Hey there! I'm a new member here, but have been a big fan for many years. I'm working on a project, which is to build an AR-10. I just bought my 80% lower receiver yesterday and I wanted to get EVERYBODY'S opinion, especially those who have transformed an 80% lower for an AR-10 into a complete, fully functioning lower, what brand and model jig/complete tool kit you recommend to do the job. I'm sure that there is one jig/complete tool set that most of you prefer to do the job more so than any other and I just wanted to see what answer the majority of you give. It might be helpful for you to know that it is a DPMS style lower and that it is forged. If there is any other information you need for me to give for you to give a more accurate or precise answer, please feel free to ask me! I welcome all positive input. Thank you!!!
Looking for a jig...
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Varminterror
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My honest advice is to buy a lower, and skip the milling.
If you really want to do it just for the experience, great. Otherwise, it’s a colossal pain in the butt for no benefit.
If you really want to do it just for the experience, great. Otherwise, it’s a colossal pain in the butt for no benefit.
adcoch1
Member
I will chime in, even though my 80% is a AR-15. I wouldn't say they aren't worth doing necessarily, but your end result probably won't be as nice as a 100% receiver. I built mine to solve a minor build issue in my state while building my form 1 SBR. I really like my finished product. The jigs I bought from Daytona Tactical will work for a 308 sized lower also. There is a bit of a learning curve to them(make sure your pin holes are straight!) But think it all through and be careful, you'll end up with a serviceable lower.
BigBlue 94
Member
Howdy there. Ive done 4 80% lower AR15 receivers. I have a decent milling machine. Ive used the polymer 80 plastic jig and an Anderson metal jig. Ive tried the drill-a-bunch-a-holes method. I failed on the 2nd one on the plastic jig. Trigger pins were off.
The plastic jig is good for one time use unless you are VERY careful. The Anderson metal jig has now done 2 good ones and has plenty of life left. The instructions provided with the Anderson jig are pretty good.
If you dont have a mill, a drill press will work if you do the 40 hole method. But I found my bit wanting to walk on a few holes. A sturdy heavy vise is a must for the drill press work. It wont be as easy and you'll need a dermal tool.
The most recent one took me about 75 minutes, taking .090" deep cut passes with my lathe/mill combo.
The bits they provide are junk. You need a 9/32 drill for the trigger pins, 5/16 for the trigger hole, 3/8 for safety selector, and a 3/8" end mill. A 5/16 end mill is handy for the trigger hole but not required. This is for the AR15. I know nothing of AR10s.
Now, is it worth it? Thats a question only you can answer. Not having a milling machine would be a deal breaker for me. Especially when you can get a serialized lower for less than the cost of a blank and jig. But I enjoy it and my skills have progressed with each one.
The plastic jig is good for one time use unless you are VERY careful. The Anderson metal jig has now done 2 good ones and has plenty of life left. The instructions provided with the Anderson jig are pretty good.
If you dont have a mill, a drill press will work if you do the 40 hole method. But I found my bit wanting to walk on a few holes. A sturdy heavy vise is a must for the drill press work. It wont be as easy and you'll need a dermal tool.
The most recent one took me about 75 minutes, taking .090" deep cut passes with my lathe/mill combo.
The bits they provide are junk. You need a 9/32 drill for the trigger pins, 5/16 for the trigger hole, 3/8 for safety selector, and a 3/8" end mill. A 5/16 end mill is handy for the trigger hole but not required. This is for the AR15. I know nothing of AR10s.
Now, is it worth it? Thats a question only you can answer. Not having a milling machine would be a deal breaker for me. Especially when you can get a serialized lower for less than the cost of a blank and jig. But I enjoy it and my skills have progressed with each one.
wiscoaster
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No, the benefits are in the learning / knowledge gained and in the pride of accomplishment / achievement -- both worth some time, expense, effort and yes, frustration. But you're right if the end result is the only objective, and there's no value ascribed as to how one gets there.
Varminterror
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I guess if a guy didn’t take shop class in high school and doesn’t know how to run a router, and has never had any experience with a drill press, let alone a mill, but they believe they need to learn that skill for future use - which can only be developed by hogging out an AR lower… it’s drilling and milling, not engraving or checkering, there’s really not much to learn. Changing spark plugs in a modern vehicle is typically more complex and requires more knowledge than jig milling an 80% lower.
I agree with what others have said. Check laws and if you want the challenge. Go for it. I did not use a jig.
I have done a few of both.
I have a mill, Kurt vice, a full Kennedy tool box, and time in the T&D trade.
I used multiple prints to verify dimensions.
It was not impossible just took some time.
I have done a few of both.
I have a mill, Kurt vice, a full Kennedy tool box, and time in the T&D trade.
I used multiple prints to verify dimensions.
It was not impossible just took some time.
someguy2800
Member
I recently borrowed a friends 5d tactical router jig to do a bunch of AR15 lowers. Never done an AR10, but same process. I figured since he offered I’ll just get a lifetime supply of lowers for me and mine and whip them out. After doing a whole bunch it was a pain in the you know what and I hope to never do it again. I’m very experienced with milling and metal work. It’s not difficult, just tedious and unpleasant. I would not chose to do it again unless you have a specific reason to not want a traceable lower.
I agree with wiscoaster, machining an 80% lower is worth the learning experience. A good end mill is a plus but using a jig with a router and taking your time will yield good results.
But going further depends on your objectives.
One note, I've drilled some of the cross pin holes from one side that were not straight. It is a factor of how a twist drill works, or does not work. It is best to get a jig where you can drill these holes from both sides.
I've screwed up a couple 80% receivers here and there.
BigBlue 94
Member
Yup drill from both sides. And only about .25" deep on the trigger pins. Selector switch must be drilled all the way through so half from one side and half from the other.
One other little trick I picked up was that the rear takedown pin detent can be modified for easy stock installation. Simply take a 6-32 tap and run it down the detent hole in the back of the stock. Cut the spring so it sits about 1/8" down in the hole. Then use a 3/16" long set screw to retain the spring.
For those not in the machining trades, before ever using an end mill or router, you need to look up "climb milling" and avoid it like the covid. Climb milling can ruin your hours of work in a flash. Only the most rigid machines can successfully climb mill. My mill/lathe combo is 1500 pounds and is not capable of its except on miniscule sized cuts.
And any time working with machines or end mills, never wear long sleeves, loose long hair, jewellery, etc. That can lead to a deathly mistake.
Varminterror
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This is something which always has me scratching my head.
Given 3 years, “traceability” of a lower becomes a matter of credit card statements, regardless of whether it was milled at home or transferred from an FFL. If you’re ordering online, there’s more permanent traceability on an 80% lower than any F2F transfer of a serialized lower at an FFL.
Here is my take on milling AR lowers.
A drill press is definitely the wrong tool for the job and here is why. A drill press spindle and bearing were never designed for the lateral stress of milling operations. You will wear out or break something prematurely when using a drill press as a mill. Another issue is that most drill chucks have excess runout (wobble) that can also cause issues.
And how many people actually check their drill presses to make sure the spindle is perfectly square with the table? Most average users will not even check that. Also, how many will take the time to actually use a dial indicator to make sure any cross slide is squared up to the drill press? Again not many.
The best method short of an actual milling machine is to use a router and jig. And this method is far from perfect too. Most routers run at too high of spindle speeds for cutting aluminum. Unless you have a special end mill designed to run at router speeds, you will wear out or break them.
All of this information is based on my career as a journeyman machinist, journeyman tool and die maker and journeyman mill wright.
Now for building one to avoid a paper trail, that is a futile waste of time. Unless of course you use crypto or cash to purchase everything. We can use the ATF raid on Polymer 80 last year as an example. Not only did the ATF confiscate customer information to include shipping and purchase records, they also did the same to the companies that Polymer 80 uses to print labels and ship through.
Building your own firearm from scratch or from an 80% is a good learning experience for those that want to do it. I will say that you definitely need a good working knowledge of how each one you build functions first.
A drill press is definitely the wrong tool for the job and here is why. A drill press spindle and bearing were never designed for the lateral stress of milling operations. You will wear out or break something prematurely when using a drill press as a mill. Another issue is that most drill chucks have excess runout (wobble) that can also cause issues.
And how many people actually check their drill presses to make sure the spindle is perfectly square with the table? Most average users will not even check that. Also, how many will take the time to actually use a dial indicator to make sure any cross slide is squared up to the drill press? Again not many.
The best method short of an actual milling machine is to use a router and jig. And this method is far from perfect too. Most routers run at too high of spindle speeds for cutting aluminum. Unless you have a special end mill designed to run at router speeds, you will wear out or break them.
All of this information is based on my career as a journeyman machinist, journeyman tool and die maker and journeyman mill wright.
Now for building one to avoid a paper trail, that is a futile waste of time. Unless of course you use crypto or cash to purchase everything. We can use the ATF raid on Polymer 80 last year as an example. Not only did the ATF confiscate customer information to include shipping and purchase records, they also did the same to the companies that Polymer 80 uses to print labels and ship through.
Building your own firearm from scratch or from an 80% is a good learning experience for those that want to do it. I will say that you definitely need a good working knowledge of how each one you build functions first.
BigBlue 94
Member
Since routers spin so fast, a smaller diameter 2 flute end mill would be best. Like a 3/16 or 1/4" diameter. My milling machine has 4 speeds. I run my 4 flute 3/8" endmill at 550 rpms and the two flute at 1100. Those are the middle two speeds I have available.
But neither router or drill press is remotely good for the task, for the reasons you mentioned. And a good XY cross slide table for a DP is expensive. Cheap ones dont hold rigid enough. Also on a DP, the side load from milling will heat up the chuck arbor and the chuck will fall off from metal expansion.
The problem with wood routers is that they run anywhere from 7,000 to 20,000 RPM's which is too fast for aluminum.
And yes a good XY table is going to be expensive. Those cheap ones on Amazon won't hold up for very long or be very rigid. And you are also correct that a chuck that is pressed onto its arbor can heat up and fall off.
I would not personally run a 2 flute end mill at 7,000 + RPM's while cutting aluminum. Yes I know plenty of people have used routers to finish AR receivers, But there is also a lot that have messed up the lowers and/or broke the end mills too.
And talking about climb milling, that is another thing to avoid. Especially with small end mills. That is a quick way to break them. I had to educate my SOT/FFL friend on this recently. I also took the time to adjust all the ways on his milling machine and lathe for him.
someguy2800
Member
The trick is to use a cutter with a very high helix angle on the flutes. I learned this porting aluminum cylinder heads with a die grinder.
https://www.americangunsmithtooling...e-replacement-zrn-coated-heat-shrink-end-mill
https://www.americangunsmithtooling...e-replacement-zrn-coated-heat-shrink-end-mill
BigBlue 94
Member
Lol yeah, unless you are using an .025" endmill!
I snapped a 3/8 diameter carbide 5/16 end mill off at the flat the other day taking a very shallow cut. Had it extended out to do the trigger hole and decided to do some touch up on the buffer tube boss. Whack! It luckily flew toward the back shield on the machine and not my abdomen...
its even still usable.Lol yeah, unless you are using an .025" endmill!
The smallest end mill I have used is a 1/16" and I do NOT like using them. You look at it funny and it will snap off.
@gunnut08 Just make sure to get a good quality jig and use a quality router and end mill. Also make damn sure that you keep the pocket clean of chips as you go and use plenty of cutting fluid/oil. Keeping chips cleared out and using enough cutting fluid/oil is very important. If you fail do to either one properly then expect a bad finish and/or a broken end mill.
Thank you BigBlue 94 for the tips, tricks and specifications, but I just wanted to verify that the figures that you mentioned are applicable to an AR-10 lower specifically and make sure that these figures are not for an AR-15 buy mistake. I personally have no idea what the difference would be between one and the other, but I would expect that there would be a difference and I know it would be an easy mistake to make since the AR-15 is so much more popular than the AR-10. I just wanted to double check before I started drilling, tapping and cutting etc. Thanks again regardlessly!
BigBlue 94
Member
Same here. Kinda like a 2-56 tap...
BigBlue 94
Member
As I said earlier, I have zero knowledge of the AR10. Thats up to you to find out. But the bit about drilling the pins and selector so deep still rings true.
adcoch1
Member
All of the ar10 lowers I've seen are identical to an AR-15 where the 80% finish work is required. It's everything else that's different. Dang, now you got me thinking about an ar10...
someguy2800
Member
Honestly if you just want to do it to say you did it then more power to you, but unless you are planning to go into a career of making things with the wrong tools I’m not really sure this is even an educational experience. I don’t really see what you get from it over just assembling a stripped completed lower.
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