Anderson Manufacturing AR-15 Lower Parts Kit - Stainless Hammer and Trigger

MPN: G2-K421-A000-0P
Manufactured by Anderson Manufacturing
81 Reviews


Out of Stock

NOTE: Limit 2 per household. Quantities exceeding 2 will not allow checkout.


Out of Stock


Anderson Manufacturing builds rifles, pistols, and parts utilizing the latest in computerized manufacturing. By keeping manufacturing in house, Anderson can offer quality, American-made products at an affordable price, backed by a limited lifetime warranty.

The Anderson Manufacturing Lower Parts Kit contains almost everything you need to assemble a stripped lower receiver. Just add your favorite stock kit for a complete lower receiver!

This MIL-SPEC parts kit is precision machined for a drop-in fit with nearly all lower receivers on the market. Features the Anderson Manufacturing stainless steel hammer and trigger set with a lightened speed hammer for improved lock time!

Kit includes:

  • (1) Stainless steel hammer
  • (1) Hammer spring
  • (1) Stainless steel trigger
  • (1) Trigger spring
  • (2) Hammer/trigger pins
  • (1) Disconnector
  • (1) Disconnector spring

  • (1) Bolt catch
  • (1) Bolt catch plunger
  • (1) Bolt catch roll pin
  • (1) Bolt catch spring

  • (1) Buffer retainer
  • (1) Buffer retainer spring

  • (1) Magazine catch
  • (1) Magazine catch button
  • (1) Magazine catch spring

  • (1) A2 pistol grip
  • (1) Pistol grip screw
  • (1) Pistol grip lock washer

  • (1) Standard safety selector
  • (1) Safety selector detent spring
  • (1) Safety selector detent

  • (1) Takedown pin
  • (1) Pivot pin
  • (2) Takedown/pivot pin detents
  • (2) Takedown/pivot pin springs

  • (1) Trigger guard
  • (1) Trigger guard roll pin


BrandAnderson Manufacturing
Manufacturer.Anderson Manufacturing
Weight8 Oz

WARNING: This Product can expose you to chemicals which is known to state of California to cause Cancer and Reproductive Harm. For more information, see

Great kit with a hidden gem

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Personally, I think this is the best LPK on the market. The trigger is what stands's worth $40 by itself. Out of the box, the trigger measured exactly 5lbs on my Wheeler Professional, with a short takeup and crisp break. However, I then paired it with a $10 JP Enterprises spring kit, and now it's measuring at 3.4lbs and feels even better. I've used CMC triggers for years, and this is every bit as good for under $50 ($40 if you buy the trigger alone). The rest of the parts are fine...they aren't anything special or fancy, but they fit great and they do the job. I've installed these on about 20 different builds, though admittedly most of them were with Anderson lower receivers, and have never had fitment issues. If you just need a basic mil-spec kit and/or want a gem of a trigger, look no further.


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The kit is packaged nicely. The hammer I received had a broken J spring, so the hammer pin was walking out. I emailed Primary Arms, and they had Anderson send me a non-defective hammer. The trigger pull is very short and crisp for mil-spec. Selector is tight, but I kind of like it. Only the front pivot pin is dimpled, not the takedown pin, which is weird to me. Overall, decent.

Great LPK, Great Price, PA never fails to satisfy!

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Having purchased and installed many of these Anderson LPKs, I can confidently state that anyone who has issues installing LPK this needs to stick to their Lego's and leave the smithing to those of us who know what we are doing. Milspec is milspec, not perfection in a box. Drop in parts are not always drop in. Compared to working on 1911's, installing AR parts is a breeze.
<br>Enough said. Buy this kit, you will like it.


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I wish I had read some of the reviews for The skit before purchasing. I generally purchase Aero lower kits. The one I liked was not in stock, so I went with this kit. Bolt catch spring did not fit. Ended up ruining the spring trying to fix it. Now I have to order another bolt catch spring before I can go any further. Won't be ordering anything else from Anderson

A solid LPK

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This is a decent kit which I installed into an Aero lower with a JP spring kit. All the parts look well machined but I ran into an issue with the hammer. Once installed the hammer would not move without considerable force. I had to sand down and polish both sides that have the slot for the trigger pin. A few minutes of work and this is a solid kit. I will buy again if on sale.

AWESOME LPK, especially with a few cheap upgrades

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I like everything about this kit.
<br> STEAL at the sale price.
<br>+ Stainless, well machined trigger and hammer.
<br>+ Hammer is bobbed, so you can add a reduced power hammer spring and still get 100% reliable ignition, while reducing pull weight.
<br>I had a bunch of Magpul MOE grips laying around I bought last year for 5 dollars each, a JPE reduced power enhanced reliability spring kit, and a 1/4-28" set screw with a shortened pistol grip screw.
<br>I didn't even have to polish the engagement surfaces. After adjusting the trigger, installing the reduced power spring set, and installing the Magpul MOE grip, I have a KILLER trigger that breaks at 4 lbs with zero creep, and has a short reset....all for a total of 50 dollars!
<br>I'm happy. This will be my go-to parts kit from here on out.

It just works.

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It's a cheap LPK that works perfectly well. Weight on the trigger is pretty good, a step up from mil-spec. Stainless trigger also looks super sharp on my AR pistol.

Best Buget Lower Parts Kit

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I have purchased a couple different brands of budget lower parts kits, and this is by far the best one. This was mounted on an Anderson lower and everything went together perfectly. No complaints so far.

Best Lower Parts Kit


Best lower kit of all I have used. Choose it when possible. Have created 12 different builds with this lower kit

Good item . . worth a try.

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Have used this kit in several builds and everything has fit great and has worked flawlessly so far. I have had no issues with this kit and the stainless trigger looks great with a black or a raw lower.

Best Mil-Spec-ish trigger group I've ever used


I love this LPK. I bought this kit because I was curious about the trigger and the hammer setup. The trigger is really nice with a crisp break and a short and very positive reset. I even like the bits that I didn't use in my last install, i.e. the bolt catch and the mag release and the safety. I will put those to use in my next beater rifle build. Overall super solid and I'm planning to get a few more of these the next time I see them on sale.


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All you wanna be gunsmiths on here whining about this lower parts kit have obviously not assembled as many lower receivers as you brag about. It’s easy to hide behind your keyboard and complain about the trigger pull, bolt catch button, poor coating, catch fail, pins won’t lineup, fits are too tight, fits are too lose, your mommy was at the grocery store, whatever. I’ve installed several of these particular parts kit and I can tell you right now this is a solid machined, nice functioning, excellent fit that works perfectly. Like everything else, you went to show off to your friends how awesome you are and couldn’t get it put together under the pressure of being watched which embarrassed you in front of your Xbox friends so you blamed the parts kit and stomped down to mommy’s basement to unleash the keyboard warrior within. Hahaha

Rough machining causing issue. Fix included.

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I ordered these parts for my first build. I gave them 2 stars because there was an issue with my trigger and hammer binding up together and now allowing the trigger to reset. This build was on an AR Pistol, so immediately I thought it was a gas, buffer, spring issue.
<br>After I found others with the same issue online, it was apparent the the parts I received were poorly machined. I have since made the repairs to my fire control group and all is functioning as intended.

a well kept secret lpk

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4.5 lbs out of the box...don't understand one review here that was dissatisfied....I am quite pleased and will buy more!!thanks PA!!

Best budget improved trigger group

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It's no Timney trigger, but you're not paying for one here either. Very happy with the small amount of creep and crisp break. Much better than competetor's similarly smoothed trigger group. ALSO, went through 600 rounds of both brass and steel in one session and no light primer strikes. Gobbled up whatever I fed it. Rest of kit worked as expected. Placed it on a pistol build so the agressive texture on the pistol grip was welcome.

Great trigger better price!


I am about to tell you something that may completely shock you. Anderson gets such a bad rap that it is amazing and that is ok by me since it keeps the price what I call FAIR. It is a trigger all of them if mil-spec is basically the same. Size, shape or form. Ask yourself what is different? the fact one may be polished better? This trigger has no slop and no grit and it's reset is just fine for a life or liberty rifle. If you pay close attention the rear of the hammer is bobbed. Not only that but they have machined out a wee bit more material there cutting you weight down even more. Less metal in that hammer allows for a faster spring. Anderson takes great pains in design and function and I have no gripes about my trigger in my L or L weapon. (Life or Liberty). Machining is spot on, the polishing is well done, and the weight cut is significant. Spend your money on a good quality bolt and barrel. Don't be so hung up on tacticool.

Fine, but missing parts.

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These are what we would call... the minimum acceptable parts. They work, they are in spec. However there is no noticable difference between this trigger and any other trigger, so if you're getting this one for the cool stainless trigger, you won't find any advantage, in fact this trigger is a bit worse than my factory New Frontier Armory parts kit. That being said that wouldn't matter much, and this would get more stars from me, however, my parts kit was missing the Bolt catch plunger.

Junk fire control group

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Junk fire control group, heavy gritty trigger pull and disconnect issues. installed 2 of these stainless kits on 2 different lowers and will be removing both. ive built several lowers, first time using Anderson LPK and will be last time.

Decent LPK but ONLY IF you know how to fix the Reset Issue.

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Yes, these triggers will not reset without some filing on the hammer. Google "anderson trigger reset" and you will find the fix. Basically there is a bump on the hammer where the disconnector catches that needs to be filed off and honed. Very easy to do, but it makes me wonder about Anderson QA. Other than that it's good quality and worth the effort for the price, which could be $40-50 if the reset issue was fixed. The only other thing I will add is the hammer spring is very stiff, difficult to install, which makes for a very hard trigger pull. I don't have a scale but my guess it's 10-12 lbs. I ordered some 29 cent standard hammer springs from PA which I expect will bring it down to normal trigger pull of 5-6 lbs. Maybe then I'll give it an extra star.

Good kit at a great price

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Great price and quick shipping by Primary. Good lpk kit, nothing missing went into Spikes lower with no problems. Trigger is heavy and gritty, but what can you expect for 29.99. Still a killer deal

think about it before you buy it.

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Take down pins badly discolored, trigger group sticks.

Good parts kit for the sale price

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Bought three kits on sale. All parts were there and fit nicely into Anderson lowers. In fact I got a few extra parts. Quality was fine. No problem with fit.
<br>I used Geissele triggers so I didn't use the stainless steel trigger groups that came with the kit. However, I temporarily installed one set just to see what they were like and didn't like the trigger. Gritty and heavy.

Good product but...


I liked the kit there was nothing wrong with it pretty standard. My only complaint is the parts kit was missing the hammer pin and trigger pin and now I can't finish my lower till I get new ones. I was happy though about the prompt shipping primary arms offer.

Great survice


It's my first build and my first ar the parts are great and wasn't expecting all of the parts to already be separated in color coded bags that really helped me out to figure what went where the only thing I've got an issue with but not a big one Is the trigger its kinda gritty but nothing a little emery cloth and elbow grease can't fix other than that great it arrived after 3 days and I ordered it on a holiday weekend (not counting Sunday of course) will definitely order more stuff for my build from them great job

Nay !!!


It's the worst LPK I ever purchased. Trigger pull is hard and VERY gritty. The finish on the bolt catch button was lightly coated and shows bare metal. For a few bucks more.... PSA is a much much better kit. I've used a lot of them and never had an issue. :) P.A. always has great services. Shipped and received LPK super fast. Only that now I'll have to purchase the fire control group from another manufacturer.