Postscripts Part 3

Postscripts Part 3

Air err and the Cowboy Lever Action

By Dennis Adler

A very good gun with more potential than almost any new model from 2018. Inadvertently, the Umarex Legends Cowboy can occasionally pierce only one of the two CO2 cartridges loaded when the piercing screw is turned down. This happened once for me, but has happened to several readers who tried out their new guns this past week. What I discovered is that even on one CO2 it will still send rounds downrange at better than 650 fps (and we’re talking alloy pellets from the Peacemaker pellet-firing cartridges, not steel BBs!) This means a special version like a Wanted Dead or Alive Mare’s Laig with cut down stock, 9-inch barrel and magazine would be possible and still shoot like the dickens!

“What we have here is a failure to communicate.” I’ve lifted this famous line from Cool hand Luke with the emphasis on cool because the air chamber in the new Umarex Legends Cowboy Lever Action is very cool, and in fact it needs to be re-explained and better understood. Traditional CO2 pistols and rifles use a single 12 gr. CO2 cartridge that fits in nozzle up (or horizontal on designs like the Diana Chaser and Cowboy Lever Action), but it is usually one CO2 to power the gun. When the seating screw is turned down, the CO2 nozzle pushes into the valve with its piercing pin and O-ring and the seal is complete.

As we know sometimes this fails, an O-ring wears out, was improperly installed, the piercing pin is not good, too short, breaks, all manner of things can go wrong, but rarely do. And most can be fixed.

But there is a problem. As you look into the air chamber on the Cowboy Lever Action you can see that this is a separate piece inside the stock, more than a valve that a CO2 cartridge seats against. It is a self-contained, polished air chamber that when filled with two CO2 cartridges and covered by the seating screw, becomes a closed system within the stock. The air from both CO2 cartridges is completely released inside this chamber which feeds air to the valve body in the receiver. If only one cartridge is pierced it will likely be the first (you can see the piercing pin at the front of the chamber) but the gun will still run at peak performance, just not for as many shots.

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To better understand how the Cowboy Lever Action works you need to look at the Umarex MP40 magazine which also uses two 12 gr. CO2 cartridges loaded back-to-back, just like the Cowboy Lever Action. The internal design of the MP40 magazine and the CO2 system in the Lever Action are essentially the same. You are loading the two CO2 cartridges with one nozzle facing into the CO2 chamber and the other facing up. When you tighten down the seating screw, the tube covers the nozzle of the CO2 cartridge and when tightened, forces both CO2 cartridges together pushing the first into the piercing pin at the front of the chamber while the piercing pin in the screw punctures the second. This releases all the CO2 from both cartridges into the CO2 chamber, which functions not unlike the air chamber in a precharged pneumatic pistol or rifle. A failure of one of the CO2 cartridges to be punctured only means that half the total volume of air is filling the chamber. The gun is still going to fire a peak performance because the air going into the valve system is a constant until there is too little air to allow a full charge. Thus you will get fewer total shots with only one CO2 pierced. The question is, “Why isn’t the second CO2 cartridge being pierced?”

While it is hard to see, the photo at left has one CO2 cartridge loaded, nozzle facing in, so you are seeing a little light reflecting off the bottom. The photo at right has the second CO2 loaded with the nozzle facing up and you are looking at the tip of the CO2 cartridge. There’s still a lot of space between there and the butt of the rifle.

I have discussed this today (Monday) with the Umarex technical department and there are several possible answers. First is that all CO2 cartridges are not exactly the same length. In a CO2 pistol this is rarely a problem because the seating screw has an ample margin for length when being tightened. In the Cowboy Lever Action it is a very precise fit and when you turn down the seating screw it only goes so far and you cannot tighten it any further. The two CO2 cartridges should be pierced by that point and the chamber filled with the CO2 from both. Now, if there is a variance in the length of the CO2 cartridges one might not be long enough for the two 12 gr. cylinders pushed back-to-back to be fully pierced by the top piercing pin. That is one possibility, and let me say this right now; Umarex does not recommend placing any object inside the chamber between the two cylinders to act as a spacer and create a tighter fit. You would be placing a foreign object inside an actual pressurized air chamber, not just between two CO2 cylinders.

The second possible problem is one Umarex began investigating which is piercing pins that may be too short or not sharp enough to pierce both cylinders when the chamber cover is screwed down tight. This could be a random problem as it is not happening with every lever action model that has been sold and has not occurred at Umarex during product testing. I have already tested three rifles and only one exhibited the problem.

At this point, after an odd mix-up in deliveries, I have three Cowboy Lever Action rifles on hand, and I am going to load all three, fire them out and then inspect the CO2 cartridges for piercing. I am going to use Umarex CO2 cartridges which are made to Umarex standards and should not be part of the problem (but my failed CO2 piercing with the gun used in Saturday’s article was loaded with Umarex CO2).

While I have been writing this today, the Umarex tech staff has been running tests on six randomly picked off-the-shelf Cowboy Lever Action rifles and none had a failure to pierce both CO2 cartridges. And they have a fix for the problem that should work most of the time unless there is a defective piercing pin. What they suggest is to use a drop of RWS Chamber Lube, not only on the tip of the CO2 cartridges but directly on the green O-ring on the seating screw (as shown in the pictures). If the ring is dry it will stick and not allow the screw to turn down as far; this could be the cause of the random problem.

The seating screw is a long chamber that fits over the top of the second CO2 and has its own piercing pin. When the screw is tightened down it forces both cartridges together with the front being pierced by one pin and the second by the pin in the seating screw. The large green O-ring seals the chamber as all of the air from both cartridges is released. Umarex recommends putting some RWS chamber lube around the green O-ring before turning it down. This will allow it to screw down tighter and assure both CO2 cartridges are pierced. I tired it and it worked every time.

I am starting with the second off-the-shelf Lever Action I received. I will load it with Umarex CO2, and use RWS chamber lube on the green O-ring before tightening it down. Going on the assumption that both CO2 cartridges have been pierced, and since I have to shoot it out, I thought I might as well chronograph again with a new rifle and the silver pellet-loading shells with H&N Sport Match Green 5.25 gr. alloy wadcutters.

I set up 25 feet from the target for the chronograph test. Average velocity was very consistent to previous tests at 661 fps with H&N and the majority of shots at 660 fps to 663 fps for the first 20 plus rounds. At the distance of 25 feet my best 10 shots were in two 5-shot groups measuring 0.43 inches in the bullseye and a second group, aiming below the bullseye, measuring 0.50 inches. Now, after that I kept shooting to count shots until empty. I stopped after 40 consecutive shots and chronographed the next 10, which averaged 628 fps. From there I shot until I could tell there was a drop in sound and power of impact on the target, at which point the total number of shots was 70. I ran one last chronograph test and shots were clocking 453 fps average. I got another 21 rounds out of the CO2 until empty, which is much further than one would normally go for any kind of accuracy, but I wanted to know what two pierced CO2 cartridges could deliver and that number appears to be 91. I unloaded the CO2 and both cartridges were cleanly pierced.

This is the rifle that had originally failed to pierce both cartridges and this time with the chamber lube I got two more turns on the piercing screw before it wouldn’t turn further. After shooting it out I found both CO2 cartridges had been pierced.

The second test with another off-the-shelf gun gave a total of 89 shots until empty and again both CO2 cartridges had been pierced. To prove the Umarex theory of using the RWS chamber lube on the green O-ring, I ran the final test using the first rifle that had failed to pierce both CO2 cartridges.

Again I used the RWS chamber lube before tightening down the piercing screw. I can recall that in my previous tests with this first gun there was a point at which the piercing screw would not turn any further and I believed it was down as far as it could go. Since loading the other two rifles I found that there was a little more turn down in the screw than I had experience before, but I attributed this to it being a different gun, but this is not the case. I was able to turn the screw down another two turns with the chamber lube on the green O-ring. With this same gun from my previous Postscript test I was able to get a total of 97 shots. I chronographed shots 71, 72, and 73 at an average velocity of 528 fps. The gun failed to fire on shot 98. Opening the CO2 chamber I found both CO2 cartridges were fully pierced.

With a new test gun and using the chamber lube on the seating screw the gun clocked an average of 661 fps with H&N 5.25 gr. alloy wadcutters fired from Peacemaker pellet cartridges. Shooting at 25 feet from the target through the chronograph I placed 10 shots into two 5-shot groups measuring 0.43 inches and 0.5 inches. The total number of shots from this gun was 91, though I would quit somewhere around 70 rounds to assure a respectable velocity.

So, the trick if you find yourself running out of air too soon and discover you have only pierced one of the two CO2 cartridges, is to not only put a drop of chamber lube on the tip of each CO2 as usual, but a drop on the green O-ring and make sure it is oiled all around its circumference before tightening it down.

Here are the two pierced CO2 cartridges from the second test gun. If you look at the head of the seating screw you can see the piercing pin inside. It takes a full turning down of the screw to pierce the second cartridge. Lubricating the green O-ring assures this will happen.

The Legends Cowboy Lever Action might not have qualified as a candidate for Replica Air Pistol of the Year in 2018, but it certainly gets my vote for CO2 air rifle! Now if they can make a Mare’s Laig it can win Pistol of the Year some day!

We now return you to our regularly scheduled programming….

25 thoughts on “Postscripts Part 3”

    • Sadly, all this talk of a Mare’s Laig is just between us guys; I don’t think Umarex is going to do anything more with the Cowboy Lever Action since it just came out. I would expect a weathered finish next, since it is already being offered in Europe. As for another version, it will take time and a market large enough to justify new tooling. I think, and this is just me, that in America and in a good part of Europe where American TV Westerns were watched by young boys as avidly as here at home in the 1960s, “Wanted Dead or Alive” is a classic, and if any one variation of the Lever Action would sell universally that would be it. I plan on making a recommendation to Umarex after the Shot Show, for future product planning, but as you know, as we all know, every new gun, every change, takes a long time. Let’s see what is unveiled this month at Shot Show. Might give us an idea what will be out later this year and early next. As for an extended capacity mag for the M712, it never existed in real world design, so very unlikely in CO2.

      • Can RWS Chamber Lube and Pellgunoil be used interchangeably?

        I have both, but I mostly use Pellgunoil on the heads of the CO2 cartridges. My concern is if the O-ring material is not compatible with Pellgunoil.

        As you said about possible new products, every company has to balance investment costs with potential market sales. I’ve been thinking that a pellet shooting replica of the Thompson submachine gun would be a home run for Umarex, just as the MP40 replica was. Nevertheless there’s still no pellet shooting replica Thompson available unless you want the one from SMG (I think) that has the big air bottle attached to the base of the grip.

        On the other hand, the new 0.22 caliber Sig MCX Virtus PCP pellet rifle might prove to be a big seller.

        • I think everyone believes a Thompson would be a home run, and if anyone is apt to do it, probably Umarex at some point because of the technology used for the MP40. I wish everything we as airgun enthusiasts would like to see could come as swiftly as our desires, but this is a business that moves very slowly due to manufacturing costs and marketing demands. The Thompson, though, would have been perhaps preferable to the MP40 in retrospect as having been one of America’s great designs. And speaking of great designs, the forthcoming Sig Sauer models for 2019 will be very satisfying to everyone.


          • Do you have an answer for my question about the compatibility of the o-ring with Pellgunoil? What does Umarex say?

      • The Mare’s version is a long shot , but the Walther version was made in a short barrel , large loop Duke version. Since Air Venturi has been offering Duke Peacemakers, why don’t they have Umarex make a Duke weathered finish 18 inch large loop version of the1894? Regarding the hicap 712, this is a part fantasy market, so why not?

        • Ah, it is a lot of fantasy, I agree. I’m not aware of any higher capacity Mauser Broomhandles than the 20-shot models, but as I am sure you know, Luger had a drum magazine for the Navy Model and several other Luger 9mm Parabellum versions. I think we all have a fantasy gun we would like to see in CO2, among mine would be the Model 93R Beretta, which most ironically is made in an Airsoft model. I am told that ASG will not have much new to offer in CO2 for 2019 as this will be a year with more emphasis on Airsoft models. What is the general consensus among Airgun Experience readers about Airsoft models? Any interest?

          • Airsoft is high tech spitballs. Sad to hear ASG is not offering anything new in metal projectiles. A shame, since the Dan Wesson 715 was the best of the da revolvers. Was hoping 2019 would be better than 2018.

          • I will admit that I nearly purchased a full auto airsoft version of a Thompson submachine gun after seeing a video of it in action. However, those mandatory orange muzzle tips and the airsoft guns made of translucent plastic are a real turn-off. Despite all other working features, the orange tips alone says to me that airsoft is not a true replica.

            I also don’t want to have to start stocking other gases besides CO2 to power airsoft.

            So put me down as not interested.

  1. I’ve recently read that Air Sig is bringing out a New “Super Target” airgun pistol in .177 for 2019, a single stroke pneumatic……hoping you get a look at it and can comment.
    Posting here because no other format available….???? Receive my new Crosman 2300T tomorrow. going to try my hand at 10 Meter…


    • Chuck, yes they are and it is a P226-based exterior design built around the Italian (Chiappa) made FAS 6004. This will be a very accurate single shot pellet model and as soon as Sig has a test gun we will have it covered in Airgun Experience.

  2. Thanks Dennis for all that work.I shall be liberal with the lube!!
    It is really useful to have a new product introduced with a direct line from the users getting used to the equipment and to the manufacturer. We are at the bottom of the learning curve.
    Incidentally you might mention to Umarex that the availability of spares in the UK has taken a dive since Armex lost the contract and it will put people off purchasing Umarex guns if they cannot get them repaired.

  3. Dennis, enjoy the Shot Show next week and bring us all the new Airgun info…
    Re Airsoft, I am old school and grew up with BB and Pellet…
    i consider Airsoft to be Gamer guns, just never got into them and most likely never will…
    Thanks for the Air Sig “Super Target” info…it looks just like a FAS 6004, I don’t see any Sig 226 at all…???
    Will be interesting to hear from you coming from the show, looking forward to it…


    • Not sure what you have seen but the Sig version has a distinctive look from the FAS 6004. As for Shot Show that’s Tom Gaylord’s annual gig, but Im in contact with all the manufacturers so we will be getting the latest guns to test for Airgun Experience as soon as samples are available.

  4. This is a copy from Sig’s new 2019 Catalog<img width="510" height="364" src="/airgun-experience/wp-content/uploads/2019/01/fas-6004-pellet-pistol-551.jpg" class="attachment-large size-large" alt="" srcset="/airgun-experience/wp-content/uploads/2019/01/fas-6004-pellet-pistol-551.jpg 900w, /airgun-experience/wp-

    • Chuck

      There is a similarity dictated by the functional design, and while it is very similar to the FAS the Sig Sauer Super Target still has its own distinctive style about it. I hope it is as accurate as the FAS 6400. I think from a combat shooting perspective the Sig is more interesting with the grip shape, triggerguard, and sight design. Looking forward to testing this one.


  5. I loaded CO2 into my Cowboy Lever Action again yesterday. The cartridge that did not pierce the first time I inserted first into the chamber so that it was the cartridge nearest the trigger. I used Pellgunoil on the tips of the CO2 cartridges. Then I applied RWS Chamber Lube to the o-ring before screwing the seating screw into the chamber. I screwed it in until it wouldn’t turn any more. Attempts to get additional turns were causing the stock to twist so I stopped.

    Once again I only got 50 shots. After I removed the screw, I saw that the back CO2 cartridge that was pointing up had been pierced. However, the front CO2 cartridge was not pierced, and this was the same un-pierced cartridge from the first time. I compared this un-pierced CO2 to a new CO2 from the box and could not see any difference in appearance. What that suggests to me is that the un-pierced CO2 had not made any contact with the piercing pin. If the un-pierced CO2 cartridge had at least made some contact with the piercing pin, I expected to see some sort of “dimple” pressed into the head of the cartridge, but I saw nothing like that.

    You mentioned that CO2 cartridges could possibly vary slightly in length. Could they also vary slightly in diameter enough that a cartridge could be too wide and become pressed against the sides of the chamber thereby preventing the cartridge from reaching the piercing pin?

    I’ve tried looking down the chamber at the piercing pin, but I can’t see it well enough to see if it is too short or damaged. My next step is to measure several CO2 cartridges to see if indeed there is enough variation in size. I may also try some Crosman and Swiss Arms cartridges that I have. Maybe I didn’t use enough Chamber Lube on the o-ring.

  6. Well, I think I found the problem. When I carefully inserted my 0.177 caliber cleaning rod into the CO2 chamber, I discovered that the front piercing pin is not protruding into the CO2 chamber. My cleaning rod slide right over the piercing pin without encountering any obstruction from the pin.

    • Yes, this sounds like a problem with the piercing pin either being too short or not sharp enough because the front cartridge should always be pierced. All the force when tightening the seating screw is pushing forward and if there was going to be an issue with piercing it would be the back CO2 not the front. The two failures I had with the Lever Action were with the second CO2 not being pierced because the screw had not been turned down enough. This sounds like a mechanical issue and needs to go back to Umarex or PA for a fix or replacement. So far with all the tests and the tests that were done to answer the initial problem at Umarex USA, it seems this one is a different problem. It happens, you just drew the short straw, or short piercing pin as the case may be. On the flip side of this is the fact that you have proven, as I did with my similar problem, that the Lever Action will still hit maximum performance on one CO2, just fewer shots. If you got 50 on one then my estimate of 96 with two working is right on the money. You always analyze everything correctly, so I have no doubt that this is a failed piercing pin. Hope you get your replacement back quickly and get back punching bullseyes.

  7. Nearly a month now with the Lever action. One blocked barrel with an irregular BB and no other problems. Prefer using pellets to BBs. Starting counting in 11s. Getting use to the lever action so few jams. Accuracy all I can demand from iron sights.
    Great stuff well done Umarex.

  8. We are clearly going to be using these shells more. New shells tend to be a bit tight but equally they will wear out gradually. Has anyone actually worn out a shell. I have never seen replacement inserts offerred as spare. It will be a shame to have to throw out perfectly good shells because of insert wear.

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