I have decided to upgrade some features on my Ruger SR-762. Upon initial release there were some complaints about this rifle. Mainly about the trigger, and some difficulty with the provided magazines (Magpul Gen2). Since its release Ruger has addressed these concerns by; upgrading the trigger with the Ruger Elite 452 AR-Trigger (this trigger is a two-stage trigger with a 4.5 pound trigger pull), and now provides Magpul Gen3 20 round mags (I haven’t had any issues here). Other included upgrades/items included: grip, flash suppressor, stock, 3x 20 round Magpul Gen3 mags, case, 2x Picatinny rail attachments (about 3” long), adaptable handguard, and removable iron sites (there is more, but this is more about the install).

I decided to upgrade my stock from a Magpul MOE SL, to a Magpul UBR (Utility/ Battle Rifle) for a couple of reasons. First, and most importantly, I couldn’t get a good cheek wield with the MOE SL (at least not where I am accustom to). Secondly, I wanted to reduce the kick to help me get the second round off more accurately. I don’t know if I mentioned this before, but the SR-762 is a 7.62x51mm (.308) and kicks quite a bit harder than its little brother, the 5.56mm (.223). Finally, because the UBR looks way cooler than the MOE SL.

These instructions will work with most AR platforms (its doesn’t have to be my rifle), however there are some specific considerations when placing this on a 7.62 versus a 5.56 (I will do my best to highlight these differences).

#1 Clear your weapon. Don’t be that asshole who gives gun owners a bad name by blasting a round through your garage into your neighbor’s house. Seriously, don’t be that guy.

#2 Remove your upper receiver from your lower, and place it somewhere safe.

Magpul UBR Stock Install
Upper receiver has been removed.

#3 Remove your buffer, and buffer spring from your buffer tube. No need to get smacked in the face by a piece of metal under tension from a spring.

#4 Remove the old stock. Specifically for the MOE SL you need to get a tool into the release mechanism so you can pin it open and allow it to slide off the Buffer Tube. If you get stuck here just YouTube your specific model.

Magpul UBR Stock Install
This is the part I had to pin open on mine (yours may be different).

#5A Brace the lower receiver in such a way where you can manipulate the buffer tube (two-handed) unobstructed. Using an AR armors tool (or well padded pump pliers—not the best option) loosen the castle nut.

#5B Now this is important. Reach into the lower receiver, just in front of the buffer tube and depress the buffer retaining pin (tiny pin under pressure by a spring). Keep positive control on this pin and loosen the buffer tube just enough to remove the pin. Or, like me, you can completely forget about this pin and watch in horror as it shoots clear of your rifle. With the pin removed you should now keep positive control on the end plate because there is another pin we need to be concerned about (takedown pin spring and detent). Place both springs and pins somewhere safe.

Magpul UBR Stock Install
Buffer retaining pin/sprin (left), takedown spring/detent (right).

#6 Install the new buffer tube. Make sure the buffer retaining pin and spring are properly placed inside the lower receiver. At this point I separated the UBR into two pieces.

Magpul UBR Stock Install
UBR separated, upper (top), lower (middle), buffer tube (bottom).

#7 Place the upper portion of the UBR over the buffer tube (its obvious, just slide it on). Before you get it completely seated make sure the takedown pin spring and detent are correctly in place. Secure the upper UBR section to the new buffer tube via the provided hardware (screw).

Magpul UBR Stock Install
You don’t want the takedown spring bent, it should be flush. Take your time.

#8 Attach the UBR lower portion using the release latch. This shouldn’t be hard, if you are forcing the two pieces together, stop and reevaluate.

Magpul UBR Stock Install
Look at the mechanism while putting the two pieces back together.

#9 Install the buffer and buffer spring. For the Ruger SD-762 I had to purchase a new buffer/Spring to accommodate this stock. Specifically, the CAR-10 from heavybuffers.com, as recommended by the customer support staff at Magpul. If you don’t know whether you need an upgrade, call the Magpul customer support.

Magpul UBR Stock Install
Buffer/spring that came with my Ruger SR-762 (top), new buffer/spring (CAR-10) I acquired from heavybuffers.com (bottom)

With the last step complete, you should now have your new Magpul UBR stock installed. I decided to take it a little farther. I removed the storage compartment for a cleaner look (I didn’t plan on storing anything there), and I added a larger buttpad. Finally I adjusted the preset screw to my specifications (this feature allows a quick deployment to your favorite setting).

Magpul UBR Stock Install
Before I took it a step farther.
Magpul UBR Stock Install
After I took it a step farther.

Specifications (courtesy of magpul.com)

UBR Collapsible Stock

  • Weight: 23.5 oz.
  • Weight, w/Entry Receiver Extension: 26.1 oz.
  • Length, Stock: 8.0-11.4 in.
  • LOP Adjustment: 7-Position (0.56″/position)
  • LOP Adjustment Range: 3.4 in.
  • LOP, M4 Collapsed: ~11.1 in.
  • LOP, M4 Extended: ~14.5 in.

If you have any questions about this install please feel free to ask in the comment section below. I also plan on writing about other upgrades on this platform.