Tricked-Out Trunk Gun

Springfield’s “Shorty Saint” Morphs Into A Doomsday Defender

Mike wanted a bit more EDC firepower, so he put together this “trunk gun”
based on a Springfield Armory Saint AR Pistol in 5.56.

The reconfigured SAINT is short, powerful and loaded with lots of back-up ammo.

I’ve a bit of a track record on carrying “too much” gun. While I started my CCW trek with the ubiquitous J-Frame .38 Smith, I soon jumped up to a Springfield Armory TRP .45 with two spare mags, then on to a Springfield XD45 full-size — again with two spare mags. Were these big guns easy to carry? Not really. Worth it? Yes.

I’d toyed with the idea of adding a “trunk gun” rifle to my setup to allow me to downsize my CCW gun a bit — you know the whole, “a handgun is just a means to fight to your rifle” deal? But the complications in my state on having a loaded rifle in the car were just too much of a hassle. Also, the bulk of an in-the-trunk setup was another hurdle. Then I saw the Springfield Armory Saint AR Pistol in 5.56mm. Was this the answer to my dilemma?

The collapsible SBPDW stabilizing brace helped Mike shave off about 3" of overall length from the Saint.
Mike used BLACKHAWK!’s push-button sling swivel and single-point Storm sling as well.

The Basic Item

For those unfamiliar, the Saint AR Pistol is a handgun version of the 5.56mm Saint rifle. It sports a stubby little 7.5″ barrel topped off with a “blast diverter” on the threaded muzzle — a nice feature on a gun to prevent it from becoming a flamethrower in any other situation.

The Melonite-coated stainless steel barrel has a 1:7 twist and a low-profile pinned gas block under the free-floated M-LOK handguard, which features a “hand stop” to ensure you keep your digits clear of the shorty barrel’s barky end.

At the back end of the pistol is an SB Tactical SBX-K stabilizing brace on the receiver extension. Everything between is familiar AR territory — forged upper and lowers with Springfield’s Accu-Tite “tension system,” a Bravo Company triggerguard and Mod 3 pistol grip and a Magpul 30-round PMAG. If you can run an AR carbine, you can run the Saint Pistol. It also comes in a nice zippered bag with dual mag pouches.

While “shorty” ARs have some downsides — such as potential functioning problems and reduced ballistic performance from the short barrel — the Saint has many advantages to offset these concerns. It’s small and would take up little space in the trunk. Plus, I know ARs and would be intimately familiar with the pistol’s operation. It’s also officially a handgun, which makes it simpler for me to legally carry it in my car with my CCW permit. And it would give me a lot of backup firepower to my primary CCW pistol. But, as ideal as the Saint was out of the box, I wanted to tweak the setup a bit.

While the SB Tactical SBX-K is perfectly functional, I desired something a little more compact, leading me to the company’s SBPDW. This three-position adjustable brace comes with its own proprietary tube and gives you a really nice stabilizer that shortened my Saint’s overall length from 26.5″ to 23.5″ when fully collapsed. It has a QD attachment point at the 6 o’clock position, and just plain looks cool.

Since the pistol comes without sights, I settled on a Vortex SPARC AR red dot. Compact and light, the SPARC added minimal bulk but still gave me a solid 1X field with a 2 MOA and easy-to-use controls. It runs off a single AAA battery. The acronym, incidentally, stands for Speed Point Aiming for Rapid Combat. It’s an accurate description.

The Vortex SPARC AR red dot sight proved ideal for the project.

The stubby 7.5" barrel is topped off with a “blast diverter” — an absolute necessity.

Accessible On-Board Ammo

I found with the optic mounted the Saint would not fit in the case with the 30-rounder PMAG installed. I picked up a Magpul Gen M3 20-rounder that would (along with two more 30-rounder PMAGs). I also wanted a way to sling the gun, so I equipped the SBPDW stabilizer with a push-button sling swivel and a single-point Storm sling, both from BLACKHAWK! I could simply pull the gun from the bag and sling it in a matter of seconds.

As it stood, I’d have a loaded 20-rounder in the gun and two fully loaded 30-rounders in the case’s mag pockets. As I wanted as much on-board ammo with the gun as possible, I also picked up BLACKHAWK’s M4 Collapsible Stock Mag Pouch. I decided to attach the pouch to the handguard and put a 30-rounder in there.

I positioned the pouch so the magazine would be on the left side of the handguard, with the mouth of the pouch facing rearward and the rounds in the mag pointing downward. To reload, the magazine would be pulled back and out then rotated 90 degrees to be in alignment with the magazine well. In this position, the spare mag clears the gun easily and does not block the bolt catch. The forward retaining strap of the pouch did prevent me from putting a backup iron sight in the forward position, but I decided this was worth it for the extra ammo.

I also wanted to add an extra layer of security. When I am carrying a CCW handgun, it’s never out of my control. With the Saint plan, I’d be tossing it in the back of my SUV or in the trunk of the car. To keep meddling hands away, I purchased a simple luggage lock with a programmable three-digit code to slip through the slots of the case’s two zippers. The charm of this system was it would keep the gun secure and wouldn’t require me to carry around a key (but if you opt for a code, be sure it’ll be one you’ll remember).

The result of my tinkering gave me a secure trunk gun providing 50+1 rounds on the gun, with a spare 60 rounds in the two mags in the case. I could sling the pistol easily, and its Vortex optic would make it more than effective out to 50 — even 100 — yards. That is a lot of defensive firepower in a very small package.

So the SAINT would have as much on-board ammo as possible,
Mike put a Blackhawk! mag pouch on the handguard of the pistol.

The original Springfield case proved to be a good carrying system for Mike’s “trunk gun.”
Note the dual mag pouches.

It shoots! Federal Premium Gold Medal 73-gr. Berger loads punched sub-inch groups at 50 yards.

Rounds Downrange

Of course, the “genius” of my reconfiguration project wouldn’t matter if the gun didn’t work. So I set it up in the case as I would carry it in my trunk and took it to the range with a selection of Black Hills, Federal and Winchester ammo, in bullet weights ranging from 50 to 73 grains. Curious about velocity loss in the stubby barrel, I also brought along my chronograph.

I shot for accuracy at 50 yards from the bench and consistently got groups in the 1–1.5″ range. Federal Premium’s Gold Medal 73-gr. Berger boattail gave me the tightest group at just under 0.75″. The gun ran all the loads without a hitch — no mean feat with a short barrel and a DGI system. Velocities ran in the 1,900 to 2,400 fps range — well short of what you’d get with a carbine but still respectable. Noise and concussion — while notable — were less than I expected.

Ergonomically, my entire setup worked out well. I was most concerned about the mag pouch on the handguard, but it did not obstruct any controls and held on just fine. Also, the slimness of the handguard made wrapping my hand around it and the pouch no problem. Looks like maybe I am a genius after all!

Although not cheap, the overall cost of my “trunk gun” was still manageable. The Saint pistol has an MSRP of $989, the Vortex SPARC AR red dot $259, the SBPDW brace $299, the BLACKHAWK! gear a total of about $80 and the Magpul mags came in just under $45, total.

If my being over-prepared theory means I’ll avoid danger is true, this rig should ensure I die peacefully of natural causes a very old man. And who knows, now maybe I can carry a pocket-sized .380 as my primary!

Springfield Armory, Ph: (800) 680-6866

BLACKHAWK!, Ph: (406) 284-3840

Vortex, Ph: (800) (426)-0048

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