I recently ordered a jig and billet 80% lower receiver. For those of you who have successfully or unsuccessfully completed your lower let me know what you did or think or any tips, tricks etc. I do have a high quality drill press and access to some different milling equipment. Is it worth it to get an upper receiver for fitting purposes? I feel like I will get a better solid fit that way.
Yes I did a search, I found some stuff but I would like to know any up to date info.
Thanks
John
Take your time. Use step reamers to make your final hole sizes. Snap pictures and share with us your success!
I will take pics for every step and anything else that seems pertinent.
Anyone Else? I know some of you out there have done this
Paste a sign above the mill or drill press that says, "You can always take more off, sneak up on the final dimension slowly".
80% are easy, but like everything else in life, the first one is the hardest.
My plan is to sneak up and take the last off very slowly or by some sort of sanding procedure. As with most things on the internet there is an overload of info wether good or bad. I have a drill press with a Milling vice, not quite a mill but a little more than a drill press, I know the RPMs are not quite the same out of the press. Would I be better with a Polymer lower to start? Im not afraid to make a mistake and start over, new. What jigs have you all used? I am having second thoughts on the one I ordered.
if you can do it well, ok, but if it's a hack job don't feel bad, a completed one is easier to come by.
I am starting one now but have to lean on a relative in a shop to do it for me. I hate to ask for favors, but he has the equipment and said he can get around to it. Wish I had one to show him already finished so he can understand that will be done with that area. It would be nice to have a finished dimentional drawing to show him of what the final part should be since we have no jigs for these .308 DPMS style lowers yet. I guess its all a matter of who you know with equipment to get it done right. I would assume that after the maching the lower would have to be sent out for engraving for a model, caliber, fire/safe indicator etc. It might be cheaper to buy one already done and pay the FFL fees. I'll advise when its finally done.
I am starting one now but have to lean on a relative in a shop to do it for me. I hate to ask for favors, but he has the equipment and said he can get around to it. Wish I had one to show him already finished so he can understand that will be done with that area. It would be nice to have a finished dimentional drawing to show him of what the final part should be since we have no jigs for these .308 DPMS style lowers yet. I guess its all a matter of who you know with equipment to get it done right. I would assume that after the maching the lower would have to be sent out for engraving for a model, caliber, fire/safe indicator etc. It might be cheaper to buy one already done and pay the FFL fees. I'll advise when its finally done.
Last edited: Jan 31, 2014I am starting one now but have to lean on a relative in a shop to do it for me. I hate to ask for favors, but he has the equipment and said he can get around to it.
Be careful here, that wouldn't be meeting the intent of 80%.Be care full and don't hit the threaded ring the buffer tube screws into with the spindle when you make your final cut for the slot the rear upper rear lug goes into.
according to batf you have to cut the receiver. It is illegal to have someone cut it for you.
It is very easy. The first one i did came out a little rough on the inside but it works flawlessly. The second is mirror smooth and works flawlessly as well.
i would recommend getting a lower parts kit it will really help with final cuts. Also i would recommend at this time to order either anti roll pins or anti walk pins. They really help if the hammer or trigger hole walk a little bit.
Thats very interesting. I was not aware that you actually had to do it yourself. Oh well, will have to buy a jig now and put the drill press to work. I'll have him make up some type of vice or fixture for holding the workpiece though.
harbor freight sells a mill attachment for drill presses. let me find it. 6" Cross Slide Vise
its very similar to this. I did 2 lowers using only this a few drill bits and stopped at a machine shop supplier and got a 17 dollar 3/8's 2 flute mil bit 4 inch's long.
If its a computerized machine, anybody can program it as long as you hit the start button; or if its manual, he can babysit you and guide you while you physically make the adjustments.
I was just looking at the harbor freight mini milling machine. I have a drill press and an XY vice or cross slide vice, but I drill press is not the optimal tool for milling, the spindle is not meant for side loading, but I think if it is taken in small bites it will be okay. I have a jig and have been watching some of the better movies on youtube. Plus my jig and lower came with very detailed directions and measurements. It looks like its is almost idiot proof if you take your time and go at it slow and keep the metal cool as possible. I plan on starting tomorrow with the drill press and will try to get pictures that show the process.
harbor freight sells a mill attachment for drill presses. let me find it. 6" Cross Slide Vise
its very similar to this. I did 2 lowers using only this a few drill bits and stopped at a machine shop supplier and got a 17 dollar 3/8's 2 flute mil bit 4 inch's long.
Wondering what size and brand drill press you are using if you don't mind. You can PM me the info if you want. Looks like I am just down the road off of 1097.
thanks
its a really old one. i ran it on the slowest setting and bit very very slow. Did your jig have the drill plates with it or is it single stage with just the opening.
It is a newer design than the one I think you are talking about, it has a moveable plate and dual openings on the top, you start with the lower in one way, drill 16? holes and the trigger selector holes etc, then spin the lower the other way in the jig and use the removable plate and the existing opening on that side of the jig. it is a good, simple design as far as I can tell.
I have a jig and harbor freight mill. I messed up my first one as my vise wasn't squared up well enough and I ate into my jig plate trying to go too fast. got into the trigger pin hole area enough that I dint feel comfortable enough to build it. expensive mistake as it was a custom engraved 80% that I stupidly started with. got 3 more that aren't engraved but its currently too cold in the garage to mess with.
I plan on making at least one of these before I get another engraved for my sbr build. I had vaderspade engrave the 80% lower. I p[lan on just stamping my ssn into these with some steel number punches.
it makes it mine I guess.
I got into 80% lowers mostly as a way to have a true full custom lower with my dob or ssn as the serial number and engravings that mean things to me. going to have one engraved for my brother as well who just got selected into SF and when he comes down, he can mill it out on my equipment.
it also looks like a legitimate lower with a serial number to prevent the dumb questions at the local range.
Last edited: Feb 8, 2014For aluminum you should spin the 3/8 endmill at 2100ish RPM. the 1/4 should be at 3200RPM, but it should do just fine at the 2100. Yes it is fast but just remember to feed it slow. The high RPM will give you a much better finish. Also, there are two ways to mill: climb milling and conventional milling. Conventional milling requires less spindle power and is recommended for manual machines especially ones that have a lot of backlash in the table movement. Climb milling does require more spindle power and requires a tight and sturdy table (most CNC work is done climb milling), but it leaves a MUCH better surface finish. PLEASE LOOK UP CLIMB VS. CONVENTIONAL MILLING AND SEE WHICH ONE BETTER SUITES YOUR SETUP! Also make sure your final pass is .003 to .005, any less and it usually just rubs the material instead of cutting it. Make sure you have a way to get the chips out while you are machining.
The most important thing, though, is to know your setup and how it works. Make sure you are comfortable using it and have a little confidence with it. You want to know that when you turn the handle .005" that it will actually move .005" Don't be distracted by music or any other outside sounds, the sound the endmill makes while cutting will tell you everything you need to know.
FYI, I am a machinist by trade doing both manual and CNC machining. I do have a completed 80% lower that is now a functioning rifle so yes, I have done this before.
Last edited: Feb 8, 2014The reason is techenly unless the other person has a FFL they arnt aloud to so much as clean your firearm. Technically.
To get around that sell the 80% to your relative for a $1 then buy it back. That's how I do it when people need my help with stuff.
In round figure terms how much does it run to send a lower out for engraving? I have a set of stamps I could use, but they are a little bit on the small side. I was thinking about having it engraved with my name serial #0001, a born on date and getting it ceracoated.
Thanks for the info on the machining particulars and vice. This can be a fun project when it gets a little bit warmer in the garage. I still have my dads old but very high quality drill press.
Not sure which jig you have but I found them to not take enough out to fit the trigger & hammer in.
So when done, and before you tear it all down, check to make sure the trigger & hammer will fit. That way, if you need to take a few thou off the sides, it is easy to remove the top plate on the jig and do that.
Also, have the upper handy to check and make sure it will fit. Sometimes in your effort to be careful at the rear you will not take enough for some uppers at the rear lug.