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STI Duty One CO2 BB Pistol Kit #101


STI Duty One Real steel background

The STI 2011 frame was lighter than most modern 1911 frames. However, it wasn’t as strong or reliable as a conventional steel 1911 frame.

Early in the 1990s, Texas gunsmith Virgil Tripp built custom 1911 pistols for the growing IPSC market.

His attention to detail and the quality of his products quickly brought commercial success and in 1993 a young engineer and CAD specialist called Sandy Strayer joined Tripp Research Inc.


In the late 1990s, Tripp and Stayer revolutionised the 1911 market by introducing the first range to feature their 1911 design, the Stayer/Tripp series.

This weapon has a modular frame using fiber-reinforced plastic for the trigger guard, grip, and magazine well. The upper part of the frame is made of metal, allowing the use of the standard AEG’s bolt carrier group.


The STI International Duty One

The Duty One is one of the most popular STI pistols in the market.

However, unlike many semi-auto pistols, this isn’t primarily intended as a target shooter.

This is a great pistol for home defense. The Smith & Wesson M&P45 is a well-designed


The Duty One features a patented STI International lightweight trigger, a commander style hammer and is supplied with a distinctive matte

An ambidextrous thumb safety is provided along with the grip safety.

This bike is available in standard and “lite” form, which uses an aluminum frame.

This duty knife, introduced in 2014, features a new handle shape and serrations designed to enhance handling.

The ASG STI Duty One

The ASG STI Duty One is a short-stroke, CO2-powered replica of a military STI with a single-stick, or drop-out, magazine and a short under-barrel accessory rail.

CO2 is retained inside the grip and accessed by removing the backstrap and grip base.

This replica is made in Taiwan on behalf of ASG, and is available in 4.5mm and 6mm sizes.


The duty one with blowback is the best choice for many shooters who prefer the recoil of a more traditional.22 caliber rifle and those who would like to shoot the rifle in their home without disturbing the neighbors.

This article presents the figures below and information I got from using the blowback version.

A non-blowback version of the RRS 2.0 is a little bit longer in length and has more sections, but I haven’t tested it out yet.

I think the 5.0mm version is available in matte black finish only though there is a two-tone version of the non-blowback and the 6mm blowback versions with a polished slide. 

Two-tone 6mm version

During a blowback shot, the slide will move through less than the full range of travel. When the last round is fired, the slide locks back.


The thumb safety, magazine and slide release work as they did on the original pistol but the grip safety is moulded in place and has no function.

The ASG STI Duty One is NOT a semi-auto pistol. This is a true revolvers design and cannot be field stripped.

Functional Accuracy

This is the version I use for my personal use. It is a replica version with a blow-back. The trigger is designed to be single action only, so you don’t need to worry about it firing unintentionally.

The slide catch, magazine release and thumb safety work as they did in the original weapon. The slide moves through restricted travel, compared to the cartridge version.

The grip safety is moulded in place but has no function. In the cartridge version the slide release catch is located on the right side of the gun. On this version the slide cannot be extracted, and removing the slide is impossible.

The CO2 chamber is accessed by pressing a button in the base of the grip, which allows the grip panel that forms the base of the gun to be removed. CO2 can then be inserted and tightened and pierced using the plastic tab at the base of the grip.

The tightening tab is a little small and fiddly for larger fingers but with a bit of practice this can be done without too much drama. It’s a bit difficult to remove the used CO2 cartridge.


The old CO2 cartridges have been around for years now and many of us will have a box of them in our garage somewhere. It was rather easy to fit the cover panel; however, the fitting of the loading tab is a little tricky.

Loading the pistol type magazine reveals the first of this replicas’ idiosyncrasies. The follower locks up, which makes it easier to load bullets into the mag tube at the top of the magazine.

However, if you then remove the follower, the BBs will shoot back out of the top of the magazine. To prevent this, you must press the magazine’s top against the finger of your left hand.

When you have CO2 and BBs loaded, the ASG STI Duty One feels great. The deep, rounded rubber grips and angular frame will help give you a firm and consistent grip.

The STI International obviously knows a lot about how to make a handgun that handles well. Their ASG version does this nicely. This feeling is reinforced when you pull the trigger – a loud bang, a strong blowback and a quick follow-up shot put your marksmanship to the test.


The most important thing to know about this pistol is that the second it fires, the second you pull the trigger, it will also reveal an odd feature about it. Like many blowback replicas, the blowback action doesn’t always have a cocked hammer, so that you don’t get immediate shooting after the trigger pull.

This occurs when the rifle is fired. The long first part of the trigger pull and the movement of the bullet are clearly felt. If the rifle is lying flat, and if you pull the trigger only a little faster than your normal firing rate, then the BB may just fall out of the front of the barrel instead of rolling over it.

It’s better to pull the trigger firmly and fairly quickly (so that the trigger pulls the bullet into alignment with the barrel), and then aim with care. But this doesn’t help with accuracy.

This issue seems to vary, but on my Duty Ones, it was less of a problem than on the other two models. If, for any reason, you pull the trigger halfway back and don’t fire it, when you next pull the trigger you will load another BB into the breech and you’ll then

If you’re an avid gun shooter, you know the importance of pulling the trigger quickly and confidently every time. Loading the BB on the left side of the chamber will lead to a double-loading, which is a common error for first-time shooters.


The loud bangs and the blowback make the duty one feel powerful, but the numbers don’t really back this up. The first example that I ever received from ASG, it was a 4.5mm STI and it chronographed for around 400 fps.

In fact, they’re not really very respectable at all. However, the numbers are certainly well short of the 441fps claimed by ASG. Accuracy was average without being great. Although they lack white dots, the sights are clear and easy to read but grouping with two of my Duty Ones was around 1¼”- 1¾” at six yards – fair but not great.

A notable difference in the third example was that, whereas the first example was almost a perfect pass, the second was markedly worse than the first.

CO2 usage is fair for a blowback replica gun with three magazines (60 shots) of full-power shots available from a single CO2. After you’ve shot a certain number of shots, you’ll eventually run out of puff, and the CO2 will be depleted in the magazine somewhere around the 70th shot.


The ASG STI Duty One appears to be reliable and reliable. The slide locks back every time and I had no mechanical problems or failures with any of the examples I owned. The slide release and magazine release are only on the left side, so this isn’t the perfect pistol for someone who’s left-handed.

Quality And Reliability

The ASG STI Duty One is a well built bike that rides very smoothly. It’s nice to be able to ride it for hours without feeling any of the usual tiredness from pedaling. All the features and details are in place without any rattles or movement, and the seams are well concealed.

The rubberised grips are a particularly nice touch and the matte black finish seems more durable than the finish on many replicas. I haven’t heard of anyone experiencing this problem, either, though I’ve heard of owners who say that theirs have been affected by it. If you experience this, just bring the gun to GunBroker.

The operational issues noted in the Shooting section are probably due to design flaws rather than manufacturing defects. This seems to be a good quality replica that is available at a really reasonable price.

STI Duty One CO2 BB Pistol Kit Specs

Max Velocity383 fps
Overall Length8.66″
Weight1.82 lbs
Suggested forPlinking/Fun
Caliber.177 (4.5mm)
Barrel Length4.55″
Shot Capacity20
BarrelSmooth bore
Front SightBlade
Rear SightFixed
Body TypePistol
Fixed/adj. powerFixed

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