Sig .45 ACP vs. Sig 4.5mm Part 1

Sig .45 ACP vs. Sig 4.5mm Part 1

“We The People” and “The Right of the People” 

By Dennis Adler

Mirror images? Not quite, but the two Sig Sauer models, the WE THE PEOPLE chambered in .45 ACP (left) and the 4.5mm (.177 caliber) CO2 model are as close as any two centerfire and blowback action air pistols can be in nearly every detail and feature, making the CO2 model the best 1911 training gun yet.

It is rare that a gun manufacturer becomes directly involved with both the design and the marketing of an air pistol that accurately duplicates the operation and handling of one of its own centerfire models. You can count them on one hand, Smith & Wesson with the M&P40, Webley & Scott, Sig Sauer, and very soon, Springfield Armory. Webley made certain that the CO2 version of its famous MK VI revolver of 1915 was built to the same standards as its legendary .455 caliber revolver by using the original blueprints; much the same will be forthcoming in the manufacturing of Springfield Armory semi-auto pistols and rifles as CO2 models. But Sig Sauer has gone so far as to deliver its WE THE PEOPLE Model 1911 in .45 ACP and 4.5mm (.177 caliber) as a matching pair, making this absolutely the most authentic blowback action CO2 pistol you can own.

Packaging is one of the big differences. While the Sig CO2 model doesn’t come in a blister pack, but rather a thermo molded two piece plastic shell that holds and protects the gun, the box and the ease with which the gun can be taken out (or stored) is much more work than sliding the locks on the .45 ACP model’s hard plastic form fit carry case. Of course there is that $1,361 price difference…and you can buy a Plano Protector Pistol Case for $10.

It is rare that I will do a one-on-one shooting comparison of a centerfire pistol with its CO2 counterpart for Airgun Experience, in fact, I have only done it once before with the Walther PPS and that was a stretch because the CO2 model is not a 100 percent match to the centerfire pistol. I have often made visual and technical comparisons with actual centerfire and CO2 models when applicable, but not shooting tests since many readers are not apt to spend $1,481 on a special edition .45 ACP Sig Sauer pistol to make their own one-on-one comparison with Sig’s CO2 counterpart. I have decided to make it easy for those of you considering it, by writing this special three-part article.

The details are so well executed that at a glace, even a long one, from the left side of the airgun only the caliber markings on the frame reveal that this is not a .45 ACP Sig Sauer.

Find a Hawke Scope

The recap on Sig Sauer’s achievement

There have been blowback action 1911 models with self-contained CO2 BB magazines since Umarex and Colt teamed up to make the Commander model in 2014. This is still one of the very best blowback action 1911s on the market despite the unintended affront to gun owners by adding arrows to show which way the thumb safety goes to put the gun on SAFE or FIRE. Umarex also gave the Commander a typical black airgun finish, (though we could call it a black Cerakote finish and live with it) and other CO2 models have come on the scene in the last couple of years that surpass the Umarex Colt for finish, like the Swiss Arms models, (though Swiss Arms doesn’t actually make a centerfire .45 ACP Model 1911). Getting the gun and gunmaker to be one and the same either through licensing or direct involvement is rare and even more so when both the centerfire and CO2 model are special editions with custom features and custom finishes. In that respect the Sig Sauer 1911 WE THE PEOPLE stands alone in any caliber.

The CO2 model, (top) shares the same features as the .45 ACP including a lowered and flared ejection port (even though there are no spent shell cases to eject), matching finish on the barrel, low profile sights, and alloy star pattern grip panels.

The Sig Sauer models are a breakthrough design that exemplifies forward thinking within the airgun industry. The CO2 Sig Sauer WE THE PEOPLE 1911 is so close, that unless you take note of the caliber stamped on the left side of the frame, or see the recessed 4.5mm barrel inside the rifled .45 ACP muzzle, the two guns are almost indistinguishable from the left side profile. From the right side the same is true physically, but aesthetically, the difference is revealed by the air pistol Warning on the frame, but even Sig Sauer has to play by some established rules.

More fine detail in the CO2 WE THE PEOPLE (bottom), are the 13 stars on the top of the slide. Even though the air pistol has the requisite Warning information on the right side of the frame, Sig Sauer places it in the same place as the manufacturer’s information on the .45 ACP model. (Also note that there is a retaining pin in the top of the .45 ACP model’s slide not used on the CO2 model.)

Even so, the attention to detail is evident in the CO2 model’s construction, and there remains only one other minor visual tell to the air pistol, the absence of an extractor at the back of the slide. That is the circle to the right of the hammer on the back of the slide. This is actually the back of the extractor itself which interlocks with the firing pin stop. This does surprise me, as Sig could have made this a finely molded in piece like the authentic-looking external extractor arm (rare on 1911s except custom models). The slide does have the correct lowered and flared ejection port, so this is really a very minor visual, but also a dead giveaway that this is not a cartridge-firing 1911.

From the back you can see the big mechanical tell on the CO2 model (right) which does not have an extractor, evidenced by the circle to the right of the firing pin on the back of the .45 ACP model’s slide. This is actually the back of the extractor itself, which interlocks with the firing pin stop. And, of course, the firing pin design for the CO2 model, to activate the magazine’s air valve, looks nothing like a 1911 firing pin. But the overall design and operating features, such as the matching palmswell grip safety are mighty impressive.

Beyond that, the WE THE PEOPLE airgun is true to the centerfire model in all its operating features, including ambidextrous thumb safeties. The models (.45 ACP and 4.5mm) also have the early flat checkered mainspring housing preferred on competition and tactical models, and matching skeletonized hammers and competition-style triggers. Both share low profile white dot sights (the .45 ACP model with tritium night sights), and the Sig model’s uniquely distressed finish.

The .45 ACP model of Sig Sauer’s WE THE PEOPLE is unusual in that Sig uses an exposed extractor. Take close note of the hammer design and contour, right hand ambidextrous thumb safety, and the Torx head screws for the grips. They are copied in full detail on the CO2 model below.
Skeletonized hammer, external extractor (though non functional), ambidextrous thumb safety and Torx head screws on the CO2 model match the centerfire pistol’s.

Distressed finishes are a personal preference. A gun collector might veer away from an original 1911 with this much finish wear, equal to about 50 to 60 percent condition in the Blue Book of Gun Values Photo Percentage Grading Scale, but without any pitting, so we are talking finish wear alone. This same appearance is used on both the centerfire and CO2 models. Aged finishes are actually common on reproduction Civil War era and mid to late 20th century pistols and rifles, and people pay extra for it, so Sig has actually picked up on a very popular trend among gun enthusiasts who want the look of an older gun but none of the mechanical wear.

The self-contained CO2 BB magazine for the Sig will fit in 1911 magazine pouches, another advantage for training exercises using the same gear as the centerfire pistol.

The Sig models (.45 ACP and 4.5mm) have SIG SAUER 1911 and 1776 engraved on the left side, and WE THE PEOPLE on the right. The airgun has the same depth and detail as the .45 ACP model’s slide. The trigger design is also identical, (though not adjustable) and the slide stop, ambidextrous thumb safeties, hammer and palmswell grip safety are matching in appearance and operation. The front and rear sights are actually mounted into dovetailed channels in the air pistol’s slide and the frontstrap and flat mainspring housing have the same fine checkering for a secure hold. The guns also share the same grip panel design with 25 stars on each aluminum panel, and thirteen stars in a circle on the top of the slide representing the original Thirteen Colonies. The CO2 model is as close to the .45 ACP Sig Sauer 1911 as it can get without firing .45 ACP rounds.

Thursday and Saturday we’ll run the two guns through a variety of holsters for carry practice and then head to the shooting range to see how the CO2 model does as a training gun for handling and accuracy against its .45 ACP counterpart.

1 thought on “Sig .45 ACP vs. Sig 4.5mm Part 1”

  1. Sig is taking understudy airguns seriously. I am a big proponent of an understudy 22 rimfire firearm , and a co2 understudy makes even more sense. Lower cost , cheaper to shoot, and flexibility of locations to practice, like backyard or basement. I understand they have a365 co2 pistol coming , which is a stroke of genius. Will be interesting to see what Springfield Armory airguns will offer. The M1 Carbine is long overdue. One of my favorite firearms. Other companies should take a long hard look at what could and should be offered.

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