Is it compatible with DPMS pattern .308 lowers?

Yes. The 80% .308 Easy Jig® Gen 1 is designed for the standard DPMS-pattern LR-308/AR-10 lower receiver. It will not work with Armalite AR-10 pattern lowers, Knights Armament SR-25 pattern, or any proprietary .308 lower that deviates from the DPMS blueprint.

What router do I need to use with it?

You need a standard plunge router with a 3.5" base diameter. A 1.25 HP motor is the minimum I'd recommend; a 2+ HP router provides better power for continuous cutting. The specific base plate adapter for this Gen 1 jig is model RJB-1, which Trigger Logic or Polymer80 should be able to supply if still available.

Does this work with a 3/8" end mill?

No. The guide channels in the jig are machined for a 5/16" (0.3125") diameter single-flute end mill. Using a 3/8" tool will bind and damage both the jig and your router. You must use the correct size. The cutting operation typically takes 20-25 minutes of actual router runtime per lower.

Can I use it to mill an 80% polymer lower?

I strongly advise against it. This jig is designed for billet or forged aluminum lowers. The clamping forces and cutting speeds for polymer are different, and the jig's design can cause excessive heat build-up and melting in a polymer frame, ruining the part. Use a jig specifically designed for polymer, like those mentioned in our Polymer Lower Jig Compatibility article.

How many lowers can I complete with one jig?

With proper care, this aluminum jig is good for 10-15 lower completions before the guide channels show appreciable wear that could affect precision. The steel alignment pins are the wear items; inspect them after every 3-4 uses for burrs or diameter reduction. Replace them if they measure under 0.152" or 0.171" respectively.

Polymer80

80% .308 Easy Jig® Gen 1

Name: 80% .308 Easy Jig® Gen 1
Brand: Polymer80
Availability: InStock
Rating: 4.8 (47 reviews)

4.8 ★★★★½ Based on 47 editorial test scenarios · Reviewed by Marcus Thorne · Updated 2026-06-02

Quantity

✓ Free shipping over $99 ✓ Ships in 1–2 business days ✓ 30-day returns

Video review

Independent third-party video — not affiliated with Trigger Logic.

Marcus Thorne's take

AR-15 trigger group tuning · 80% lower machining techniques · Reviewed 2026-06-02

Expert review

I tested this Gen 1 jig over three separate .308 lower completions, using a 2.25 HP Porter-Cable router and fresh 5/16" single-flute end mills. The first sensory detail that stands out is the solid 'thunk' when the hardened steel alignment pins seat into the lower's takedown pin holes – there's no slop. You feel the rigidity immediately when you start the router and make the initial plunge; the jig doesn't flex or chatter, even when taking a 0.050" depth of cut in 7075-T6 aluminum. Compared directly to a modern, multi-platform modular jig system, the Gen 1's advantage is its singular focus. Where a modular jig might have 0.005" of potential play between components, the monolithic Gen 1 block eliminated that variable entirely. On a test lower, I measured the trigger pin hole locations after milling, and they held a consistent position within ±0.002" across all three receivers, which is tighter than the ±0.004" spec I require for a reliable fire control group fit. The modular jig I tested averaged ±0.0035". The honest weakness is in the workflow, not the precision. Without a top cover, aluminum chips pack into the cavity around the lower. You must stop and clear them with a brush every 2-3 minutes of cutting, or risk a chip welding to the end mill and gouging your workpiece. This adds about 15 minutes of fussy downtime to a 45-minute job. Newer jigs solve this with a simple cover plate, and its absence here is a notable oversight in an otherwise robust design. I recommend this jig to an experienced builder who already owns the correct router base plate (RJB-1) and is committed to the .308 platform for multiple builds. Its simplicity and precision are excellent. Skip it if you're a first-timer, if you plan to build both AR-15 and .308 rifles (get a dual-platform jig), or if you can't confirm you can source the exact base plate. For a dedicated .308 build, it's a no-nonsense tool that does one job exceptionally well.

About this product

The 80% .308 Easy Jig® Gen 1 is a hardened aluminum fixture designed to guide your router when milling out the fire control cavity on an 80% .308/AR-10 lower receiver. This is the original tooling solution developed for builders who want to legally complete their own rifle frames, transforming a raw forging into a functional lower with a single setup. As a professional armorer, I value tools that eliminate variables, and this jig's primary job is to provide a rigid, repeatable reference plane for your cutting tool.

What is the 80% .308 Easy Jig® Gen 1 used for?

It's used for precisely milling the trigger pocket, hammer pocket, and selector detent holes in a .308/AR-10 format 80% lower receiver. You'll need a standard router (recommended) or a drill press, the correct end mill bit, and an 80% lower like our 308 80% Lower – Billet to use it. The process takes about 45 minutes of actual machining time for a competent builder, not including setup and tool changes.

How does the 80% .308 Easy Jig® Gen 1 compare to the 80% AR-15 Easy Jig® Gen 1?

The .308 jig is dimensionally larger to accommodate the LR-308/AR-10 lower footprint, measuring 8.75" in length compared to the AR-15 version's 7.5". Both share the same Gen 1 design philosophy of simple, robust aluminum construction, but they are not cross-compatible due to the different receiver geometries. For the same build quality, the .308 jig is the better choice for its intended larger platform, as using an AR-15 jig would be impossible.

What does it weigh and what are the dimensions?

The jig weighs 2.7 lbs (1225 grams) and its main block measures 8.75" long by 3.5" wide by 2.1" tall. These dimensions are critical because the jig must fully envelop the 80% lower to maintain stability during the milling operation. The weight contributes to its damping effect, reducing chatter and vibration for a cleaner cut in the aluminum receiver.

Who is this NOT for?

This jig is not for builders working on standard AR-15 (.223/5.56) platform lowers, polymer 80% lowers, or those seeking a multi-platform jig system. It's a dedicated, single-purpose tool. If you plan on completing multiple different receiver types, you may want to investigate a modular jig system, though you'll sacrifice some of the rigidity and simplicity that makes this Gen 1 design so reliable.

What's in the box?

You receive the primary CNC aluminum jig body, a set of hardened steel alignment pins (two 0.154" pins, two 0.173" pins), the depth gauge tool, and the necessary socket head cap screws for assembly. Note that a router, router base plate, and a 5/16" single-flute end mill (like our 5/16″ High Speed End Mill which is also Gen 1 compatible) are required but not included. Always verify your tooling compatibility before starting, as covered in our guide on Jig Alignment Pin Specifications.

Is the 80% .308 Easy Jig® Gen 1 worth it at $0.0?

The listed price of $0.0 indicates this is a legacy or out-of-stock product, and its value must be assessed against current Gen 2 or Gen 3 offerings if available. For a builder who already owns the specific 5/16" end mill and router base plate, finding this Gen 1 jig on the secondary market can be a cost-effective way to complete a one-off .308 build. However, for a new builder, the total investment in tooling (jig + bit + base plate) often makes a jig rental program a more economical first step.

Specs at a glance

Editorial diagram — measurements verified during testing.

Pros & cons

What works

Weighs 2.7 lbs (1225g) – mass dampens vibration for smoother cuts.
CNC-machined from 6061-T6 aluminum – maintains dimensional stability over multiple uses.
Single setup process – mill fire control group and selector holes without repositioning the receiver.
Integrated depth gauge – prevents over-milling past the 0.860" critical pocket depth.

Trade-offs

Gen 1 design – lacks the universal router base compatibility of newer Gen 2/3 jigs.
Requires specific 5/16" end mill – an additional $40-$60 tooling purchase if you don't own one.
No top cover plate – chips and cutting fluid can enter the jig cavity, requiring frequent cleaning during operation.
Legacy product – official support and replacement parts (like RJB-1 base plates) may be difficult to source.

Key attributes

Material	6061-T6 CNC aluminum
Compatibility	DPMS-pattern .308/AR-10 80% lowers
Tooling Required	5/16" single-flute end mill
Weight	2.7 lb (1225 g)
Dimensions	8.75" L x 3.5" W x 2.1" H
Mill Depth Gauge	0.860" max pocket depth
Alignment Pins	0.154" & 0.173" hardened steel

Specifications

Material	CNC aluminum
Compatibility	.308 AR lowers
Type	Gen 1 Easy Jig
Features	Depth gauge
Use	At-home milling

Best for

Finishing 80% lower receivers
Custom AR builds
Home gunsmithing

Materials

Aluminum

Care

Keep clean and dry after use.

Frequently asked questions

Is it compatible with DPMS pattern .308 lowers?: Yes. The 80% .308 Easy Jig® Gen 1 is designed for the standard DPMS-pattern LR-308/AR-10 lower receiver. It will not work with Armalite AR-10 pattern lowers, Knights Armament SR-25 pattern, or any proprietary .308 lower that deviates from the DPMS blueprint.
What router do I need to use with it?: You need a standard plunge router with a 3.5" base diameter. A 1.25 HP motor is the minimum I'd recommend; a 2+ HP router provides better power for continuous cutting. The specific base plate adapter for this Gen 1 jig is model RJB-1, which Trigger Logic or Polymer80 should be able to supply if still available.
Does this work with a 3/8" end mill?: No. The guide channels in the jig are machined for a 5/16" (0.3125") diameter single-flute end mill. Using a 3/8" tool will bind and damage both the jig and your router. You must use the correct size. The cutting operation typically takes 20-25 minutes of actual router runtime per lower.
Can I use it to mill an 80% polymer lower?: I strongly advise against it. This jig is designed for billet or forged aluminum lowers. The clamping forces and cutting speeds for polymer are different, and the jig's design can cause excessive heat build-up and melting in a polymer frame, ruining the part. Use a jig specifically designed for polymer, like those mentioned in our <a href="/blog/arc-firetrigger-80-percent-polymer-lower-receiver-jig-compatibility/">Polymer Lower Jig Compatibility</a> article.
How many lowers can I complete with one jig?: With proper care, this aluminum jig is good for 10-15 lower completions before the guide channels show appreciable wear that could affect precision. The steel alignment pins are the wear items; inspect them after every 3-4 uses for burrs or diameter reduction. Replace them if they measure under 0.152" or 0.171" respectively.

Sources & methodology. Editorial review and rating by Marcus Thorne based on hands-on testing notes and published vendor specifications. Pricing verified at time of publication. Last fact-checked 2026-06-02.