Rock River Arms LAR-300 X-1 .300 AAC Blackout Rifle Review

Josejuan contacted Rock River Arms to review one of their left handed models in 300 Blackout. Unfortunately, at that time Rock River Arms did not offer a left handed model in 300 […]

Josejuan contacted Rock River Arms to review one of their left handed models in 300 Blackout. Unfortunately, at that time Rock River Arms did not offer a left handed model in 300 AAC Blackout. However, they sent the new right handed LAR-300 X-1 rifle in 300 AAC Blackout (model XBLK1751B) for a quick review.
Rock River Arms LAR-300 X-1 rifle review - case

Making a case for the LAR-300 X-1
We receive many products for review, but most come up short in presentation and packaging. Typically rifles arrive in a cardboard box with company markings and maybe some bubble wrap for protection. Rock River Arms sends their rifles in a nicely molded blue plastic gun case with Rock River Arms branding. Inside the box it has areas to fit the upper and lower separately. Instructions are included. This case is better than many pistol cases. It is a big upgrade over cardboard and allows the new owner a protective case to store and carry their new rifle. This was a clear first indication that RRA is devoted to quality and attention to detail.
*Editor’s note: It borders on comical the extent to which Josejuan was impressed with the RRA case. He REALLY wanted to keep the rifle, but it wasn’t in the budget. So, I expected him to keep the case and send back the rifle.

.Rock River Arms LAR-300 X-1 rifle review - Jeff shooting..But what about the Rock River Arms LAR-300 X-1 rifle?
The LAR-300 X-1 is a relatively new mid-high end addition to Rock River Arms AR15 lineup. The LAR-300 X-1 is not quite as exotic as some fully customized AR-15s, but not your average mass produced Big Box store AR either. It can be hard for a novice to spot the subtle differences that warrant the higher price tag on a premium AR15. Precision is a notable feature that can be rather hard to detect with the naked eye, yet is rather important when wringing performance and reliability out of the AR platform. When talking about $1500+ ARs, a higher level of precision in manufacturing should be evident in fit, finish and function. While we do not have a machine shop QA lab for detailed analysis, and only had a one RRA rifle to examine, we were impressed with above average fit and finish on the LAR-300 X-1 rifle.
The Rock River Arms LAR-300 X-1 in 300 AAC Blackout which was sent for our evaluation performed without problems using factory and factory remanufactured ammo. We tried several brands of magazines (USGI, HexMag, Pro Mag Roller Mag, RRA 20 round aluminum magazine), firing slow, fast 3 round bursts, and complete standard 30 round mag dumps without issues.
The rifle functioned well, with one FTF from the Pro Mag Roller Mag and no FTE issues across a range of ammunition types.

Rock River Arms LAR-300 X-1 rifle review - Defender Ammunition CompanyFull list of ammunition tested with the LAR-300 X-1:

  • Remington UMC 220 grain subsonic
  • Remington UMC 115 grain supersonic
  • Hornady 208 grain subsonic
  • Defender Ammunition Company 220 grain SMK HPBT subsonic
  • Defender Ammunition Company 150 grain SMK HPBT supersonic
  • Defender Ammunition Company 150 grain FMJ supersonic
  • G2 Research R.I.P. OUT 200 grain subsonic
  • Hand loaded Palmetto Projectiles 203gr polymer coated lead projectile over 9.4gr of Winchester 296

Rock River Arms LAR-300 X-1 rifle review - 300 BlackoutRRA LAR-300 X-1 XBLK1751B Series Specs

  • Chambered in 300 AAC Blackout
  • Forged upper and lower receiver
  • 18″ fluted Stainless Steel fluted, bead blasted, cryo treated heavy barrel in 1:8 twist
  • Low profile gas block
  • RRA two stage trigger with enlarged “winter” trigger guard
  • RRA Star Safety
  • RRA Beast Muzzle Brake
  • Hogue rubber pistol grip
  • RRA Operator telescoping stock
  • RRA TRO-XL extended free float rail hand guard
  • Length 36.5 inches
  • Weight 7.9 pounds

JJ_RRA_talk-006Muzzle brake
Recoil of the 300 Blackout round is on the light end to begin with, but the RRA Beast muzzle brake did an admirable job of reducing muzzle rise and felt recoil appreciably compared to the Radical Firearms 16″ upper with standard A2 flash hider that was the closest comparison in our test pool. The looks of the RRA Beast muzzle brake are rather aggressive with a series of sharp points along the forward periphery, which may not be everyone’s aesthetic cup of tea, but we thought it enhanced the looks of the LAR-300 X-1. The barrel is threaded in the standard 5/8-24 which is fairly standard for .30 cal muzzle brakes and silencers. So, swapping on a different muzzle device is pretty easy, if desired.


Rock River Arms LAR-300 X-1 rifle review - TRO XL handguardThe TRO-XL extended free float rail is one of the nicer modern AR handguards we have seen. Until you have cut your hand on a poorly made handguard with sharp edges it might be easy to overlook the little details, like how RRA rounded off any sharp edges on the TRO-XL handguard. We wish more manufactures would take the time to make their handguards more user friendly. While quad rail handguards were all the rage a few years ago, RRA has moved past that fad to the newer free floated, modular style handguard that allows additional rail sections (one long and 2 short included) or accessory mounts to be added or removed, as needed. Although, sadly, with extra rail sections attached the rifle no longer fit in the RRA supplied carrying case. The integrated full length top rail is the the only permanently attached rail, and it is generally the least likely rail section for the operator to snag their hand on. At 15.5 inches long and 18.2 ounces, the TRO-XL is not an minimalist handguard, nor is it exceedingly light. However, it felt nice in our hands and gave the LAR-300 X-1 a nice overall balance.


Rock River Arms LAR-300 X-1 rifle review - TRO XL handguardUnder the handguard is the centerpiece of the LAR-300 X-1, the 18″ fluted Stainless Steel Heavy Barrel (HBAR) with 1:8 twist rate. Many run of the mill AR15s the past few years have come with 1:9 twist barrels, which limit the weight of projectiles which can be reliably stabilized. Using a 1:8 barrel opens up the 70-80 grain bullets which are generally much more effective on medium sized game, like whitetail deer. The bead blasted finish was a neither too flashy or distracting and complimented that robust fluting. That is all nice, but what really caught our attention is that RRA Cryo treats the barrel on the LAR-300 X-1. Cryo treating is a tempering process that relieves internal stresses within the steel. The end result is that cryo treated barrels are generally more temperature stable, so they warp less as they heat and cool. The target customer for a $1500+ AR15 isn’t likely the casual shooter, but rather someone who is serious enough to have observed point of impact (POI) shifts as their rifle barrel heats up due to shooting multiple rounds without letting the barrel cool fully between shots. Cryo treated barrels should warp less, causing less POI shift, extending barrel life, and making them easier to clean. We found the barrel in our test LAR-300 X-1 to perform well, but due to unfortunate issues with the optics we installed for testing and the limited time we had the rifle, we were not able to do a detailed accuracy study.

Rock River Arms LAR-300 X-1 rifle review - TriggerTrigger

After our Big AR Trigger Test Review the minutia of trigger feel is one of the first things we notice. We have been spoiled by a string of sensational AR triggers, and we know it. This set the bar rather high for the Rock River Arms two-stage trigger in the LAR-300 X-1. Not being a huge fan of 2 stage triggers in AR platform rifles put the LAR-300 X-1 at a bit of a disadvantage for this review, but we will evaluate how it worked more than the choice of single vs 2 stage trigger. As 2-stage triggers go, the RRA trigger is very consistent and predictable. That is rather high praise for an AR fire control group. Here is how Jeff described the LAR-300 X-1’s two stage trigger at the range:

“That is a neat trigger. It has got a little hump that you have to get over… it is almost like a false wall. Once you get past the hump to the wall, it is rather solid… then nothing (very light, crisp break).”

Rock River Arms LAR-300 X-1 rifle review - hogue pistol gripPistol grip
Having loved the feel of Hogue overmolded grips on pretty much any pistol or rifle, it should come as no surprise that the Hogue pistol grip was a big hit with our testing team. For shooters with average sized hands, this grip is fantastic. If you have big hands, then you might want to swap in the version of the Hogue grip that has an integrated beaver tail (link), to move the shooters hand slightly further from the trigger.

The RRA Operator telescoping stock is a nice upgrade from the standard carbine stock found on many budget AR platform rifles. The top of the RRA Operator telescoping stock is slanted, narrow at the top, wider below, to give a nice slanted surface for cheek weld. It is the same on either side, so Rock River Arms LAR-300 X-1 rifle review - stockequally useful for right or left handed shooters. A ribbed rubber butt pad helps a bit with recoil dissipation, although that isn’t a big issue with a 300 Blackout rifle. Hidden under the cheek weld swells on the side and behind the butt pad are two water tight storage tubes. I used to think such storage areas were silly, but with the explosion of battery powered optics, that space seems pretty valuable. There are Quick Disconnect fittings forward and aft, so the operator can choose where to attach a sling. Lastly, the stock is adjustable for length of pull, with a simple squeeze lever on the bottom leading edge to disengage the lock and allow adjustment. Overall, not a radically different AR stock, but one of the more comfortable and useful stocks we have used.

Rock River Arms LAR-300 X-1 rifle review - star safety selectorSafety selector

The RRA Star Safety Selector is very similar to a standard safety selector, but with a bit taller and more aggressively patterned contact area to allow a better purchase on the lever. It is set up for a right handed shooter. Would be nice to see an ambi safety selector installed to better accommodate lefties, although most folks would not need it.

Function with Subsonic 300 AAC Blackout ammo

As good as the LAR-300 X-1 shot with supersonic ammo, we had a bit of struggle when we tried our custom loaded subsonic ammo. Our custom loads (203gr polymer coated lead projectile over 9.4gr of Winchester 296) worked fine in the other 300 AAC Blackout ARs in our test pool, but would not fully cycle the Rock River Arms LAR-300 X-1. Our custom subsonic load did, in fact, chamber, fire and expel the spent case, but would not push the BCG back enough to strip a new round from the magazine and feed it into the chamber. Effectively rendering the LAR-300 X-1 a bolt action. Given that the 300 AAC Blackout round was designed with suppressed shooting in mind, we would have liked to see an adjustable gas block on this build so that the end user could tune the rifle to whatever ammunition was being used.

We planned to test the LAR-300 X-1 with our AFT Form 1 silencer build with parts from SD Tactical Arms. However, the Form 1 was not approved until shortly after the RRA rifle was sent back. Given what we have seen while shooting the Radical Firearms 16″ AR in 300 BLK with the SDTA can, it is likely that the increased back pressure created by the silencer would have solved the short cycling problem in the LAR-300 X-1.

Josejuan singing the praises of the Rock River Arms LAR-300 X-1 rifle

Josejuan singing the praises of the RRA

The LAR-300 X-1 rifle in 300 AAC Blackout has a lot to like. Advertised as a 1 MOA rifle at 100 yards, we found accuracy to be consistent with expectations using a wide range of ammunition. The fit and finish of the LAR-300 X-1 were above average all around, including a wiggle-free mating of the forged upper and lower receivers… which is often overlooked by AR manufacturers. Little touches like an expanded trigger guard to allow easy use with a gloved trigger finger and inclusion of RRA’s own Beast muzzle brake show that this is not your every-day AR-15. Built around a high-end SS barrel that is cryo treated, our results suggest that the LAR-300 X-1 was built for those who expect more. This is not a “budget” AR, nor is it a $5k 3-Gun open class rig. It is a nice step or three up from your average AR-15.

Gear Score
The RRA LAR-300 X-1 is a solid mid-upper spec AR that offers good value to the shooter that wants more than can be expected from a Big Box store's AR-15 rack.

Where’d you get that ammo, bro?

We are fortunate to have an arrangement with Defender Ammunition Company and Ammunition Supply Company where they provide some of the ammunition for our reviews. In return, we share our videos and reviews for use on their websites.

Rock River Arms LAR-300 X-1 rifle review - Defender Ammunition Company 300 BLK


Gallery of Rock River Arms LAR-300 X-1 images:

About JJ

A long time friend of, and frequent behind-the-scenes instigator…I mean contributor, JJ joined the Gear Report team in 2014 in a more formal capacity. Expect to see JJ’s ongoing contributions to reviews, while he coordinates with manufacturers and retailers to review their products.

If you want to see what it takes to make the cut here at Gear Report, look no further than JJ. Part inventor, part outdoorsman, JJ brings a wealth of experience to the Gear Report team, as well as some fancy book learning. A Structural Designer by day, JJ spends his nights and weekends on a massively broad range of outdoor and active interests. Whether making hunting knives, bamboo frame canoes, hunting platforms or various other creations, or hunting, fishing, paddling, boating, teaching martial arts, or re-engineering ammunition reloading equipment, JJ is always up to something interesting. Usually several somethings.

A native of Guatemala, JJ brings a valuable different perspective to Gear Report. We will see if we can get him to add some Spanish language content to the site, as the need for fair, trusted information on outdoor gear is not limited to English speaking readers.