Miller Precision Arms MPA300 Guardian


Miller Precision Arms was showing off their MPA300 Guardian at the SHOT Show Media Day this year.  According to MPA, the Guardian is the first, “and only”, .300 Win Mag to reach the market in a truly AR platform.  The show model was set out in a nice personalized hard cover rifle case, complete with extra magazines and accessories, enticing shooters to get behind the cross hairs.

Made from 7075-T651 aircraft grade aluminum, the MPA300 is tailored for the serious precision shooter.  MPA boasts the Guardian is designed to weigh the same as the M110 sniper rifle, but yield twice the range.  The MPA300 uses a titanium charging handle, and firing pin.  Only premium barrels from Kreiger, Bartlein, and Mike Rock are used in MPA rifles, and they are contoured in house using CNC machines.  Barrels are chambered using Benchrest building techniques assuring the hand cut chamber is perfectly aligned to the bore.  With only a few exceptions, the MPA300 has all AR10 internals making any replacements easily obtainable.  Externally, the Guardian is ready to accept aftermarket components, such as the Magpul PRS 7.62×51.

Miller Precision MPA300

The semi-auto AR platform, using double stack magazines, delivers amazing results that should quell most of the concerns any skeptic might have.  Despite a continuous strong debate on the accuracy of semi-auto precision rifles versus traditional bolt-action rifles, in my opinion, the MPA300 joins a short list of semi-auto rifles that could go the distance with the best.

MPA300 rifle

The MPA representative had me firing at a 565 meter steel target.  Obviously the rifle was dialed in for that distance, but even with sometimes brisk cross winds I was able to get on target after a near miss on the first shot.  From a bench rest position getting back on target was almost immediate after each shot, despite the powerful 300 Win Mag cartridge being fired.

Recoil was amazingly reasonable, as I was fully expecting a much harsher welcome from the Guardian.  In comparison, the MPA300 recoil was equivalent, and perhaps even just a bit lighter than the .308 GA Precision “Rock” Remington 700 I routinely shoot.  This coming from a rifle with a 20” barrel.  Other than feeling the bolt cycling, the Guardian’s tolerances were very tight.

Miller Precision MPA300 rifle

The MPA representative advised that they are building the MPA300 to be capable of accurate shots to 1500 yards.  From what I got to experience, the Guardian seems to be a serious contender in precision rifles, and a stand out semi-auto option.  Perhaps the only drawback is the Guardian’s price, set for $5399.  I guess when you’re the only one on the market the price can reflect your solitude.  MPA must recognize the price line is steep, however, as they offer a financing option when purchasing.

Miller MPA300

Here are the MPA300 specifications:

  • Barrel Material – stainless steel ultra match; chrome-moly steel optional
  • Barrel Length – 20” standard; 16.25”, 18”, 22” and 24” optional
  • Contour – SPR standard; Super Match, Match, M4, and Bull Barrel optional
  • Caliber – .300 Win Mag
  • Gas System – Rifle length standard; Pistol, Carbine, and Mid-length optional
  • Forearm – Precision Reflex Inc. 308 AR Delta standard; YHM 12.520” and 12.520” Customizable, and Precision Reflex Inc. GEN III Carbon Fiber Delta optional.
  • Stock – Magpul PRS 7.62×51 standard; LMT SOPMOD optional
  • Finish – Cerakote Dark Earth (Other color options available); Parkerized, Blued, Bead Blasted, Polished, Custom, and Hard Black Anodized
  • Thread Pitch – 5/8-24 tpi standard; 1/2-28 tpi, 9/16-24 tpi optional
  • Twist Rate – 1:10
  • Muzzle Break – Hammer Head
  • Trigger – 2-stage standard; Giesselle National Match 2-stage trigger option

By Aaron

Aaron is a sergeant with a midwestern police department, where he serves as a trainer, supervisor and SWAT sniper. In addition to his broad tactical knowledge, Aaron is an experienced hunter using bow and both modern and blackpowder firearms.

9 replies on “Miller Precision Arms MPA300 Guardian”

Yeah, what’s up with that? The NEMO Omen is a 300win chambered AR and it was at the 2013 SHOT Show.

I agree! I wrote an article on the NEMO when they debuted at NRA 2012. However, to be fair, the Nemo Omen (their .300 Win Mag rifle) is slightly different, and I think MPA is playing up that difference for marketability.

The Omen does not have the traditional AR style charging handle, and instead incorporates a handle that is directly connected to the front side of the exposed bolt, similar to some belt fed weapons. The Omen is charged by grasping that handle to pull the bolt back.

This type of bolt system requires a slightly modified upper receiver as the handle must enter a groove as it cycles or locks in the open position.

Although fairly minor, I guess a purist could say that the MPA is the first “truly” AR platform. I’ve attached a YouTube video that gives some good close-ups of the Nemo difference.

Thanks for reading and posting.

I too was going to point out the Nemo Arms Omen. I think that MPA needs to do their homework. Side charging handle kits are commercially available for mil-spec ARs (look at JP Enterprises, etc.) And let’s face it nothing (the possible exception is the trigger group) on a 300 WinMag AR is going to be mil-spec to begin with. The Nemo is clearly an AR operating system and MPA is playing word games claiming they are the first to the market with it.
Thanks for the first hand look at SHOT products.

Am I the only one who feels that having a dust cover protecting the BCG is extremely important?

I would agree completely KO. Any AR-style rifle that is going to be used in a military, LE, or hunting situation needs to have the BCG protected during non-firing situations.

I suppose someone who is just a target shooter may not have the same concerns over dust/dirt exposure, but in general the cover is a good part to have.

Everyone plays word games in marketing. The “Bad News” by Noreen was the first AR style semi-auto .300 win mag. However I think it’s significant that MPA chose to debut their rifle at range day. To the best of my knowledge neither of the other manufacturers have ever participated in a range day with their rifles. That may or may not mean anything but it seems significant to me.

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