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The Luth-AR LRPK-BLDR is a builder-style lower parts kit made for anyone assembling an AR-15 who wants the little stuff handled but plans to run their own fire control group. It covers all the pins, springs, detents, and catches you need to bring a stripped .223 Rem/5.56 NATO lower to life, minus the trigger, hammer, pistol grip, and buffer system. That layout is the whole point here. If you already picked out a match trigger or a grip you like, you're not paying twice for parts you'll toss in a bin.
Most standard lower parts kits force a mil-spec trigger and A2 grip on you. This one skips those on purpose. You get the bolt catch and its spring, plunger, and roll pin, the magazine catch with button and spring, the safety selector with its detent and spring, both takedown detents and springs, the front pivot pin, rear takedown pin, buffer retainer and spring, and a pair of hammer and trigger pins. That covers everything the fiddly, easy-to-lose category and leaves the performance choices to you.
These are standard AR-15 components cut to mil-spec dimensions, so they drop into just about any correctly spec'd stripped lower on the market. Luth-AR builds its parts in the USA to mil-spec drawings and heat-treat standards, and the springs are made from certified 17-4 stainless and mil-spec steel wire, which matters most on the detent and catch springs that see the most cycling. A word to the wise on the build itself: keep a punch set and a little patience handy for the takedown and selector detents, since those spring-loaded pieces are the ones that like to launch across the room.
If you're pairing this with an aftermarket trigger and a grip you already trust, the LRPK-BLDR is a clean, no-waste way to source the rest of your lower in one shot.
No, and that's by design. This is a builder kit, so it leaves out the fire control group, pistol grip, and buffer system so you can install your own trigger of choice. You will need to supply a trigger, hammer, and disconnector separately, along with a grip and buffer/stock setup.
In almost every case, yes. These parts are cut to standard mil-spec AR-15 dimensions, and nearly all currently available stripped lowers are machined to accept them. As long as your lower is a correctly spec'd AR-15 receiver in .223/5.56, compatibility should not be an issue.
A complete kit includes a mil-spec trigger, hammer, disconnector, and usually an A2 pistol grip. The LRPK-BLDR skips those items so you're not paying for parts you plan to swap out anyway. It's the smarter buy if you already have an aftermarket trigger and grip picked out.
It's very doable with basic tools and some patience. The trickiest steps are the spring-loaded takedown and selector detents, which can pop loose if you're not careful. A roll pin punch set, a good bench, and a build video are all you really need to get through it.
| UPC | 859992007654 |
|---|---|
| Manufacturer | |
| Manufacturer Part Number | LRPK-BLDR |
| Caliber/Gauge | .223 REM/5.56 NATO |
| Product Type | Lower Parts Kit |
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