How hard is installing an LPK?

If you are accustomed to working with small parts, you should be fine.
If you are not accustomed to working with small parts, read the directions and keep everything clean and organized; you should be fine.

If you don't like dealing with small parts, you won't really like building this. You might really like shooting it though. I don't really think this type of assembly is a big deal. You might.

The hardest part is getting the roll pin for the bolt catch started. Everything else is pretty simple. Just make sure your springs are in the correct order. Its easy to find install them backwards. I'm sure there are tons of YouTube videos.

Work on a towel so if you drop something it doesn't bounce across the floor. It is not difficult at all.

LPK = Lower Parts Kit?

I've only done it once, and a friend "helped" me. Actually, I watched while he did most of the work. Like Robert said, get the correct roll pin punch, watch a YouTube video and you should be good to go.

LPK is simple. Roll pin punches make it even easier, especially re the disconnector.

The only thing that can be a pain (for me anyway) is installing the detent for the front takedown pin.
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The hardest part is getting the roll pin for the bolt catch started. Everything else is pretty simple ...

Click to expand...

Well, almost everything else is simple. Since there has already been a lot of warning about roll pins, it should be mentioned that pivot pin assembly (spring and detent) installation can be VERY frustrating. In fact, if you look on ar15.com at their document about lower receiver building, (link here), the pivot pin assembly section states, "This is perhaps the hardest part of the lower assembly ..."

They encourage using an installation tool. I have used the tool and have launched springs, so it still can be challenging. I also have installed it flawlessly (even without the tool) and it takes only a few seconds. Just be careful, go slowly, and have a way to catch the spring and detent just in case.

I really enjoy building lowers. Get the right tools, practice by building and un-building several times, take your time, and have fun.

Very simple process. The proper tools make it even easier. I haven't built one in 3 years but I could probably still do it from memory. If your lower doesn't have a built in trigger guard make sure you brace it properly against a block of wood before knocking in the drive pin. A mag-well block is nice to have and fairly cheap. Install the magazine catch, insert the mag-well block, and grip the block in a vise, then do the rest of the assembly. But if you don't have a vise or mag block it's still an easy process. I assembled my first lower in less than an hour with no special tools, not even pin punches.

All this advice above is good. If I can add one more, don't try to do it by starting and stopping a video; there are excellent pictorial online references of which I've linked a couple below. I have almost no mechanical ability but I am good about reading things BEFORE I attempt them. I've now built 5 AR15's and an AR10 lower without any special equipment except a brass hammer and punches and have not messed up a single one...otherwise a good set of needle nose pliers and some patience are all that are required. Believe me, if I can do it anyone can.

https://www.pewpewtactical.com/build-ar-15-lower-receiver/

http://www.thenewrifleman.com/how-to-build-a-lower-receiver/

One trick that I did learn over time was to use a small punch all the way through to hold the hammer assembly in place and then start the pin from the opposite side and follow the punch through.

Anyone can put a lower together. There's a guy on Youtube that goes by 50% Tactical. He only has one arm. He has a video that shows you that even a one arm Vet can build an AR..
An OOPS Kit is nice to have on hand because things do fly.
http://www.jsesurplus.com/jseoopsrepairkit.aspx
The bolt catch is really not that hard. Just use a small allen wrench to line it up. You insert the small end of the wench from the front to hold the bolt catch in place. As you tap in the roll pin, it will push the allen wrench out.
Most often the hammer spring is the one that people put in backward. This Pic. should keep you from putting it in wrong.


Another tip. the trigger and hammer pins are the same. There is a notch in the center and a notch closer to one side. It really doesn't matter which way you put the trigger pin in. For the hammer pin insert the smooth side of the pin first.

Very nice animated video on the CMMG site.

Russellc

THE #1 thing with roll pins is to slightly bevel the end. Use a grinder. Or, put it in a drill and use something like sandpaper.

TRUST ME!

First one, I didn't bevel. I banged and whacked. No go.

Beveled and it started right in.

assemble in a cardboard box sitting on a table. Make sure when your putting the trigger guard pin in to start it that the trigger guard is in place, or you'l break those tabs. Use duct tape to cover the receiver when you do the bolt stop pin. Look up the "hitch pin front pivot pin" method. I drilled a 1/8 hole in a 1/4 drill bit, and the front pin took less than 10 seconds using this method. Thats the one thats famous for flying, more than all the others combined. A 1/16 drill bit, or similar is good for lining up the trigger/disconector. It will be a very tight fit with the pins, but very loose with the bit. Push it all into place, put the drillbit in, and push the pin in while wiggling the parts. Drill bit keeps things close enough to get the pin through everything. I would recommend you read up on 2 minute trigger jobs before to see if thats something you interested in.

GunnyUSMC said:

Anyone can put a lower together. There's a guy on Youtube that goes by 50% Tactical. He only has one arm. He has a video that shows you that even a one arm Vet can build an AR..
An OOPS Kit is nice to have on hand because things do fly.
http://www.jsesurplus.com/jseoopsrepairkit.aspx
The bolt catch is really not that hard. Just use a small allen wrench to line it up. You insert the small end of the wench from the front to hold the bolt catch in place. As you tap in the roll pin, it will push the allen wrench out.
Most often the hammer spring is the one that people put in backward. This Pic. should keep you from putting it in wrong.
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Another tip. the trigger and hammer pins are the same. There is a notch in the center and a notch closer to one side. It really doesn't matter which way you put the trigger pin in. For the hammer pin insert the smooth side of the pin first.

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yep, spring alignment is easy to screw up, and it looks like everything will work when you do it wrong. The disconnector spring has to be installed fat side in the trigger (counterintuitive) or you can expect behavioral problems.

MtnCreek said:

LPK is simple. Roll pin punches make it even easier, especially re the disconnector.

The only thing that can be a pain (for me anyway) is installing the detent for the front takedown pin.
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This works well. The first time you do it, you may want to put a plastic bag around it though. When you displace the hitchpin with the permanent pin, that spring has more load than you'd expect, and if your not holding tight, can push you. At 2:28 you can see where the spring fights back. Its easy enough to overcome, but it never hurts to have something to catch it if it does jump

Overall I didn't have much issue putting my AR lower together. I did manage to launch the detent for the safety across my work shop 5 times. How I found it every single time to finish the build is well beyond me. This tool might be useful in helping build one though.

https://www.midwayusa.com/product/9...nt-and-roll-pin-installation-tool-ar-15-steel

I didn't have any special tools when I did mine, just normal punches screw drivers, pliers ect... I watched a couple videos before doing it. One of them the guy wrestled that front pivot pin in with his fingers and the other the guy had some fancy tool for doing it. I just pushed it in an held it down with a micro flathead screwdriver and put the pin in. It took 5 seconds.

It's all a matter of having the right tools and knowing what you're doing, in which case it's boringly easy. Even if you have the wrong tools and know what you're doing it's not that difficult, even if you're using screwdrivers for punches, so watch the youtube vids beforehand and take your time and you can't mess it up too badly.

I would suggest ordering a few spare detent springs and detents just in case. And when installing the front detent, make sure you position a box to catch it when it launches.

I am getting ready to build my fourth lower. Take your time and enjoy it. It's not too hard. Buy your upper fully assembled.

Here is a link to the Red & Black my youngest son built with very little help from me. If a 13 year old can do it, I don't think you will have any trouble.
https://www.thehighroad.org/index.php?threads/red-black-ar-build.824308/
Oh! if you launch and loose a spring or detent, just shoot me a PM and I'll send you a replacement.

I've probably done over 100 of them (worked in a gun shop, and in the military I repaired small arms). I think they are easy, but I struggled at the beginning. I'm sure there are youtube videos that explain it well. My suggestion is you do it under the supervision of someone who knows how- at least the first time. It is easy to lose or damage parts or scratch up the receiver if you aren't educated. on the process. I would do it in exchange for you buying lunch, for example- I think its easy and I like showing people how to do these type of things.

Assembling a Lower isn't hard, but there are a lot of pits a guy can fall into on the way.

I crossed over my 200th AR-15 build a couple years ago, and I've worked on or rebuilt over twice as many. I worked on my first when I was still in HS, apprenticing part time under a local gunsmith about 4x my senior... He used to say "Van has tricks." whenever he'd show me a technique for certain assembly jobs, whether it was how to use a slave pin for disconnector in an AR, or how to hold your tongue just right and remove a Ruger single action hammer without removing the trigger - that was 20yrs ago, AR's are a lot more popular and prevalent now than they were then... So I really don't remember struggling with any part of an AR assembly, simply because I had a good teacher who ACTUALLY KNEW HOW TO ASSEMBLE ONE, not just some buddy from work who owns an armourers wrench and watched a youtube video.

I've shared the list of tools I touch during a build on this site a few times, it might seem extensive to some, but every build I take on goes well, goes smoothly, goes quickly, and I don't break, damage, or lose parts. Since I'm usually working on AR's I do NOT own, I also don't have a lot of margin for error - people will be forgiving of a ding or a scratch when they mess it up themselves, less so when someone else does it to their new toy. Similarly, if a guy breaks his own part, they'll chalk it up to their own learning curve, and it's their sunk cost. When I'm working on someone else's rifle, if something goes awry, that's money out of my pocket to rectify someone else's toy. An example here - a colleague borrowed one of my "AR Tool Boxes" to build his own AR this summer. Mechanical Engineering degree, built his own water purification system for his hunting cabin, handy guy... But he hadn't used a 14" torque wrench which reads INCH pounds before. So he sends me a picture - he'd cracked the body of his Vortex scope mount. The "click" on the torque wrench was so easy, he thought it was just slack in the ratchet. So the bad news - it was a $130 mount, plus he'd had custom cerakoting done; it only cost $10 extra to throw in the scope mount when they did the rest of the rifle, but doing the REPLACEMENT mount again as a stand alone piece was $50... $190 mix up... If I'd done that to someone else's rifle, I'd be out the $190, whereas I don't even usually charge for optic mounting & boresight jobs! So I use all of the right tools to do the job right.

About 6-7yrs ago, I started doing one-on-one or small group (father/son, husband/wife, couple buddies, etc) "build and learn your AR" courses, where "students" come into my shop, and I walk them through building their own AR's on my tools, then once it's built, we do a crash course on safety, function, manipulation, and marksmanship (which is varied, depending upon their particular application for the AR). It stemmed from a rifle course I offer as well, "get to know your AR," but aimed at accessing folks who knew they wanted to build one, but don't know where to start. I work with people for days/weeks/months prior to get their parts together before we start. To make the course (meaning the 10-15hrs we spend together) more interesting and personable, with some students of a specific aptitude and personality, I'll take opportunities to challenge their mechanical aptitude and see if they can figure something out before I instruct it - like installing a mag catch & release button. With some more competent students, I'll simply hold up a shop towel in front of their lower as they take on the pivot detent, with others, I'll hover with my hands and shop towel right in front of the detent, curled and cupped, because I KNOW that thing is going to fly a couple of times before they get it stuck. With some LESS competent students, I'll use leather shields laid against the receiver any time the mallet comes out to set a roll pin... I had a guy crack the extension bridge on his lower in my shop while I was helping his son at another bench, he didn't have his castle nut backed far enough off when he installed his buffer tube, so he couldn't get the tube to thread on all of the way to meet the buffer retainer - not knowing well enough to simply back off the castle nut, he grabbed a tube wrench and cranked it hard against the lower - something had to give...

Only thing that I have to add is to wear safety glasses when you are dealing with springs and the like. If they cut loose, you don't know just where the parts might go. Less necessary if you wear glasses anyway.