Bushmaster ACR: A Parts Thread

lerch641

lerch641

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I've gotten messages asking about particular parts, installs, etc that I'm using in my ACR, so I figured I'd start a proper thread to discuss the uniquely ACR parts. I've separated the individual parts into their own posts within this thread and hot linked. If anyone wants more detailed pictures or descriptions than I initially provide, let me know and I can go back and edit.

Let's start with the background; this is a Bushmaster ACR that came out of BFI Ilion NY. I bought it in 2020 as my AR15 alternative, and have been working on it since then. Let's break it down;

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•Templar Precision G1 Non-QD Lightweight Trunnion
•Templar Precision G2 Folding Charging Handle
•Templar Precision G1-556 Lower Receiver (w. Lightweight Trigger Box)
•Magpul PTS Long Handguard
•Kinetic Research Group ACR Precision Forend
•Magpul PRS2 Extended Rubber Buttpad
•Ferni Lab Drum & Ape (safety core and detent) and Radian Talon
 
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Templar Precision G1 Non-QD Lightweight Trunnion

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Templar Precision G1 Non-QD Lightweight Trunnion

This part replaces the QD trunnion on the receiver, with a threaded version to gain a fixed barrel.

Why? Well, there's reported issues with some QD trunnions regarding the ratchet loosening off during a course of fire (or not, just really worn out). This trunnion mounts the barrel in a similar fashion to a standard AR15 (using a barrel nut with outer thread) and negates the concern of losing/wandering zero.

Installation is straight forward:
1) remove barrel from receiver
2) remove bolts and drive out roll-pins holding trunnion to receiver
3) install new TP trunnion in place, using the same bolts and roll-pins
4) remove all hardware (muzzle device, gas block, piston guide) from barrel
5) exchange QD ring/lever with new TP barrel nut
6) reinstall all hardware from Step 4 on barrel
7) install barrel into trunnion and torque to 35-50 foot lbs
8) tighten retention screw underneath trunnion

Is it worth it? If you're not regularly swapping barrels at the range, yes. A little weight saving, a little tighter grouping, and still as easy to change the barrel as a regular AR15, should I need to.
 
Templar Precision G2 Folding Charging Handle

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Templar Precision G2 Folding Charging Handle

Most of this will also apply to the G1 model aswell. This replaces, specifically, the factory charging handle, and not the assembly inside the receiver.

G1 = V1 non-ambi assembly
G2 = V2 ambi assembly

Why? Preference, pure and simple. The standard charging handle isn't bad, but it does stick out and can be caught on gear. The TP charging handles fold flat along the receiver by spring, but are still easily caught and manipulated.

Installation (for G2, the G1 is easy enough to not need instructions):
1) remove bolt and spring from rifle
2) drive out roll pin from left or right ambi-charging handle and remove handle
3) slide assembly back to witness hole and turn receiver upside down to let index pin fall out
4) right side up; remove charging handle from assembly
5) install TP charging handle (left or right side) and line up index holes
6) reinstall index pin into assembly
7) once flush, slide assembly into forward position and reinstall bolt and spring

Is it worth it? If you want something lower profile than the factory charging handle, yes. It is one-sided, so if you prefer to have the handle on both sides this is something to skip.
 
Templar Precision G1-556 Lower Receiver w. Lightweight Trigger Box

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Templar Precision G1-556 Lower Receiver (w. Lightweight Trigger Box)

This replaces both the factory polymer lower receiver and trigger box, and allows use of any standard AR15 pistol grips and trigger guards. It does require most of the hardware from the factory lower, so don't expect to be slapping it on out of the box.

Why? The factory lower is limited with options for changing grips, and due to the construction, can develop slack between lower and upper through use. The TP lower aims to improve these points and more by giving the user the choice of grip and trigger guard they want, tightening up the interface between lower and upper, and also providing a flared magwell.

NOTE: the TP lower is designed to use V2 safety cores, so if you have the original V1 polymer safety, it is recommended to change it. The V1 safety can work, but it's not a great solution. I used my V1 safety in the lower for a short time before I could get the parts ordered to change (see later posts for that).

Installation (you will need to provide your choice of pistol grip and trigger guard);
1) disassemble lower receiver from upper and buttstock
2) remove safety and trigger box
3) remove magazine release; slide button left to right, drive out vertical roll pin
4) remove bolt catch; drive out horizontal roll pin from bottom of lever
5) remove front and rear take down pins (same process as an AR15); use a small pin to depress the detent and remove pin(s)
6) reverse Steps 3-5 and reinstall hardware into TP lower
7) swap trigger, pins, and safety detent from factory trigger to included TP lightweight trigger box
8) reinstall trigger box and safety into TP lower
9) install pistol grip and trigger guard (same process as an AR15)
10) reassemble TP lower with upper and buttstock

Is it worth it? Money aside, this is a fantastic upgrade. Dana really put in the work getting these refined. It lets you personalise your ACR to your liking, and takes out any slop that may have existed. The magwell is tighter on magazines, so previous issues of magazines shaking enough and releasing during a course of fire no longer occurs. As mentioned above; it is designed for the V2 (or similar) safety, so the V1 safety has to be modified to work.
 
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Magpul PTS Long Handguard

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Magpul PTS Long Handguard

An easy upgrade if you can find them. The Magpul long handguard is a component for the airsoft PTS Masada/ACR, and doesn't come with a heat shield. You can absolutely use it without a handguard and deal with a warm hand, or as I'll outline below, swap the heatshield over from the factory MOE handguard. When swapped, the heatshield won't be an exact fit, but it does cover over the gas block area to provide some relief.

Why? Because the standard handguard is pretty short if you have an 18.5" barrel to be NR. KRG makes a long MLOK handguard, but you might like the standard Magpul design. All in all, just a longer MOE handguard.

NOTE: There is a model of long handguard by airsoft maker A&K. This does not fit a real Bushmaster ACR.

Installation (assuming you have the standard MOE handguard);
1) remove MOE handguard from rifle
2) drill out rivet holding heat shield
3) rivet heat shield into PTS handguard
4) remove any accessories from MOE handguard and install on PTS handguard
5) install PTS handguard to rifle

Is it worth it? Do you have an 18.5" barrel and like the MOE handguard but wish it covered more of the barrel? Then yes.
If you're already using something else like KRG, MI, or RPM Tool, then not really.

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Magpul PRS2 Extended Rubber Buttpad

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Magpul PRS2 Extended Rubber Buttpad

This is by far the easiest part to find and install. It's not ACR specific being a regular Magpul PRS accessory, but most people just don't consider it.

Why? Because someone wants a longer LOP. That's it. It'll fit any factory ACR stock (folder, fixed, PRS).

Installation;
1) unscrew factory buttpad
2) install extended buttpad

Is it worth it? Absolutely. If you want a longer LOP or even just want a thicker pad. It doesn't change the function so you can still collapse the stock shorter if needed. Not to mention you can get it from most gunshops if they carry Magpul parts.
 
Ferni Lab Drum + Ape

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Ferni Lab Drum & Ape (safety core and detent) and Radian Talon

Of all the parts I've changed, this next portion definitely took the most polish and fitting. A necessary fix for myself as outlined in previous posts to replace the V1 safety with the TP lower. It replaces the safety detent that rides in the trigger box, and the safety core (with one that accepts Radian Talon safety levers). The end result is a customizable safety with 45° throw and a very clean "click" from Safe to Fire.

Why? Because not everyone has a metal core safety necessary to reliably use the TP (or Remdef) lower. Additionally, the Talon safety and 45° throw are desirable features for some, like myself.

Installation (have some method to polish/grind before starting like high grit sand paper and a Dremel):
1) remove factory safety
2) remove trigger box
3) lift and remove safety detent
4) test fit FL safety detent
• if it fits tight, polish interacting surfaces (of detent and trigger box) until detent snaps into low position without force
5) reinstall trigger box
6) test fit FL safety core
• if it fits tight, polish interacting surfaces until core fits and rotates without interruption
7) remove safety core and test fit safety levers
• if tight, file dovetail of safety core until lever can slide on and off without force
8) install safety core and install safety levers

Is it worth it? For the tactile feel and the 45° throw alone, I'd say yes. The customizable safety levers is just the cherry on top. It does take some fitting as mentioned, but it's easy enough to do myself. You can skip the detent and go for just the safety core, but I figured I was already ordering one, why not both?

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lerch641 said:
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Templar Precision G1 Non-QD Lightweight Trunnion

This part replaces the QD trunnion on the receiver, with a threaded version to gain a fixed barrel.

Why? Well, there's reported issues with some QD trunnions regarding the ratchet loosening off during a course of fire (or not, just really worn out). This trunnion mounts the barrel in a similar fashion to a standard AR15 (using a barrel nut with outer thread) and negates the concern of losing/wandering zero.

Installation is straight forward:
1) remove barrel from receiver
2) remove bolts and drive out roll-pins holding trunnion to receiver
3) install new TP trunnion in place, using the same bolts and roll-pins
4) remove all hardware (muzzle device, gas block, piston guide) from barrel
5) exchange QD ring/lever with new TP barrel nut
6) reinstall all hardware from Step 4 on barrel
7) install barrel into trunnion and torque to 35-50 foot lbs
8) tighten retention screw underneath trunnion

Is it worth it? If you're not regularly swapping barrels at the range, yes. A little weight saving, a little tighter grouping, and still as easy to change the barrel as a regular AR15, should I need to.
Click to expand...

This upgrade noticeably increased accuracy for me.
I'll try to get some match ammo and take some pics next time.
 
Kinetic Research Group ACR Precision Forend

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Kinetic Research Group (KRG) ACR Precision Forend

This is it. This is the longest handguard for the ACR.

The Good:
-M-LOK slots at 3, 6, and 9 o'clock, interspersed with MOE/L3 mounts that will fit your old Magpul MOE rails or KRG accessory rail/sling mount.
-Adds 6.75" to the top rail so the overall top rail length is 23.5".
-Enlarged cutout around gas port to allow adjustment via tool/bullet.

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The Bad:
-Discontinued, so it's expensive if you can find one
-This is not a rock solid handguard, as is. If you slap it on there will be some rattle, which is noticeable if you also remove the QD sling mounts from the receiver. An easy fix is to clamp the top rail; I have done this using Magpul picatinny sling mounts. The other solutions some have used is to shim the studs that interface at the front of the receiver, or to tap and drill the handguard to use the forward guide rail screws. All of these eliminate the QD feature.

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Installation is straight forward. Remove handguard, and swap. If you want to solidify the handguard, see above (The Bad).

Is it worth it? If you have an 18.5" or longer barrel that you don't change often (or at all), want to use M-LOK, AND find a deal: yes. If you don't care about the length: Midwest and RPM Tool have longer handguards that, while not as long, are still in production, and won't need to be solidified.
 
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