Sig Sauer MCX Part 3

Sig Sauer MCX Part 3

Tactical Air Rifles and Optics

Build a Custom Airgun

By Dennis Adler

Optics options for the Sig Sauer MCX air rifle, as well as other tactical designs like the Umarex Beretta CX4 Storm, include very affordable red dot scopes like the BSA RD42 mounted on the Beretta, and UTG CQB red/green scope on the MCX.

Sig Sauer MCX Part 2

Sig Sauer MCX Part 1

As I have noted in Parts 1 and 2 the most important features of the Sig Sauer MCX are its authenticity of design and ability to work in combination with all types of optics from the very expensive Sig Sauer Bravo4 battle sight used on the actual 5.56mm military rifles to affordable air rifle optics like the UTG CQB red/green dot. This is a large 4.25 inch overall length optic with a quick mount release and locking windage and elevation adjustments screws on each click adjustable turret. The second airgun sight tested with the Sig Sauer is a personal favorite, the BSA RD42 which is suitable for pellet rifles and CO2 pistols as well as .22 caliber firearms. This is a durable and proven design that has been around in one form or another for many years. I have an RD42 that is about 10 years old and still works as good as the day it was purchased. It has been on everything from CO2 target revolvers to .22 caliber rifles and worked without fail.

For the purposes of showing the ease of mounting, I have also attached these same sights to the fine Beretta CX4 tactical air rifle (first reviewed in Airgun Experience articles No. 34, No. 35 and No. 36) and equipped for that review with an Aimpoint Micro H-1, another high end (over $600) optic used on .223 and larger caliber rifles and pistols.

The 10 Meter Test

The MCX has an overall length of 34.7 inches with its faux suppressor shrouded 17.7 inch internal barrel. Weight is a substantial 6 pounds, 12.5 ounces empty. A 5.56 caliber MCX has a 16-inch barrel and weighs 5.6 pounds.

The Sig Sauer’s 30-shot belt fed rotary magazine is easy to handle and loads easily into the magazine well.

For the test I used RWS Meisterkugeln Professional Line 8.2 grain lead wadcutter rifle pellets. Most airgun tests with blowback action pellet guns and rifles are done at 10 meters (33 feet) which is the competition distance for air rifles, and this is where I decided to do the initial test of the Sig Sauer MCX. The gun is easily capable of 50 foot accuracy and more, but due to high winds outdoors, I was confined to the indoor range. Trigger pull on the test gun averaged 6 pounds, 10 ounces. Take up is 0.5 inches with moderate stacking.

A light slap with the palm of the hand and the magazine is seated.

After 8 rounds to make sight adjustments with the Bravo4 optical battle sight, I reloaded and hefted the 9 pound, 3 ounce rifle (as equipped and fully loaded), and began continuous firing at 1 second intervals from a standing position. All 30 shots grouped inside the center ring and red bullseye of a Birchwood Casey Shoot-N-C silhouette. Maximum spread was 1.99 inches with 10-shot clusters and multiple overlapping hits averaging 0.75 to 0.875 inches. The belt fed Sig pellet magazines functioned perfectly and with extra pellet belts loaded, switching out and reloading magazines was very quick.

The first 10 meter test (actually shot indoors due to high winds), was with the MCX and the Sig Sauer Bravo4 battle sight made for the cartridge-firing models.
Does a $1,299 weapons sight designed for use by the military and law enforcement make this airgun any more accurate? Just a bit, with 30 consecutive shots on target measuring 1.99 inches.

I swapped out the Bravo4 for the BSA RD42, sighted it in and repeated the test from 10 meters. Again firing at 1 second intervals I had a total spread for 30 rounds of 2.65 inches, but the spread would have been 2.50 inches were it not for a flyer in the 10 ring. Even deducting that one the group would have been a full 0.51 inches wider than with the Bravo4. However, within the 30 shot group, two-thirds were just a hair under 2.0 inches with a best 10-shot cluster at 0.65 inches, all in one ragged hole that totally blew out the paper target.

How did the Sig Sauer MCX equipped with the BSA red dot do against the Bravo4? The BSA and Sig combo put 30 shots in the center ring and red bullseye at 2.65 inches with the majority of 10-shot groups measuring under 2.0 inches.

Next up I went green with the UTG CQB optical sight. The UTG is a gem when it comes to mounting on the top rail, just as fast (though not quite as solidly) as the Sig Sauer Bravo4. Of course, the UTG Tactical Dot Sight comes in at $1,250 less, so you need to be a little flexible! What it offers for just fifty bucks is a quick detach mount, flip- up lens caps, a choice of red or green dot reticles but a smaller 38mm tube diameter. At 10 meters, it remains a darn good air rifle sight for the money. But does it make the Sig Sauer MCX any more accurate?

The UTG CQB red/green dot scope looks right at home on the Sig Sauer MCX CO2 model.
The UTG’s bright green center dot helped the MCX deliver 30 rounds inside of 3.0 inches, with 10-round groups averaging under an inch with multiple overlapping hits.

With the UTG set on the green dot, total spread for 30 shots was just under 3.0 inches, the widest spread, but 10-round groups came in at an impressive average of 1.0 inches, again with multiple overlapping hits. Bottom line, a $50 optical sight on an air rifle at 10 meters can just about hold its own against a high end optic made for a 5.56mm semi-auto. The underlying accuracy of the Sig Sauer MCX with any kind of optics at 10 meters is that it can consistently put rounds on target at under an inch. For the final proof I did the test one more time with the flip-up BUIS and ended up with a best 10-round group measuring 2.25 inches. Not bad, but not as good as with optics. Overall, it is hard to fault the Sig Sauer MCX CO2 model for anything but its non-functioning features, but certainly not for those that do.

A word about safety

Tactical air rifles provide the look, feel and operation of their cartridge-firing counterparts and this is one reason why they have become so popular. Air rifles in general all look like cartridge-firing rifles, models like the Sig Sauer MCX even more so, and it is important to remember that the vast majority of people can’t tell an air rifle from a cartridge model. Never brandish an air rifle in public. Always, and I can never stress this enough, always treat them as you would a cartridge gun. The same manual of operation and safety should always apply.

15 thoughts on “Sig Sauer MCX Part 3”

  1. Despite a few flaws the SIG is the way to go for AR practice. I would like to see a 12 gm co2 adapter, more fps and fully functional controls. Take home message is that for 10 meters ,airgun optics are more than adequate. If the fps were increased to say 800 plus fps with 8 gr pellets ,this could be an alternative to 22 lr for practice at ranges out to 25 yards

    • When weather permits I am going to give the MCX one last test using the Bravo4 optics at 25 yards with the lighter weight Sig Sauer alloy pellets. The Sig cast alloy rounds should increase velocity and hopefully range and accuracy with the 88 gr. CO2. Stay tuned.

  2. wonder if the Umarex 850 12 gm co2 adapter would work with this rifle? They make another for sale in Europe specifically for the 1894 lever rifle that is a little shorter, have not seen it for sale here, why I don’t know.Would make this a more versatile rifle

    • It may still be possible to get the Lever Action Rifle 2 x 12 g CO2 adapter here in the U.S. A couple of years ago, the publisher of Airgun Hobbyist told me that Umarex U.S.A. was going to have a few of the Lever Action 2 x 12 g adapters available in the shop at their Arkansas headquarters. I was advised to call Umarex in Arkansas and ask to purchase one. That’s how I got mine.

      The Daisy Winchester MP4 tactical pellet rifle replica uses 2 x 12 g CO2. If you don’t want the 88 / 90 g CO2 pellet rifles, you might consider the MP4 as an alternative.

      • The reviews of the Winchester MP4 have been less than stellar. I am second to none in my hatred of the 8 round rotary mags that need to be flipped. In the 1894 they’ re a different story. Will wait and see what happens in lever guns . There are rumors of some new ones appearing. If I had to have an AR type 177 , would go for the Sig, just don’t like the big 88/90 gm co2. Not cheap anymore and supposedly shouldn’t be left in if not completely emptyied. Can get 40 12gm co2 locally for $17.Thanks anyhow

        • You’re right about the MP4 reviews not being stellar, but keep in mind that it was not designed to be any better than it is. If they had designed it as you have suggested, it would cost several hundred dollars and few airgunners would buy it. However, in my experience, the MP4 does reasonably well with some pellets. I don’t regret buying the MP4 because I didn’t have high expectations for it.

          If you do choose to buy and MCX or MPX, it would be worth your while to call Umarex at their Arkansas headquarters, ask for Tech Support I think, and just ask if they have the 2 x 12 g adapter for the Lever Action rifle. The worst that could happen is that they tell you they don’t have it. Or they might say they have one for sale and quote you a price. You don’t know until you call them. Until Umarex chooses to market those adapters in the U.S., it’s the best you can do to get one of those adapters.

  3. was looking at videos online of European IWA Show. It is amazing at the number of airguns not sold in the US. AK variants,all steel, FN Bullpup, Umarex 1894 John Wayne , Walnut Stock GAMO SWARM, Elite, and the final insult, what appears to be a Colt SAA Storekeeper , weathered finish 31/2 inch barrel. We are a second class market

  4. Please excuse me for coming back to this Sig Sauer MCX blog report after so many months, but I just received my new MCX and I have a question your blog report didn’t address.

    The foregrip appears to be adjustable with respect to its position on the rail by removing the two screws holding it in place. However, there appears to be two nuts inside the rail that may or may not be movable. Can the position of the foregrip be adjusted and how is it done?

    • I took a look at the MCX and it uses a Key-Mod style design on the handguard, but I see your point about the screws and the nuts inside the grip where they attach. That is not how a Key-Mod system works, so I think moving the foregrip might be a problem. There is nothing in the instruction book about moving it. I think it is in the best position as it forces the support arm closer into the body. I know different operators like their foregrip in different positions on the handguard but for this CO2 model I don’t see any advantage to moving it. I will ask the reps in the tech dept at Sig next week and get you an answer.

      • I’ve been thinking about this since I posted my question. Maybe the screws need only to be loosened. If the nuts are sized right, they are larger than the Key-Mod groove but smaller than the Key-Mod hole. With the screws loosened, maybe the grip slides back to let the nuts pull through the holes. Then at the new position, maybe the nuts are re-inserted into the new holes, slid forward to lock in the grooves, and then the screws are tightened. I haven’t actually tried this yet. I’m shooting the Sig Sauer P226 X-Five Silver today. So far I’ve spent most of my trial 10 shot groups chasing the sight adjustment from a bench rest position, but I think I might have the sight dialed in now.

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