machines for a while now, and I have to say, I was simply AMAZED!!!  Here is a link to the Surfcam TrueMill website.  If you have a high speed internet connection, you really need to watch the movie about TrueMill.


For the 2nd operation, I'm going to be removing the slab of material on the right side of the receiver.  In order to hold the receiver flat and square, I used a pair of my old style AR15 setup blocks.  Since the mag well on the AR45 receiver is wider, I had to modify a couple surfaces on the blocks.  I could have used the new style setup blocks, but I had a set of the old style just laying around taking up space.  Here is a pic of what the block looked like in the vice...

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Here is what the receiver looked like at the start of this operation...

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I used a 1/2" hog endmill to rough the outside profile of the receiver.  If I didn't remove these pieces of material, the receiver would have the tendency to be jerked out of the vice while it's being flycut to the correct thickness.  Here is what it looked like after I removed these pieces of material...

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I then used a 3" shell mill to flycut the receiver to the correct thickness.  Then I came back with the 1/2" hog endmill to rough more of the material out...

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Next I used a couple more endmills, a drill, and a 1/4" ball nose carbide endmill to finish out the 2nd operation.  I haven't made the cut for the mag catch yet.  That will have to wait until further down the road.  If I tried to cut the mag catch now, I'll have a conflict on one of my other operations.  Here's what it looks like...

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Here's a few more pics of what the receiver looked like after it was bead blasted...

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For the 3rd operation, I'll be machining the top plane of the receiver.  This includes the fire control area and the magazine well.  I'll once again use a set of my AR15 setup blocks to hold the receiver in the vice.  As I mentioned before, these are a set of my old style setup blocks, but the current setup blocks I sell could have done the exact same thing.  In the pic below you can see how the receiver was setup in the vice...

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After using a roughing endmill and a few finishing endmills, I had the 3rd operation finished.  I only machined half of the mag well on this operation, I'll finish it out on the 4th operation.  The reason for this is because it's hard to reach the full depth with an endmill while at the same time keeping it from chattering too much.  Here's what the receiver looked like at the end of the 3rd operation...

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On the 4th operation, I machined the bottom of the receiver.  This operation also finished out the bottom side of the magazine well.  Here is what the start of this operation looked like...

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Below is a pic after the mag well was machined.  You can also see that the slots for the trigger guard were also machined...   

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Next, I used a 1/4 ball nose carbide endmill to 3-d profile the angle on the mag well.  Here are a couple pics showing what this tool done...

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For the 5th operation, I stood the frame on end and machined the buffer tower.  Here you can see the setup I used...

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And here is what the receiver looked like after the 5th operation was finished...

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On the 6th operation, I drilled the front take down pin detent hole.  Below you can see what the setup looked like...

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The 7th operation drilled and tapped the pistol grip hole.  I used a 2.5" block to prop the receiver up on one end.  This block made the pistol grip hole surface parallel with the machine.  Below you can what this operation done... 

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For the 8th operation, I drilled the buffer detent hole.  This hole is in at a 6 degree angle, so I had to prop the end of the receiver up.  To do this, I placed a 0.220" block under the front trigger guard surface.  Below is a sketch showing how this block was used...

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And here are a couple pics showing the setup and what the receiver looked like after it was drilled...

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On the 9th operation, I finished machining the right side of the receiver.  Here is where I machined the pocket for the mag catch.   I couldn't have machined this pocket on the 2nd operation, because there is a hole drilled from the top on the 3rd operation.  If this pocket was machined on the 2nd operation, it could have caused the drill to walk off position since the drill would have to pass through the pocket area before it finished drilling through the receiver.  Here is what the setup looked like...

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And here is the receiver after all the CNC operations were finished.  

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Notice the 5/16" hole inside the pocket.  This hole houses the mag catch spring.  This is the same spring from an AR15 mag catch.  When I designed this new AR45 receiver, I didn't want to make a whole bunch of new parts.  So to keep the design simple, I used the mag catch spring from the AR15.  This design is so simple that it only requires one new part to be made, the mag catch itself.  All grease gun magazines have a "D" or "square" shaped pocket on the right side of the mag.  So to catch the mag in the receiver, I designed the mag catch to catch inside this pocket on the right side of the receiver.  This will allow the same mag release layout as the AR15 receiver.  Before I started the machining on the AR45 receiver, I made a test part.  The test part would allow me to see how well the new mag catch design would work.  In this test part I made an aluminum mag catch.  The aluminum mag catch worked perfect, but it wouldn't hold up very long riding against a steel magazine.  So I made the new mag catch from 4140 chrome moly steel.  Below you can see what the new steel mag catch looks like...

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In the pics below you can see what the test part looked like.  

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I tweaked the mag catch design a little bit, and then I started on the actual AR45 lower receiver.  Since the machining on the AR45 receiver is now complete, I gave it a bead blasted finish and took some new pics before I started assembling the parts to complete the rifle.  In the pics below, I haven't drilled the bolt catch hole yet.  I drilled this hole with my AR15 drilling jig after I took these pics. (The AR15 drilling jig is for sale under the Tooling section at the top of this page).  

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There are two 1/2" roll pins that secure the mag catch in the receiver.  There needs to be two roll pins this length because you could never drive out one long roll pin because the lip from the mag well sticks out too far on the bottom of the receiver.  The pic below shows a close up of the mag catch pocket in the receiver.  

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I assembled all the parts on the lower receiver and attached my Olympic Arms .45 caliber upper receiver.  Now the rifle was complete and ready to be test fired.  Below are a couple pics showing the complete rifle...

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I grabbed a 100 round box of Winchester white box .45 cal. ammo from Wal-Mart and couple grease gun mags and I headed out to the field.  I had some .45 dummy rounds that I tested out first to insure the rifle would load a round properly, as well as eject it with no problems.  There were no problems with the dummy rounds, so I popped in a mag with live ammo.  I was kinda leery at first, because I didn't know what to expect since I had never shot a .45 caliber AR15.  I shot the first round, no problems.  I shot the 2nd round, no problems.  I ended up shooting the whole 100 round box of ammo without one problem what so ever.  Shooting the .45 caliber round in the AR15 is SWEEEET!!!  I enjoyed shooting it so much that I grabbed the extra ammo from my concealed carry, and loaded up another grease gun mag.  I didn't know the AR45 was going to be this much fun, otherwise I would have grabbed another couple hundred rounds.  The cool thing is, the AR45 isn't very loud at all.  I started out shooting with hearing protection, but half way through I decided I didn't them it.  It is no where near as loud as a .45 pistol.  After the testing of the AR45, all I can say is AWESOME!!!!

Below are a couple close up shots of the lower receiver...

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I'm now going to strip the receiver back down to bare aluminum and black anodize it.  I'm not 100% sure, but I think I may parkerize the steel mag catch.  I'll upload some more pics after the rifle is 100% complete.  


I decided to parkerize the new mag catch.  I ended up using some palmetto parkerizing solution that I left over from previous projects.  I used the manganese type solution.  Below is what a raw mag catch looks like compared to one that has been parkerized...

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I then black anodized the AR45 receiver and reinstalled all the parts.  Below are some final pics of what the rifle looks like...

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I finally got my short barrel rifle (SBR) and silencer paperwork back from the BATF for my AR45.  The whole silencer is made of  6061-T6 aluminum except for the stainless steel end cap that is threaded onto the barrel.  The aluminum parts are black anodized and the stainless end cap is just bead blasted.  Below are a couple pics of the silencer... 

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Here are a couple close up pics of the receiver... 

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And here are some final pics of the SBR AR45 with the silencer...

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I used a simple cone design for the silencer design.  The first time I shot the rifle, I was kinda disappointed, because I thought it was a little louder than what I was shooting for.  I've never shot a .45 silencer, so I really had nothing to compare it to.  I guess I was looking for "movie quite".  I then removed the silencer and shot the rifle, and WOW, man does the silencer make a difference.  After I shot the rifle without the silencer I became very happy with the silencer.  I would guess this rifle with the silencer sounds a little quieter than a .22LR.  It's kinda a different sound though, it's not that really high pitch sound like the .22LR has.  It's more of a low pitch sound.  This setup is not "movie quite", but it's quite enough for me.

BTW, the sights you see on this rifle is a HK diopter style sight that Centurion Arms sells.  They work great for close quarters with the AR45, and they really work good on AR15 rifles.  The best thing is they function just like a real HK sight, unlike some knock off sights you see out there.   

Below is a pic of Thomas R. Walsh of Falken Industries working a diplomatic protection detail in northern Virginia carrying an 8” barreled SBR AR45 he built using an original batch 1 CNCGUNS AR-45 lower receiver.

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--DISCONTINUED--  10% AR45 lower receivers - "paper weights" 

The 10% receivers will basically be the outside profile of the AR45 receiver, with most of the holes center drilled ("center drilled" means the holes will be pre-marked but not drilled) into the side of the receiver (from the 1st and 2nd operations).....and maybe have the buffer hole drilled and tapped. I'll machine half-way down inside the mag well on the top and bottom operations. This will leave a thin shelf of material (around 0.125" thick) that'll have to be knocked out (see pics below). And I'll of course have my AR45 mag catch design milled into the receiver, with the steel mag catch included. For instruction on how to complete the lower, you'll need nothing more than an AR15 lower blueprint. Everything dealing with the AR45 features will be done. Here are a few pics of what the 10%'ers will basically look like...

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100% and 80%  AR45 lower receivers

********** Please visit this link for the latest updates on the AR45 lowers **********

********** Please visit this link for the latest updates on the AR45 lowers **********

********** Please visit this link for the latest updates on the AR45 lowers **********

 

Click here for the AR45 PURCHASE ORDER form.  

Be sure to email me when sending payment  justin@cncguns.com

 

To get more details and to discuss the AR45 with others, then please visit the AR45 section in the forum.   

 

NOTE:  The AR45 uses unmodified grease gun magazines and a standard AR15 lower parts kit.  Grease gun magazines are manufactured with pretty sloppy tolerances so you may find some mags that fit the AR45 mag well just fine and then you might find some that are a little snug or won't fit at all.  If this is the case then it's an easy fix.... just determine if it's the width or the length that needs to be tweaked and then just simply squeeze the magazine very lightly in a vice.  I've purchased magazines from several different sources and I've never ran across a grease gun magazine that wouldn't work in the AR45.  

 

********** Please visit this link for the latest updates on the AR45 lowers **********

********** Please visit this link for the latest updates on the AR45 lowers **********

********** Please visit this link for the latest updates on the AR45 lowers **********

 

Below you will see what the finished product looks like.  The red lines in the photo is just there to hide the receiver info for this pic.

 

 

I've uploaded a couple videos to youtube showing the AR45 in action.  The first video shows how the AR45 functions with a slidefire buttstock.  The 2nd video demonstrates how a silencer can work on the AR45.  Click on the images below to watch the videos....

 

 

 


AR45 Upper Receiver Assemblies

 

I've had really good luck with the Olympic Arms .45 ACP upper receiver assembly.  Here's a link.  Since you will be using grease gun magazines with the AR-45, then you can save a little money by telling them you don't need their special .45 plastic magazine.  

 

The Oly Arms upper receiver assembly is a blow back system.  If you prefer a DI upper assembly then I would recommend buying a custom upper assembly from Rudy at Quality Machine   rudyk@maconarmory.com

 

 


This website contains intellectual property belonging to CNC Gunsmithing / jwh02017

The AR45 design is currently patent pending