Rock Island 10mm Upgrade Caspian Slide + C-More RTS2 optic


It’s no secret that adding a red dot optic to a handgun is a red-hot trend.

Over the last few years this has been catching on with polymer guns, such as the Glock MOS system, the Smith & Wesson M&P series and other manufacturers who are now configuring slides on a number models to accept optics.

Of course, adding optics to “old fashioned” handguns such as 1911s or wheel guns is nothing new. Bullseye shooters have been doing this for generations.

The difference is that putting an optic on a 1911 almost always entails outfitting them with a rail type mount. What’s new with this platform is that Caspian Arms, the venerable manufacturer of 1911 kits, now offers a optics-ready slide to accommodate a red dot.  Providing a mounting platform, along with the appropriately tapped holes, allows the end-user to easily place a red dot directly on the slide.

My starting point with this project was the Rock Island Armory Pro Match Ultra 6″. Out of the box this is an extremely accurate, well-finished gun. I simply tweaked it, so that it would easily accept a red dot, and turned it into something more applicable to my own needs.

Caspian Arms, one of the most respected manufacturers of 1911 parts and accessories, is a small company and they don’t spend much on marketing. They don’t have to. They have a great reputation for their products, mostly frames and slides which are used almost exclusively for competition guns. I suspect a good number of the winners at Camp Perry use Caspian frames or slides. I own a 1911 built with a Caspian frame and it’s one of my most prized possessions.

The Caspian/C-More combination on the RIA 10mm will work for everything from home defense to pig hunting

When I learned about the new Caspian optic-ready slide option I knew that’s how I wanted to modify my RIA PRO Match Ultra.  Essentially you tell the Caspian folks what optic you want mounted on your gun and they’ll machine a Caspian slide to match the footprint. This is not exactly a mass produced product but it’s faster and less expensive than having a gunsmith do a custom job.

I was introduced to this model at the 2016 SHOT Show in Vegas and was smitten. It was accurate, well finished and reasonably priced. RIA guns are manufactured in the Philippines which gives them a competitive edge in pricing. Just because the Phillipines is not traditionally thought of as gun manufacturing mecca don’t let that dissuade you from a purchase. RIA, aka Armscor, makes more 1911s than anyone else in the world and based on this model, I would not hesitate to recommend them.

Street price is about $950 which is a bargain, considering that you are getting a match grade 1911. The stock gun served as the perfect platform for this project.

You’re not going to be shooting Bullseye matches with a 10 mm handgun but it’s ideal for hunting and taking to the silhouette range. The 10 mm chambering, combined with the extra velocity afforded by the 6” barrel, makes it perfect to reach out and touch something at a long distance.

It’s a great little gun but with a red dot it becomes more functional by an order of magnitude. That was my rationale for adding this slide/optic combo.

For the optic, I opted for the C-More RTS2.

C-More Systems is a family owned optics company that you may not hear about as much as the larger manufacturers but don’t let that put you off. They specialize in high end gear for race guns and have been doing so for years.

Founded in Manassas, Virginia in 1993, its primary products are red dot sights for M1911 pistols, Glock pistols, and AR-15s. Their sights come recommended by FN Herstal for the M249 SAW (light machine gun) and M240 machine gun. The company also manufactures the M26 Modular Accessory Shotgun System for the United States Armed Forces.

I really liked the lock-down feature which ensures that your windage and elevation adjustments stay put.

Quality is first class because it has to stand up to the pounding it’s inevitably going to get in a competitive or combat scenario. Hence many of C-More’s clientele tends to be Bullseye competitors. That said, it’s reasonably priced—much less than the expensive stuff from Europe or this country for that matter.

The C-MORE RTS2 series reflex sight is C-More’s newest product and is among their smaller reflex sights. It offers the shooter a parallax free design which means you can acquire a target without having to center the dot in the lens. The company uses a “beam-splitter lens” manufactured of hard coated glass to protect the product from scratches.

The housing is manufactured from aviation alloy and the electronics are designed to deal with hot loads from large caliber firearms. In short this system is perfect for an energetic round like the 10 mm. It offers 1 moa click adjustment for both windage and elevation. A 10 position, manually operated push button switch offers plenty of options for intensity adjustment and it will shut off automatically after eight hours of inactivity. A nice touch is that after setting your adjustments you can lock them down securely with a separate tweak using an Allen wrench.

One of the coolest features about the RTS2 is that you can replace the battery (a CR2032 lithium model) without dismounting the sight. That means you don’t have to re-zero it every time you replace it—which shouldn’t be that often. Very clever those Americans. What’s more, the battery compartment has an O-ring seal to keep it waterproof.

It’s a cool little optic that works splendidly for longer shots, which was exactly what I wanted.

Mounting the optic couldn’t have been more straight forward. The Caspian machine shop tapped the holes so all I had to do was to cinch down the RTS2 and apply a little Loctite.

Adding the slide assembly to the frame is pretty standard stuff if you own a 1911. However, the RIA model has a 20 lb recoil spring to contend with. Shall we say it’s a bit challenging to put back on.

I did need the services of a gunsmith to fit the barrel to the slide. The slide fit on the rails of the frame perfectly so nothing had to be done in that department.

I preferred Magpul grips over the stock RIA offering, which I felt were overly aggressive.

Magpul Grips

In addition to the slide assembly I added one more essential item to transform this gun into a much more user-friendly firearm–a set of Magpul MOE grip panels. Why do so? There’s nothing inherently wrong with the stock (VZ) grips on the RIA but like all things in life it’s a matter of preference. I thought they were too aggressive for my sensibilities and started to literally grate on me. I understand that control is an issue with a 10 mm handgun. However I found the Mapguls, which have diamond-shaped cross section to prevent twisting in the hand, offered both control and great ergonomics. They felt better in my hands and at $19.95, didn’t break the bank.

Working up a load

I reload and this resolves a couple of issues right off the bat. First off, store-bought 10 mm ammunition is expensive. Not only can you cut your ammo bill in half by rolling your own, but just as importantly you can manufacture cartridges precisely to your own requirements and often with more potential accuracy than a factory round. The challenge is of course coming up with an alchemical equation that takes into account the weight of your bullet, the length of your barrel, the make of your primer and a half a dozen other factors.

What I found really useful in the 10 mm space was to join the 10mm Firearms forum. As you’d expect, these are hard core enthusiasts who have done a lot of experimentation when it comes to reloading. They were incredibly helpful.

Finally, none other than famed shooter Jerry Miceluk was also a source of info. He likes heavier bullets for longer distance shooting which meant at least 180 gr. I wasn’t about to second guess him.

So what did I discover? First off a disclaimer. This was hardly a scientific endeavor but I did shoot hundreds of experimental rounds for this article. One of the primary lessons that I learned (and this most likely is not going to be an epiphany to hand loaders) is that hollow point bullets are the most accurate. However, at 25 yards and under, I didn’t see that much of a difference between the flat point and the hollow points.

The Montana Gold 10 mm 180 gr HP bullet was accurate at 100 yards.

At 50 yards plus jacketed hollow points (such as Montana Gold) also worked splendidly. Between the jacketed and the plated I would say the former were more accurate than the plated bullets at longer distances. I used both 165 and 180 grain bullets, jacketed and plated. I also opted to experiment with some locally cast 180 gr bullets from a true craftsman here in Hawaii.

That said, the results were pretty nuanced. That means a really competitive shooter will appreciate the difference between the jacketed and plated bullets. The average shooter, just plinking away, is not going to see much of a difference, if any between plated, jacketed and cast bullets.

Picking your powder

My selection of powder was not entirely scientific.

I have a quantity of Accurate Arms (aka AA) powder from Western Powders on hand so I used it for my experimentation. I’ve used this brand for years with 357 and .41 magnum loads with stellar results. The very same powders that excel in the magnum space, AA #7 and AA #9, are excellent for the 10 mm which is essentially a magnum round. (For good measure, I also tried AA#5 which also worked well).

What I liked about AA #7 and AA#5 is that you don’t have to max out on the load to get good efficiency. AA #9 on the other hand usually (but not always as I found out) needs to be loaded on the heavier side. Thus you can get away with less than a full-on load with AA#5 and #7 and get some very impressive results.

Why does this matter?

My bias, perhaps from shooting Bullseye guns for years, is come up with a load that is the most accurate with the least recoil. A full house load has it’s place but too much recoil too much of the time is a drag. Not only is it going to put more stress on you, but on your firearm as well.

My go-to powder for the Caspian/RIA 10mm was AA No. 9 for 180 gn bullets.

With this in mind, I managed to come up with a couple of balanced loads for this gun which worked exceptionally well:

  • I found that 12.5 gr of Accurate #9 over a 180 gr (plated) bullet from a plated or jacketed bullet such as Montana Gold hollow point was particularly effective. This load also worked well for the Rainier 180 gr FP (a bullet with a flat point that resembles a truncated cone).
  • For a 165 gr jacketed or plated bullet (either hollow point or FP) 11-11.5 gr of Accurate #7 worked great. 8 gr of AA#5 also worked wonders for the 165 gr plated bullet.
  • If you’re shooting a cast 180 gr bullet, a light but very accurate load was 8 gr of AA #7.
  • The recipes for all of the AA powders on this round usually fills at least half of the volume of the cartridge. That’s a good thing because if you accidentally double-charge, the powder will spill thus tipping you off.

Picking the right load for a plated bullet

There is one important issue to consider when loading for the 10 mm or similar magnum style round. Donny Shride, former owner of Rainer Ballistics, suggests that you use the recipes for jacketed bullets of the same weight and style. Thus if the recipe calls for 165 gr hollow point, jacketed bullet, that same recipe can be used for a plated 165 grain hollow point.

However there is an important caveat.

Shride stresses that you should only load plated bullets to a “mid range” level. Thus, if the reloading guide says use 10 to 13 grains of powder for the particular load, you shouldn’t go higher than 11.5 grains.  The base of plated bullets (unlike jacketed) tend to deform more easily under high pressure loads so it’s not a good idea to push them too much.

Western Powders publishes a very useful reloading guide and there’s no shortage of “pet loads” on forums. Of course you have to be a bit careful about using data off the internet. Naturally the standard reloading guides from Speer, Lyman and others also have data.

A tack driver at 25 yards. Montana Gold 165 gr bullet.

Shooting the gun

The RIA/Caspian hybrid was wickedly accurate. At 25 yards it wasn’t much of a chore to get a decent group. At 50 yards, it’s going to take a bit more work, as you’d expect. Within a few minutes of getting the sight zeroed in, I got some pretty good groupings that I’m sure would be even better with a few more outings.

I was also able to accomplish a personal goal with this setup–to whack an 8″ diameter gong at just over 100 yards.

For those not familiar with the 10 mm, it’s not a handgun for the fainthearted. You’re going to get a good dose of recoil commensurate with magnum-like character of the round. Of course recoil can be tweaked with your loads. If you don’t like the heavier loads, 8 gr of AA#5 was a sweet load for a 165 gr plated bullet.

Other Tweaks

The only other modification I made was lightening up the trigger perhaps by half a pound. The stock trigger is excellent but I wanted it modified to my own specs. At the time of publication I’m also experimenting a bit with the recoil spring. The stock spring is 20 lbs. With the heavier Caspian slide to move I put in a lighter spring and so far that seems to help the gun to cycle. Of course, it still needs to be broken in so we’ll see how this plays out. Ordinarily I don’t think it’s a good idea to second guess the factory settings but in this case I did–at least for the time being.


Let’s begin with the optics. The C-More worked splendidly.

The use of a red dot, particularly for longer shots, was exactly what I wanted. The red dot is a crisp little orb and 6 MOA functioned perfectly for my needs. The C-More RTS2 retails for $418.49 on Amazon.

There are several advantages going with a custom slide/optic combination. First off there’s no rail to contend with. All you do is mount the optic on the slide by screwing it on. It sits lower and is aesthetically more pleasing and cleaner than a rail. There’s nothing between the optic and the slide.

To fit the barrel, material had to be removed from the slide in several areas including the edge of the dust cover.

The disadvantage is that you can’t change your brand of reflex sight unless it has the exact same footprint as the original optic. It’s also going to be a bit more expensive adding the whole assembly rather than a rail.

Price for the Caspian Long Slide (which I needed for the RIA gun) is $302 with an additional $61 to machine the rear sight cut. The serrated round top option for the slide is $38. Caspian will be able to machine a cut for any slide. However, in some cases Caspian may want you to send your optic to them to make certain they have the correct dimensions in order to do the work. Your best bet is peruse their catalog and determine what part you want.

One more caveat. Note as alluded to earlier, you may have to spend a few more bucks to get your Caspian slide fitted with the barrel. This necessitated some removal of metal from the slide in several areas with a dremel. It wasn’t major surgery but you want to leave this to the pros. In my case it was the deft hand of my gunsmith, “Bobot” Duquez, a superb Hawaii gunsmith.

The entire upgrade endeavor will set you back about $1000, including gunsmithing. However, considering the price of a decent accurized 1911 without optics will run at least $2000, this is a bargain.

If you’re a 1911 owner and you want to add a red dot, the Caspian “Optics-ready Option”, in combination with a quality sight such as the C-More RTS2, is an upgrade worthy of consideration.