Sig Sauer’s new M17 Part 3

Sig Sauer’s new M17 Part 3 Part 2 Part 1 Part 4

The P320 in military dress

By Dennis Adler

You can bet that Sig Sauer’s designers are proud of this air pistol. There may have been some less than enthusiastic reactions to the P320 pellet model, but there is no way to look at or handle the M17 that leaves you wanting for more, unless you just have to have a slide that locks back on an empty magazine and an adjustable rear sight. The M17 checks all the other boxes and get a bonus for absolutely authentic looks.

Blowback action air pistol designs and operation vary from as close to an actual blowback action centerfire pistol as possible, like the Umarex Walther PPK/S, to thoroughly accurate J.M. Browning short-recoil, locked-breech designs, like the Umarex HK USP, and internally contained, frame-mounted firing mechanisms (usually with stick magazines or reversible 8+8 pellet magazines) like the Sig Sauer Max Michel and Spartan 1911 models, or Umarex Beretta PX4 pellet pistol. The latter designs, if they have an open slide and barrel lug interface, only expose the top of the internal firing mechanism, rather than the top of the magazine when the slide goes back or is locked open. This configuration, used in the Sig Sauer Max Michel and Spartan 1911 models, formed the basis for the P320 M17 ASP’s internal design, but the definition of “basis” here is simply that, it was a starting point not the end result.

As for the handling part, that is unique in this field of air pistols for loading CO2 and pellets. The M17 magazine is a two-piece design that locks together forming a single self-contained CO2 pellet magazine for quick reloads and authentic handling.

The M17’s construction allows a lot of looking into openings to see how things fit together and function in unison. You can’t look inside any of the aforementioned Sig CO2 models or even the P320, there’s just not that much to see, although the P320 is close (internally). The M17, however, is an open book; remove the magazine and look up inside the grip and you have a clear view of the internal operating system, the opening for the rotary pellet magazine to fit in between the CO2 valve and the forcing cone at the back of the barrel housing, and the connecting valve that fits into the magazine’s CO2 chamber. All very straightforward in application and totally dependent upon the modular CO2 pellet magazine to operate.

There’s nothing hidden in here; with the slide held back and the magazine removed you can look right up into the grip and see the internal firing and CO2 mechanism. The 20-round pellet clip in the magazine fits into the opening behind the barrel (in the upper portion of the grip) and the connector between the CO2 in the magazine and the pistol fits into the valve that rests behind the magazine port. Once inserted the CO2 is ready to fire the DAO pistol.

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The M17 Magazine

This is the engineering marvel of the M17, a first-of-its-kind self-contained CO2 pellet magazine with a 20-round rotary fed “clip”. That’s the official term Sig Sauer has given to the modular pellet-loading device for the M17 magazine.

Loading CO2 is easier in the M17 magazine than any previous design. The articulated seating panel that extends back and down from the rear of the magazine allows easy insertion of the CO2 cartridge into the channel. The separate 20-round pellet clip can be easily loaded and locked into the magazine. Sig Sauer will have extra 20-round pellet clips available for sale in sets of 2 per package by December, making quick reloading of the magazines possible without changing out the entire magazine. Extra complete magazines with pellet clip will also be available. Prices have not yet been announced.
So here we are, loading Sig Sauer alloy pellets into the clip and ready to seat the CO2 in the magazine. The handle has been rotated upward and the CO2 cartridge is ready to move up and seat when you squeeze the handle closed…
…and this is all you do. Do it quickly, in one continuous motion until it locks. If you move too slowly CO2 will begin to escape as soon as the cartridge tip is pierced. You should barely hear any sound of CO2 when you close the lever.

Loading the CO2 into the large main section uses a long lever that folds down away from the back of the magazine housing. This is similar in operation to the loading system Sig Sauer developed for the P226 ASP, which had a folding backstrap panel to accomplish the loading and seating of the CO2 cartridge in one motion. With the M17 magazine, once the lever is lowered (as shown) the CO2 is inserted. You then raise the lever and squeeze it closed against the back of the magazine. In one move the CO2 is locked, raised into place, pierced and sealed with the housing that fits into the pistol’s grip frame. This is part 1 of the 2-step loading process.

The 20-round pellet clip opens up like the larger P320 magazine it is based on, and pellets are loaded into the belt chambers nose down. This is indicated on the housing of the pellet clip.

The pellets load into a compact version of the P320 rotary magazine; once loaded, the clip drops into a channel and locks into place. The CO2 and pellet clip are now one piece within the magazine and ready to load into the M17.

Once loaded, the clip fits into the front of the magazine. Press it in until you hear a click. That is the pellet clip locking into place…
…the pellet clip, CO2 and magazine are now all one piece and ready for business. The button on the front of the magazine, just above the extended base pad, is used to release the clip for reloading.

Sig Sauer will have spare magazines on the market before the end of the year and there will be two options, a complete magazine with 20-round pellet clip, or a set of 2 spare 20-round clips for quick reloading of M17 magazines. This is more efficient in terms of using up CO2 in one magazine, and a fine alternative to spending the money for a second complete magazine. For training, at least one spare magazine and clip would be recommended plus a set of extra clips for quick reloading of magazines during practice.

As you can see, the pellet clip extends above the rest of the magazine. This allows it to rest in front of the firing mechanism when inserted into the grip. The CO2 connector engages the valve in the action. Whenever you remove the magazine for reloading there is a brief hiss of CO2 as the magazine and gun disengage from each other, like removing a fitting from an air compressor hose.

First shots downrange

To wrap up Part 3, I am going to do an initial velocity test with the freshly loaded M17 magazine and Sig Sauer’s own 4.5mm, 5.2 grain alloy wadcutters. A run of 20 rounds at 15 second intervals (to minimize CO2 cooling and a drop in velocity) returned an average velocity of 353 fps, a high of 387 fps, and a low of 344 fps. This is well below the high factory spec of 430 fps, but that figure has an * followed by “Results may vary based upon pellet weight, temperature, and altitude”. Even so, 350 plus feet per second isn’t bad for a blowback action pellet pistol. And it is hard to make comparisons because there are no other pellet pistols that share this design!

In Part 4, I will chronograph a variety of alloy and lead wadcutter pellets in the M17 and run the first 10 meter accuracy test.

6 thoughts on “Sig Sauer’s new M17 Part 3”

  1. I hope it turns to be accurate enough and to the POA. That would be more than enough. As for the velocity I hope for better results from the Mauser rifled barrel version of this co2 magazine system I dream of.
    Nice weekend to you all.

  2. The way the pellet clip extends up above the rest of the magazine gives me some concerns about possible damage to the clip when inserting it into the gun.

    The Daisy Winchester MP4 pellet rifle (now discontinued) had a similar magazine design in which the dual ended 8 pellet rotary clip extended above the CO2 magazine. I think some owners reported damaging the pellet clip when inserting it and the CO2 magazine together into the rifle.

  3. The Sig pellet clip is very sturdy and the design of the M17 is so precise that there is no way for the clip to hit anything when being loaded. I have been testing it in and out of a tactical vest mag pouch and it is a tight fit, but no damage. Sig has built this two-piece magazine to be handled for training, so I wouldn’t worry about it breaking. And in the off chance it would get damage, the clip is easily replaced.

  4. If your initial Chrony results are with alloy pellets, lead pellets will barely make 325 fps making this a short range pistol. Was hoping to see this innovative design , provide higher velocity for more extended range shooting

    • I ran secondary tests with the Sig alloy pellets, two different M17 test guns and three different magazines and it appears the M17 will deliver 350 plus fps shots with the 5.25 gr. Match Ballistic alloy wadcutters. Given the excellent blowback action on this gun and its sound level, which I rate at medium loud, the CO2 is giving everything its got to run this gun and get the shots downrange. In Part 4, I will run tests with H&N Sport alloy pellets and two different lead wadcutters.

  5. Would expect about 10 percent less velocity with 7 gr lead pellets. Not awful , about what you get with co2 revolvers with 4 inchbarrel.. Where this type of co2 mag could hit higher velocity would be in a short barrel Carbine or a longer barrel 712 Mauser. Could then hit better than the published velocity for this pistol.

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