Advanced 80% Receiver Jigs
There are many jigs to aid you in completing an 80% AR-15 (or AR-10/AR-308) receiver. One of the better examples of this style used to be the Easy Jig by 80percentarms.com. Then a step forward in jig technology became available from 5D tactical. This system offered much less drilling, more convenient depth setting slots, more accurate positioning of the jig with respect to the receiver, a larger diameter, better supported end mill bit, less swapping of jig parts during the milling process and a “touch free” guide system. All in all it was a significant step forward in 80% jig technology, and a similarly advanced Generation 2 (“Gen 2”) of the Easy Jig became available not long afterwards. As far as I know, these two are the state of the art in jigs at this instant in time (August 2017).
So which one is better? Ask and you’ll likely get one of three answers: 5D tactical, Easy Jig Gen 2, or “If you do only AR-15s then 5D else Gen 2”, and in many cases, the person responding has only used one of them, so their answer is suspect. I imagine that you can count the number of people who have used both on the thumbs of one hand, since neither one is inexpensive. I got the 5D tactical because at that instant in time it was the only one available, but upon finding out about the Gen 2, I thought it might address a couple of things I didn’t like about the 5D jig, but they were not significant enough to justify getting yet another jig. But it annoys me when people say one or the other is better unless they have actually used both of them. So I contacted 80percentarms to see if they were interested in me doing a head to head comparison, and they agreed.
Results from the comparison
After doing a receiver in the 5D jig and immediately thereafter doing an identical receiver in the Gen 2 jig, I found that both did an excellent job, much easier than the earlier technology jigs. However, in my opinion, the multi-caliber Gen 2 was a better choice for me.
Cost – If you are doing just a couple AR-15’s only, the 5D jig with aluminum side plates is the cheapest option; with steel plates, the 5D and the AR-15 only Gen 2 are price competitive. In order to do both AR-15 and AR-308, the multi-caliber Gen 2 is the cheapest option.
Ease of Assembly – The Gen 2 is slightly easier to put together; the biggest difference is the way the buffer tube socket is fastened in place. The disk used by 5D is more of a pain than the tube used by the Gen 2. Both jigs are designed to be used with a “palm” or “trim” router; the Gen 2 has an optional accessory to allow use of a full sized router.
End Mill – Both use an improved bit, which has the normal 1/4″ shank which expands to 5/16″ cutters. Furthermore, both are supported by a bearing at the base of the router. Bigger, better supported end mill bits cut better with less chatter and smoother finish. The 5D bit tapers from 1/4″ to 5/16″, which is the strongest methodology, but if you tighten the bit into the chuck onto the start of the taper, it will work its way out and cause severe problems. The Gen 2 steps from 1/4″ to 5/16″, which does not have this potential.
Guide Methodology – Both utilize a “no-touch” system where the router bit never touches the jig plate. The 5D uses two pins which ride in cavities on each side of the receiver. This works quite well, unless you allow the base of the router to rotate. Then the end mill bit can’t reach all the way to one side. The Gen 2 uses a collar around the end mill bit, which also works quite well and is unaffected by any rotation of the router base. Since the 5D uses pins of different lengths to limit where the milling occurs, you have to change pins once or twice (if you mill the take down lug cavity) during milling, and if you drop one of those small parts, it could take you a while to find it or replace it. The Gen 2 uses a “clevis” pin across the jig plate to control access to the take down lug cavity, and a bolt in sub-jig to control milling of the trigger slot.
Length Constraint – Both jigs “assume” that the length of the buffer tube socket is “mil-spec”. If it is longer, it will not fit into the jig. With the 5D’s solid jig plate, that means it cannot be used for these unless you mill slots into the jig plate. The Gen 2 end bar is bolted on, so you can compensate by putting pairs of washers between the end bar and the main plate. How much of a problem is this? Two of my three favorite receiver brands won’t fit into either jig without the modification.
Chip Control – The 5D throws chips EVERYWHERE. Using the accessory vacuum port on my router helped somewhat to about half the depth, where the accessory did not have much effect any more and the cavity was deep enough to mostly contain the chips. The Gen 2 built-in vacuum port worked much better and continued to remove chips all the way to the bottom of the cavity.
Drilling – Both were much better than the old style jigs where you removed much of the cavity by drilling a series of holes.
The 5D only required two holes, a 3/8″ hole to depth (using a drill stop) and a 5/16″ hole all the way through as a pilot for the trigger slot. The guide for the trigger slot pilot is not very thick, allowing the hole to be drilled at an angle. This leaves a scallop on the edge of the trigger slot; people on the forums have complained about this, and it happened to me as well. I strongly suggest using a drill press for this hole. If the drill is long enough, it can also dimple a built in trigger guard. Furthermore, it sounds like it could be a problem to start a 5/16″ end mill in a 5/16″ pilot hole, but since my hole was off center, I could not verify this. The drill guide does not have any way for chips to escape except out the top.
The Gen 2 only requires one 11/32″ hole all the way through to provide both functions. The guide is much thicker and seems to keep the trigger slot pilot centered, and prevents any built-in trigger guard from being dimpled. It does not seem necessary to use a drill press for this hole, and due to the height of the guide, may not fit into some drill presses. There are holes on each side of the guide for chips to escape through. Being smaller than 3/8″, it is harder to “find” the pilot hole with the end mill bit by feel; doing it visually, using a small bright light can help. You could not use a 3/8″ drill for this hole, as that would be wider than the trigger slot.
Milling – In both cases, the improved end mill bit cut very nicely (don’t forget your lubrication), and the suggested marks in the depth gauge were appropriate for a billet receiver. Forged aluminum is tougher and may require each pass to be shallower. The Gen 2 marks were a bit easier to follow, although when you get near the end of each gauge, they can also be hard to see without a light shining between the end of the bit and the end wall of the gauge .
In the 5D jig, keep an eye on the two screws applying tension to the buffer tube disk. When I was using this jig, the screws loosened, which allowed the receiver to move in the jig. This was discovered before any noticeable damage was done.
The final depth is critical, so I suggest that you double check the tightness of the end mill bit in the router (use a “real” wrench, not the toy which came with the router) AND the depth control of the router before starting and when changing from depth gauge 1 to depth gauge 2. It would also be a good idea to do this before each of the last few passes. I didn’t on my first one, and the cavity ended up .06″ too deep.
Pin holes – The final step is to drill the holes for the trigger group pins and the safety selector. The 5D side plates are 1/2″ thick and as long as they are steel, do an adequate job of keeping the holes perpendicular (but make sure to drill each side separately). The Gen 2 side plates are 3/4″ thick and do a bit better job of keeping the holes perpendicular. The Gen 2 has an accessory stabilizer which clamps to the side plate with one bolt to double the guide to 1 1/2″, which does an even better job of keeping the holes perpendicular.
Results – Both jigs provided a nicely finished, correctly sized cavity with much less work than older technology jigs. Both receivers accepted the LPK without difficulty, and functioned correctly. Both jigs can produce equal quality results. From a usability standpoint, the Gen 2 jig would be a better choice for many people, due to being slightly easier to use, significantly less messy, and providing fewer opportunities to screw things up.
I’ve got a long article with details of my experiences which is nearly complete; it should be published sometime soon. When it is, I will link to it here.