Mendoza RM 2000: Part 2

by B.B. Pelletier

Part 1

Okay – back to business. When we last looked at the .22 caliber Mendoza RM 2000, we saw the beauty of its adjustable sights and the marvel of the magazine loading system that enables this breakbarrel to be a repeater. Let’s look at velocities and some necessary preparatory maintenance.

One of our readers wrote a comment that his RM 2000 got about 500 f.p.s. with 15.8 JSB Exact pellets. The description on the website says the gun gets “…smashing velocities up to 850 f.p.s. in .22 caliber.” Of course that would be with lightweight pellets, but I would expect around 700-750 with .22 caliber Crosman Premiers and somewhere in the mid- to high 600s for the JSBs. That said, let’s see!

Velocity
The first pellets I tried were the Premiers. They averaged 713 f.p.s. with a spread of 38 f.p.s. The rifle is still producing a lot of smoke on every shot, so this wide variation is due to excess fuel burning in the compression chamber. If you wonder what that means, read the recent 3-part post about dieseling. This velocity is on the low end of what I expected from the stated velocity provided by the manufacturer. Going next to the 15.8-grain JSB Exacts, I got an average of 643 f.p.s. with a spread of 54 f.p.s. Again, this was slightly below the expected velocity, and the spread pointed to fuel-burning.

But, the real shocker came when I tried 11.9-grain RWS Hobbys. I expected to get up into the 800 f.p.s. realm, or at least close to it, but instead the average was only 726 f.p.s. That’s only a little more than the heavier Crosman Premiers! However, the extreme spread was down to 35 f.p.s., indicating the rifle likes this pellet better than the others – or at least that’s how I read it. The last pellets I tried were 21-grain Beeman Kodiaks. To my surprise, they averaged 618 f.p.s., with a spread of 34 f.p.s. The gun vibrated noticeably with this pellet, so I think there is some piston bounce, but look how close in velocity they are to the 15.8-grain JSBs. That tells me I need a better fitting pellet in about the same weight as the JSBs, because they obviously don’t fit the bore well.

Dirty bore!
All shots were loaded single-shot, because most of these pellets will not feed through the magazine. I resolved to test some Premiers through the magazine for you, as well. Unfortunately, when I was blowing the smoke out of the barrel during testing I happened to look through it and, for the first time in my life, I saw a dark airgun barrel. Usually darkness is a sign of smoke remaining in the barrel, but that wasn’t the case this time. This barrel was dirty in a very visible way! I had forgotten to clean it with JB Non-Embedding Bore Cleaning Compound, like I have been lecturing you for over a year. So, everything stopped while I cleaned the barrel.

What a lesson!
This was the most difficult airgun barrel I ever cleaned! The brush just didn’t want to go through the bore. Boy am I glad I have a Dewey one-piece steel cleaning rod, because I think the effort would have broken a three-section aluminum rod. Up to pass number four, the force needed to push the rod through the bore took all my strength. The brass brush bent at the breech several times, so great was the entry force required. After pass number four, it became slightly easier, but I was able to feel a rough section just a few inches in front of the breech. That feeling went on until pass number 15, when everything smoothed out and became light and easy. I wish I owned a borescope, so I could look at these new bores and even take some pictures before cleaning them, because the feedback I get from the rod tells me they really need the cleaning!

Performance after cleaning – another lesson!
Crosman Premiers were first to be tested, and what a lesson they taught me! Velocity ranged from a low of 622 f.p.s. to a high of 832! Yes, nearly 200 f.p.s. spread. The median shot hovered around 724 f.p.s., so not a lot of change. BUT, when I loaded them through the magazine, the velocity was always higher and more consistent. That suggests that the Premier is too small for the bore of this rifle and it needs the extra resistance of squeezing through the end of the moving shuttle/breech to generate power.

Having established that, I figured fat pellets would be the best medicine for the RM 2000. RWS Super-H-Points are medium weight at 14.2 grains, but they have a wide skirt. Maybe that is why they gave a velocity of 754 f.p.s. with a spread of only 18 f.p.s. Beeman Ram Jets, on the other hand, are heavier, at 14.8 grains, but not particularly wide. They averaged just 670 f.p.s. with a 43 f.p.s. spread. Not the pellet for accuracy in this gun. Hobbys went an average of 724 f.p.s., which was a little slower than before but they only had a 25 f.p.s. spread – down 10 f.p.s., which is significant.

What have we learned so far?

  1. The RM-2000 likes fatter pellets.
  2. Crosman Premiers feed well through the magazine.
  3. The Bug Buster 2 scope cannot be mounted if you want to use the magazine.
  4. The RM 2000 is well-lubed from the factory.

Now that the barrel is clean and I have a good handle on which pellets to use, we’ll try accuracy next.

24 thoughts on “Mendoza RM 2000: Part 2

  1. Regarding the bore cleaning:

    Wouldn’t it be easier to put the cleaning rod (without the brush) through the muzzle down to the breech, and then attach the brush? During the cleaning pass this would put the rod under tension rather than compression, which would eliminate the risk of bending the rod. Same principle would apply to bending the brush, I think. Is there a particular reason you did it that way, am I missing something painfully obvious?

    -Stuart


  2. Stuart,

    Good thinking, except that the brush comes all the way out of the barrel at either end. So doing it your way requires turning the rifle around 40 times and screwing the brush on 40 times. That would take too long for me. However, since the brush got easier at 15 passes, the total number number of removals and installs might just be 30 times instead of 40, with the final five two-way passes made the conventional way.

    I never faced this problem before, so I suppose I wasn’t thinking. Perhaps your way is better.

    B.B.



  3. BB, you say that there may be some piston bounce in the mendoza,when you shoot beeman kodiaks through it ,is there anything you could do like make the piston heavyier to over come this,or would that have diverse results when light pellets are used,i no manufactures sometimes under weight ther pistons,is there a solution to this


  4. nathan,

    I’m not sure that piston bounce is the reason for the vibration, but whether it is or not, careful tuning could make the gun perform differently. I would install a heavy tophat weight in the piston to increase mass.

    But until I know what the most accurate pellet is, I wouln’t do anything.

    B.B.


  5. B.B. Please explain why a dirty bore affects fps. Is it simply that the “plaque” in the bore actually restricts free pellet travel? Don.



  6. hi bb
    sorry about all the questions but i dont have much experience with scopes. is a leapers 6-24×50 too big for a hw50? by too big i mean will it interfere with loading or cocking? would a 4-16×50 be a better choice? thanks
    Nate in Mass


  7. Nate,

    The 6-24 could be too long for the HW50. I think the 4-16 is a safer choice. And even that scope will almost overpower the 50. I would think a 4-12 might be ideal as a big scope for that gun.

    B.B.


  8. thank you
    i was thinking the others were too big. can the 3-12×44 take a paralax sidewheel? also should i use high or meduim rings?
    Nate in Mass


  9. Nate,

    There are 4 3-12 X 44s and I think they all can take the optional sidewheel.

    I would call and ask customer service about the right mount height, depending on which of the 4 you select, because there are two different outside diameters. And don’t forget, you need 30mm rings, not one inch.

    B.B.



  10. Hey BB

    Have you heard about the new gamo whiper? If so what do you predict it to be like? Oh and BTW whats a fluted polymer bull barrel? Is the barel made of some sorta polymer synthetic.

    Thanks, Kyle.


  11. I recently purchased a Beeman 5039 (high, 1 piece) scope mount. I noticed I sometimes miss a target left or right if the scope is slightly tilted. I was looking to get a bubble level to remedy the situation. I have a Diana model 48 with their tiny usless scope rail so the mount takes up all the room on the rail. I see you guys offer the Beeman spirit level but it says it will only fit the 5040 (medium, 1 piece) and a few others. I believe the only difference between the 5040 and the 5039 is the height, both are for 1″ scope tubes and look very similar. Would the spirit level not work on the 5039 as well?


  12. Crosman pellets,

    I sure don’t know when they will be available.

    The British firm that made some of these pellets before Crosman was putting out horrible quality, and Crosman wants to bring quality up to their high standards before they bring them to market. I tested the hollowpoints years ago and you couldn’t hit the wall of a room shooing from inside!

    B.B.


  13. Kyle,

    The Whiper? Is that Whisper? No, I’ve heard nothing.

    A fluted polymer barrel is what the marketing department who doesn’t know diddly about guns calls a steel barrel with a plastic jacket. The flutes refer to long scallops that would remove weight from an all-steel barrel. In plastic they just look cool.

    B.B.



  14. BB

    Sorry that was supposed to be whisper. Apparently it has some sort of suppressor (is this like a shrouded barrel?) to reduce noise. Just wondering if you heard or not. I saw it on gamousa’s home page.

    Kyle.



  15. Kyle,

    Not only do I know it – I have been seeing it for the past 2 years at the SHOT Show! Sorry I didn’t make the connection earlier.

    Everyone who saw it thought that the reason Gamo didn’t bring it out in 2006 was because it has a baffled silencer in that shroud. But the TX 200 has had the same thing for many years, so that can’t be the reason.

    If I get the chance, I will test one.

    B.B.


  16. It would be great, B.B. if you made it a policy to not answer any questions that deviate from the model you are reveiwing. As a new, prospective air gunner, I am tired of reading about a load of other rifles on a forum that has nothing to do w/ those rifles. My 2 cents. Thanks


  17. Nooftie,

    Interesting view.

    The main reason I like this airgun site better than the 6-7 others that I frequent is the ability to have an exchange with airgunners (and B.B.) about any topic airgun related. The comments may or may not be related to the article that B.B. wrote that day.

    There are some days that my only interest is in the article that B.B. has written and I gloss over or even ignore the comments. I must say though that most of the time the comments teach me as much about airgunning as the articles.

    Sure nice to have the option though.

    If you're only interested in reading the comments/articles relevant to your interest you may want to use the search box since it will filter all unrelated items.

    kevin



  18. This question needs to be directed to the Techs at Pyramyd Air. They may have what you need.

    I will ask my wife to ask them, if you will post your question to the current blog:

    B.B.


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