1. Rear Takedown Pin Not Fitting Tool
2. Rear Takedown Pin Loose

JP Lower With Trigger: $299

Rear Takedown Pin Not Fitting Tool

Installed on a forged aero precision lower and m4e1 aero upper.install was very simple, fit and finish is top notch. I have the hogue freedom fighter magazine lock kit installed. The rear take down pin works perfectly raising the upper just enough disengage mag lock pin. I'm definitely purchasing more of. Anyway work the pin in and out until you start earing off the coating to locate the wear point, then check the take down pin hole ID on both sides, then pull it dimension up from the bottom or top measuring both top and bottom locations of the holes, if they are consecutive do not ouch your lower at this point. Great finish! AERO PRECISION M5.308 TAKEDOWN PIN. Posted by Royland on 14th Sep 2019 No fitment or function issues. Never had to look elsewhere for all. I was test-fitting the receiver and block and noticed the pins that came with the block only fit the takedown hole at rear of the receiver and not the front pivot hole. Are the takedown and pivot pins (in a lower kit) the same size or do I need to modify one of the receiver block pins to match the pivot hole?

1. Hard coat anodized JP-15 forged lower
2. Professional gunsmith installation
3. Safety
4. Anti-Walk Pins
5. Trigger
6. Disconnector
7. Speed Hammer
8. Complete spring set

Their Modular Trigger: Up to $350+

1. 'one size fits all' trigger module

In the past, JP has designed and marketed a high quality single-stage module as part of our ongoing pursuit of improvements to the AR-15 platform. We knew we had the best single-stage trigger available but needed a fool proof way to enable the customer to install it. So, we ended up following the trend with our own drop-in modular trigger.

Experience is a valuable teacher, and we’ve been in this game longer than most. In the end, we came to the realization that there are simply some significant limitations to the modular trigger concept.

Unlike other firearms that were designed from the ground up to incorporate modular fire control packs, the AR-15 and AR-10 platforms were never designed to work with such modules. The possible runout in trigger/hammer pin hole locations and safety selector position on receivers made by countless manufacturers can cause potential compatibility and even safety concerns.

The module always represented a compromise in many respects. It needed to be manufactured to adequately fit and function in a wide variety of lowers compromising with the peculiarities of each, but “adequate” and “compromising” are not words we use here at JP. We and our customers have always set the elevation of our sights a number of clicks higher, and we feel that most modules are not suitable for anything other than recreational or non-critical competition applications where proper function is a luxury rather than a necessity. Moreover, modules simply do not have an extended track record for reliability, and many have been recalled for reliability or safety issues.

We very seldom talk about “cost” here at JP; we talk about value. We are generally not the most or least expensive, but we are almost always the best value for your dollar. With the modules inherent compromises and the $300 price tag, we had to come up with a value-based solution.

So here it is: we are offering one of our JP-15 lower receivers as the module with the complete installation of either our Competition or Tactical Fire Control System. JP will factory install a JP fire control kit into a genuine JP-15 forged lower receiver for almost the same price as the competition’s modular trigger alone.

1. DIY AR-15 Build: Buttstock Installation

Today in part eight of our DIY AR-15 Build we’ll be showing you how to install the final part onto your Lower Receiver, the Buttstock.

While we say Buttstock, this step is comprised of quite a few different parts that aren’t in the standard Lower Parts Kit, like the one we recommend from Stag Arms.

This isn’t the place to skimp on quality parts and doing so will cause unnecessary problems that could have been avoided in the first place, namely the Buffer and Action Spring. Believe it or not these are some of the most important pieces of the entire Lower Receiver and are the cause of many puzzling AR-15 issues.

Continue reading for our step-by-step instructions for installing the Buttstock with detailed photos and video.

Buttstock Installation

Before we get into the actual steps of installation, let’s talk a bit about the selections we’ve made on parts here and why we recommend them.

Mil-Spec Receiver Extension (buffer tube)

Commonly referred to as the buffer tube, Receiver Extensions are available in a Mil-Spec or Commercial version. The differences are typically that the Commercial tube is made from extruded aluminum rather than forged aluminum like the stronger Mil-Spec tube. The two differ in size as well and you’ll find more aftermarket stocks built for the Mil-Spec tube.

As a rule of thumb here, inquire about the manufacturing process of your Receiver Extension, as there are instances of extruded Mil-Spec diameter extensions being sold out there.

Why Stake?

Something we’ll get into with the installation video is staking the Receiver End Plate and Castle Nut. This is done to ensure the Castle Nut doesn’t work free and allow your Receiver Extension to turn. If allowed to turn, the buffer retainer could release causing a headache and leaving you with a non-functioning firearm.

Staking is the process of pushing the metal from the Receiver Endplate (Sling Plate) into the staking slots on the Castle Nut. Four of them are available and optimally you should at least try to stake in two spots if possible. With many of the newer sling plates and their flared orientation, you may not be able to get more than one spot staked. That was the case with our IKICKHIPPIES SLAP Plate as well as the Magpul ASAP we’ve got on another build.

If you plan on switching out your endplates and experimenting to find the one you like best, you can utilize blue Loctite (non-permanent) on your Castle Nut after tightening or torquing it down (specs below). The Castle Nut is also a great place to add a witness mark, particularly if you leave it unstaked.

Buffer Differences

With this build we’re using a Bravo Company H (Heavy) Carbine Buffer, which is weighted with 1 Tungsten and 2 Steel weights. As your gas tube is shortened (From Rifle Length to Mid-Length to Carbine Length) it becomes more important to utilize a heavier buffer to regulate the added pressure pushed into the Bolt Carrier Group by a Direct Impingement system like we’re building here.

The heavier buffer absorbs the added pressure, as well as partially delaying the “unlocking” phase in the cycle of operations. This delay can help with early/hard extraction problems which occur when the bullet hasn’t departed the barrel and there’s still built up pressure in the cartridge case.

Piston guns also tend to run better with an H buffer to mitigate their inherent hard extraction due to the close proximity of the piston to the gas port. Heavier buffers can also help to control bolt bounce, which is the bounce that occurs when the Bolt Carrier Group returns after making contact with the Receiver Extension.

Rear Takedown Pin Loose

Utilizing an H Buffer in this build is also a test for us, as you’re never going to truly know how everything in a build functions until you get out and shoot it. One last thing to mention here is that underpowered ammunition in combination with a heavier buffer may cause malfunctions. We’ll be testing that too though.

Action Springs

Commonly known as a Buffer Spring, the Action Spring is an often neglected and tremendously important part in maintaining a properly cycling AR-15.

A Carbine Action Spring, like we’re using with this build should be between 10 1/16 in. and 11 1/4 in. If it falls outside of these parameters it should be replaced, this is it’s go/no-go measurement. On a rifle length spring the go/no-go changes to 11 3/4 in. to 13 1/2 in.

Parts Needed

• Magpul MOE Stock (Mil-Spec Model)
• — The following parts are in the Stag Arms Lower Parts Kit —
• Buffer Retainer
• Buffer Retainer Spring
• Rear Takedown Pin
• Takedown Pin Detent
• Takedown Pin Detent Spring

Tools Needed

Assembly Instructions

• Thread the Castle Nut onto the Receiver Extension Tube with the Cuts facing aft.
• Place the Receiver End Plate, in this case a SLAP plate, on the Receiver Extension with the raised area facing forward.
• Thread the Receiver Extension Tube through the back of the Lower Receiver, stop just before the Buffer Retainer hole.
• Insert the Buffer Retainer Spring and Buffer Retainer into the hole and depress the corner of the retainer with your index finger.
• Hold it down while continuing to screw in the Receiver Extension Tube until the Buffer Retainer is trapped down by the tube.
• Insert the Rear Takedown Pin halfway in the hole from the starboard side. Ensure that the cut in the pin is facing aft.
• Place the Takedown Pin Detent into the hole in the back of the Lower Receiver, followed by the spring.
• Move the Receiver End Plate into position to set just on top of the Takedown Pin Spring. Press it against the spring, being careful not to bend the spring.
• Screw down the Castle Nut to lock the spring in place and tighten with your buttstock tool to the proper torque of 40 ft. lbs. or just make it tight!
• Alternatively you can use Blue Loctite (not Red!) to ensure your Castle Nut doesn’t come free or stake it.
• To stake the Castle Nut, take your Center Punch and drive some of the material from the Receiver End Plate into the pre-cut areas in the Castle Nut. Optimally you want at least two areas staked, but when using some end plates you may have just the top area to stake. This was the case with the SLAP Plate and also the Magpul ASAP we’ve used in the past.
• It’s also a good idea to make a Witness Mark so you visually know if the Castle Nut is coming loose on you.
• Insert the Action Spring and Buffer into the Receiver Extension Tube and finish the Lower up by installing the Magpul MOE Buttstock on to the Receiver Extension Tube.
• This is done by pulling the release lever pin straight down to get it all the way on. It’s a pain in the butt on the Magpul MOE, as most collapsible buttstocks simply require you to pull town on the release lever.

That completes the Lower Receiver portion of this DIY AR-15 Build. Join us back here soon for our first installment in the Upper Receiver Assembly!

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