Lower parts kits experience, what's your favorite?

[jurassic]

I recently used a Rock River Arms LPK and found it to be much better than the DPMS and PSA I have used. They all work, but the RRA has true roll pins which slide right in compared with the folded type pins in the others. I also noticed the safety action to be crisper and have better action. I'm guessing it's because the safety and spring follower work together better (machine work or tolerance?). I know the DPMS felt kind of mushy and did not have a positive feel to it. I also noticed the right side of the safety had a machined indicator grove instead of a small stamp. The DPMS pins fit way too tight and care must be used installing them with proper tools no less.

The PSA kit was a complete lower build kit with buffer tube and M4 style collapsible stock. The grip did not fit the receiver well at all (grip with DPMS and RRA were good,) it looked like the top of the grip that slides on the receiver was spread open, very loose. The extension looked and fit ok, but the inside of the tube was not smooth at all it felt like the tooling left behind a bunch of rolling hills. The stock did fit very well, but the part you squeeze to slide the stock was loose.

I left the PSA LPK in the bag and will send the whole thing back.

I just wanted to share my experiences since so many people ask about the differences and want to know why the differences in prices.

[LRRPF52]

For reliability and QC procedures, Colt small parts are at the top, but not sold in kits that I've seen.

I would rate the Daniel Defense LPK's as one of the top kits on the market.

Keep in mind that these small parts are made by specialty niche sections of the industry, where one only does springs and maybe roll pins, while another does Metal Injection Molding (MIM)for magazine catches, bolt catches, hammers and triggers, and another does case-hardening. Another will do detents, pins, and plungers, with another doing selectors and disconnectors.

The plastic, glass nylon, zytel, and such are an entirely different market segment.

With the Rock River-branded parts, they have good triggers, hammers, and other components, except for the detents, which are sourced from a corner-cutting practice in the AR15 industry that saves money by zinc-plating them, rather than cadmium-plating like the Mil-spec Technical Data Package calls for. I learned the hard way that lower parts are nowhere near the same when running high-volume courses in extreme cold weather, and my pistol grip fragmented, exposing zinc-plated detents that were corroding in real-time before my eyes, as in chemical reactions visibly reacting on the selector detent surface.

None of the companies packaging the parts together are the manufacturers, due to the depth and width of manufacturing capacity that would be required to support such an operation, so like with AR15's, brand names mean the final assembly warehouse.

There are also a lot of parts being imported from the Philippines for the AR15, to include bolt carriers, barrel extensions, upper receivers (with no forge code), all the lower parts, etc.

If you want to get an education in lower parts kits, break down a Colt SP-1, Sporter II, 6920, and then any modern vismod AR15 and compare them. The differences are quite pronounced, starting with the fact that the components from a Colt have proof and QC inspection stamps on them, and there are dimensional and design differences as well.

[melensdad]

I've built/help build probably 100 AR15s and the one brand that I hate to use, in fact I refuse to use it, is DPMS. Their quality control can be summed up in one word: SUCKS.

[aclark]

I used RR in my first build and everything fit nicely and runs well. I used a PSA on my current build with Ergo grip and no fire control group. Pins are ok and most fit well. Had a few problems getting the bolt catch pin and trigger guard pin in. Not sure if it was the pins or the lower. Lower was PSA as well.

[Drifter]

Colt

http://www.brownells.com/rifle-parts/receiver-amp-action-parts/parts-kits/colt-lower-receiver-parts-kit-prod27064.aspx

If Brownells is out-of-stock on the complete kit, they sell Colt parts individually as well.

[CPT.CRAZY]

I have used dpms and kits from J&T dist.(double star) I have had great luck with the J&T's. Not the best triggers but they usually get swapped out for something else anyway.

[montana]

I have built many rifles for multi gun match shooters and have used DPMS, stag arms ,Colt and some others with mysterious birth places. Like all mechanical items quality cost more money but will most shooters need the same high end parts? One rather wealthy shooter purchased a JP custom rifle and had it fail completely at a match and sold it cheap to me. He was convinced it was junk and wouldn't listen to any thing I would say to change his opinion. At the next practice session he watched me shoot it without any failures and begged me to sell it back to him which I did after a lot of teasing. All I did was replaced a defective gas block and adjusted for the ammo type. Sometimes opinions are made without real understanding of the problem. I have had some problems with the detents ends breaking off probably for the reason LRRPF52 has stated , but it was an easy fix.. Receivers, barrels ,and receiver extension tubes are always the most important starting point for my rifle builds. I have seen DPMS, Stag arms rifles run for a long time without any issues what so ever. I view my firearm builds like a vehicle purchase, the longer the vehicle runs with the lowest cost per mile is the winner. High end doesn't always mean the best value. If one is planning for pure combat and the end of the world, then by all means don't skimp on parts and buy the best parts like Colt . DD, or any other proven top end part.

[LRRPF52]

One thing that will help you when installing the trigger guard roll pin is to bevel the edge of it before attempting to drive it in with your punch and hammer.

It also helps to support the lower receiver with a backstop so that your line of work is perpendicular to the bench surface, so I have wooden blocks that I use to position the lower flat to the work space.

Using a grinder on the roll pin will help you put a nice angle on it, so it starts right away into the hole. I've done them like this for the past 11 years, and it's night and day different than just trying to force the roll pin into the trigger guard ear, which many builders have broken off when pounding away on their lowers.

Speaking of receiver extension tubes, all are not created equal. The Colt, DD, and VLTOR tubes are forged units, whereas a lot of vismod parts out on the market are machined, welded, brushed, and anodized to look like one-piece. Even the M110 SASS has been shown to blow out the rear of the extension tube, so sourcing your parts is a more complex process than one would think.

I know that AA only uses forged extension tubes for carbines.

[tx4guns]

From best to worst that I've used...

RRA
DoubleStar
Spikes



DPMS. Hate them.