Concealed Carry & Home Defense

Gun Test: Rock Island’s High-Cap 10mm

Guns and Gear Contributor
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By Mark Hampton, GUNS Magazine
Photos By Robbie Barrkman

If new offerings in 10mm Auto—both handguns and ammunition-are any indication—I would predict the cartridge is steadily regaining traction. Why the recent interest in 10mm? What niche or purpose could it fulfill? Since stumbling right out of the starting gate in a maelstrom, the 10mm almost experienced a quick and painless death. We are quite fortunate the 10mm didn’t vanish from history. Overshadowed by the .40 S&W, the 10mm is beginning to regain acceptance by the shooting fraternity and hunters alike who enjoy powerful, versatile semi-autos.

Last SHOT Show, I noticed several manufacturers offering semi-autos in 10mm. Rock Island Armory was one of those proactive firearm manufacturers seeing the resurgence in 10mm. This past year alone they offered several new offerings in their semi-automatic line-up. One particular model catching my eye more than once was their Big Rock—a 6-inch double stack.

To make a long story short, I had to have one. I tried to convince myself this gun could be used for personal protection (and it certainly can). I know for a fact the 10mm will suffice as a hunting round for such critters as wild boar, whitetail and varmints. That should be good reason enough. Besides, I just wanted one.


The Big Rock’s ejection port is large and scalloped so brass ejects without hindrance and remains reloadable.


An easy to see fiber-optic front sight is quick to pick up in almost any light. Note the Big Rock has no barrel bushing. Without a bushing, there is a 2-piece guide rod requiring a tool to disassemble.


An underframe accessory rail will handle anything you might wish to hang under the pistol, although the Big Rock weighs plenty with the long slide already.

Big Gun

At first glance, the Big Rock is, well, big. You could add “impressive” to the mix. It looks as if it could be a Special Forces carry piece for unique assignments. It’s definitely blessed with tactical appeal and eye pleasing with its Parkerized finish. When I saw the grips of the double-stack I immediately assumed they would be too large for my small hands. Wrong! Those G10 grips provide comfort and a secure hold. I could shoot the pistol with high-octane loads and never experience an issue with the grip being too large, something I’ve experienced on other high-capacity models. Better yet, the G10 grips were not abrasive in recoil and they look good.

Vertical serrations on the frontstrap compliment the mainspring housing full-checkered at 20 lines per inch. The slide incorporates rear GI-style serrations with a new, subtle Rock Island Armory logo located on the right side. No more billboard on the slide. The frame comes with a MIM beavertail grip safety, ambidextrous safety and MR3 trigger assembly. The trigger has vertical serrations. Like many others, I appreciated the fully supported, ramp-type match bull barrel, and wasn’t the least bit concerned when shooting full-house loads commonly used for hunting.

Those 16-round magazines inserted painlessly in the Medallion-type A2 magwell. That’s right, 16+1 of 10mm is a lot of insurance—and peace of mind! The LPA target-type rear sight, solid black as the ace of spades, complimented the dovetail-mounted orange fiber-optic front sight. When target shooting or hunting, especially running a variety of loads and different bullet weights for many applications, the adjustable rear sight is essential. A solid full-length dust cover with rail for accessories is standard. Serrations on the hammer provided consistent and sure traction for cocking. The overall fit and finish is good, especially considering this isn’t a $3K custom rig.


Ammo Availability

When my interest was first rekindled in 10mm, my concern turned immediately to ammunition. Would I be able to find any? After all, what’s a good gun worth if you can’t procure an ample supply of quality munitions? Well, after a little seek-and-find mission, my worries were laid to rest. As a matter of fact, I found far more options than previously imagined—and good stuff!

DoubleTap offers 16 different loadings (at least that’s what I counted last time). This company lead by Mike McNett, started their ammo business finding a niche market in 10mm and to this day, continue to provide an abundance of ammo from personal protection to heavy hunting stuff. Everything from 135-grain Nosler JHP to hardcast 230-grain WFNGC, DoubleTap has the 10mm covered.

Underwood is another ammo source who started up their business with 10mm. At last count, this company manufactured 12 different options for 10mm fans. They provide different bullet weights for an array of applications.

Hornady manufactures a great 10mm round using their 180-grain XTP bullet. From a variety of 10mm handguns, I have always found this ammo to be consistent and accurate—perfectly capable of taking a deer or hog with a well-placed round.

CorBon also provides several different options. I really like the 180-grain BCSP round in their Hunter line-up. This high velocity ammunition is a great choice for hunters. My previous tests results with any CorBon ammo have always revealed accuracy and consistency.

Recently I have been shooting HPR ammo with their 180-grain JHP. This factory offering has been accurate in both semi-autos and my Ruger revolver 10mm conversion.

Federal Premium has produced a 180-grain Trophy Bonded JSP giving hunters who always wanted to use a semi-auto as a serious big-game gun. This full-power cartridge provides enough horsepower to tackle any whitetail, wild boar or black bear. It’s common to find much of today’s 10mm ammo watered down producing ballistics almost identical to the .40 S&W. The new Vital-Shok load is vastly different. After testing this ammo in a variety of 10mm guns I was pleased with the accuracy and reliability. If you’re looking for factory load for hunting, this is a dandy option.

And speaking of heavy hunting loads, enter Buffalo Bore with their 220-grain hardcast round. I’ve been more than satisfied with this ammo from both the accuracy standpoint and effectiveness on Texas-sized hogs. Buffalo Bore provides the passionate cadre of 10mm followers like me with high quality ammo well suited for the field or range.

Winchester offers a 175-grain Silvertip HP, which is a good choice for self-defense. Their Super X line-up has been a steady performer in past evaluations of different 10mm handguns. This 175-grain Silvertip is very accurate from the Big Rock tested here.


The G10 grips proved perfect for holding on while touching off the heavier loads
without causing undue pain. The backstrap is nicely checkered, too.

RI_6 RI_11

After withdrawing the magazine and ensuring the chamber is unloaded a screwdriver starts the takedown sequence since the Big Rock has no barrel bushing. One of the biggest assets of the Big Rock is the fully adjustable rear sight, allowing you to zero the pistol for the wide range of bullet weights now available in 10mm ammo.

Their Super X line-up has been a steady performer in past evaluations of different 10mm handguns. This 175-grain Silvertip is very accurate from the Big Rock tested here.

SIG SAUER is the new kid on the block introducing a 180-grain full metal jacket great for practice and plinking. This new cartridge features a solid brass case with clean burning powder. The release of a 180-grain JHP for hunting wasn’t in time for this article, but the ballistics of the two are balanced so you have a less expensive FMJ for practice and JHP for business without re-zeroing. Well-known for their fine firearms, SIG continues to expand its popular Elite Performance line with the new 10mm.

American Eagle and Federal also offer a 180-grain FMJ I like to use for target shooting, whacking steel plates, and rock busting from a pond bank on our farm. This budget-friendly ammo has always been reliable and functions perfectly in a number of guns previously tested.

Depending on your mission, there are plenty of ammo choices when it comes to 10mm. I mention the availability and diversity simply to discourage anyone from having apprehension in this regard as I once did. With this cross-section of munitions in various bullet weights, I was anxious to see how the Big Rock would perform.

Along with 13 different boxes of factory 10mm ammo, I also had several different handloads with Hornady, Nosler, and Sierra bullets. Using a Redding T-7 turret system, quality Starline brass, and a canister of Bluedot, the 10mm Auto is painless to load. All of my handloads use 180-grain bullets.

With the help of my good shooting buddy, Joe, we set out to evaluate the Big Rock. I wanted Joe to help with all this shooting as he is much younger and has great eyes along with steady nerves. Joe would be able to squeeze the accuracy out of any gun plus he has a lot of experience with semi-autos. We started shooting from 25 yards. The first thing I noticed was how well the Big Rock handled recoil. When loaded, the gun tips the scales at more than 3.5 pounds, and this extra weight is beneficial in taming felt recoil. The G10 grips were an asset when shooting heavy recoiling rounds like those 220-grain hardcast bullets from Buffalo Bore. Compared to other 5-inch 1911 models in 10mm, the Big Rock is well mannered digesting full power 10mm ammo. The sights on this pistol are made for target shooting and we both could acquire targets quickly and precisely. Joe was getting groups ranging from 2 to 3 inches most of the time. Once in a while less than 2 inches materialized.

After 300 rounds or so we noticed accuracy deteriorating somewhat. So we gave the barrel a good cleaning and we were back in business with groups recovering nicely. After 500 rounds we had not experienced one malfunction. I thought this was pretty remarkable with both of us shooting all the factory ammo and my handloads. At the end of the day we both were pleased with overall performance of the Big Rock. What I enjoyed the most was not only the accuracy it delivered, but how well it handled the recoil of heavy 10mm ammo. This is a gun you can shoot for hours—literally.


Shooting the heavy, long-slide RIA 10mm was pleasant and enjoyable. Mark practices shooting from a field position at the range on his farm.

So, how will a big gun with high capacity fill a niche or void with shooters? The Big Rock will make a capacity, with a couple of extra magazines loaded will provide a lot of firepower. Personal defense concerns will be addressed by a fighting pistol launching multiple hunks of heavy lead. Hunters who appreciate heading to the field with a semi-auto will really like the Big Rock. It is pleasant to shoot, easy to control, and will make a serious hunting pistol for the field. I will be hunting with this gun come fall for whitetail and hogs—and there is plenty of quality hunting rounds available to make a viable, dependable hunting rig. Or one of my handloads (I haven’t decided yet.)

Currently I am looking for a good holster to carry this hefty 10mm. More than likely I’ll have Simply Rugged make a chest carry rig. I’ve used their fine leather in the past and have always been pleased. They even make a spare magazine pouch for semi-autos. For the size of pistol, their Chesty Puller system would work well for an across-the-chest carry.

Rock Island Armory continues to provide shooters with affordable, well-built pistols and I must say, the Big Rock will be added to my stable. My wife even enjoys shooting this 10mm. The Big Rock exceeded my expectations at a price-point neither depleting my savings or my wife’s patience. The Big Rock and 10mm go together like apple pie and ice cream.


The Big Rock performed well at 25 yards with Armscor ammunition. The factory round is a mild, inexpensive 180-grain FMJ, a perfect round for training and practice.


The 135-grain Nosler JHP from DoubleTap shot well during range sessions. The ability to adjust the sights proved a huge benefit.


Two-inch groups were not uncommon with a variety of ammo tested.

Pro Ultra Match HC
Maker: Armscor USA
Rock Island Armory, 150 N. Smart Way, Pahrump, NV 89060
(775) 537-1444,

Action type: Locked breech, semi-auto
Caliber: 10mm
Capacity: 16+1
Barrel length: 6 inches
Overall length: 9.5 inches
Weight: 3 pounds, 6 ounces
Finish: Parkerized
Sights: Orange fiber optic front, rear tactical adjustable
Grips: G10
Price: $1,344

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