Author Topic: RM2003 - my first diesel powered rifle! (part 1)  (Read 6817 times)

Offline vinceb

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RM2003 - my first diesel powered rifle! (part 1)
« on: August 05, 2007, 01:56:49 PM »
Yes, yes, I know that some tout diesel power as being one way we can save energy - but frankly, this is carrying it a little too far!

However, I'm getting ahead of myself. So I'll start at the beginning.

I found myself with some disposable change in my pocket, so I inevitably started sniffing around for some way to toss it out the window. Despite the wonderful experience I've had with my RWS48, I've still got this thing against the cost of a typical "good" airgun... after all, why buy ONE that I know I'd be happy with when I can by 2 or 3 that are questionable?

In any event, one gun that always sorta tickled my curiosity was the dual-caliber Mendoza. All I knew about it was that it had intercangeable barrels of some sort and a really interesting peep sight. The scuttlebutt on this gun wasn't all that good, however... so I decided to find out for myself by ordering a $133 refurb from Umarex.

I placed the order on a Tuesday, and the gun arrived on Friday as expected. It wasn't packaged nearly as well as the RWS48 I had gotten a few months ago, perhaps this only mirrors the packaging done by the factory. The rifle itself was none the worse for the trip, but because it wasn't packed in a plastic sleeve, some styrofoam bits worked their way into the guts of the gun. I was able to pick out all the ones I could see.

The overall look of the Mendoza was a bit of a disappointment, especially with regards to the stock. The shaping is a little rough, having a slightly "hand carved" appearance to it and something of a grayish tint to the brown. The feel of it is OK, but a little hand-refinishing would do wonders for it.

As for the metalwork - well, the finish on the compression tube isn't bad at all, but it is certainly better than the barrel. Unfortunately, however, Mendoza seems to use a rather course "dot matrix" engraving method (rather than stamping) when they need to emboss something into the metal (like the serial number). No doubt it is an automated process, but it looks cheap.

The muzzle on this gun has to be one of the coolest-looking muzzles on any air rifle with a hooded fiberoptic sight, a small muzzlebrake, and the release latch for the barrel change mechanism. The rear sight is to die for... an all-metal dovetail-mounted peep sight (you can move it closer or further away to change the apparent size of the apeture) with fine adjustments and solid detents. There's no free-play to speak of. On the RM2000, the same mechanism is used to mount a standard open-iron sight. Either type could be considered to be the "holy grail" of inexpensive airgun sights... and it puts virtually every other low-priced sight to shame. Gamo, Crosman (especially), even RWS - I don't think ANY of them can hold a candle to this one.

The gun also has an automatic safety, which (unfortunately) isn't mounted in the trigger-guard area. There's a little buttoned lever on either side of the end of the compression tube, it's a little awkward to use but not too bad. It is resettable (unlike the B20/B26). The trigger itself in an interesting affair... it has 2 blades that control 2 separate sears. One blade sits forward of the second, and both have to be pulled in order for the gun to go off. The overall pressure required is pleasingly light, and this unusual arrangement really doesn't feel all that strange in actual use. The trigger isn't quite as nice as my RWS48's TO5, but it is an improvement over the Gamo trigger, for example. There doesn't seem to be any adjustment for it, and in this example there is none needed.

The barrel change mechanism is nicely done. Pull the release latch back, unscrew the muzzlebrake, and the insert slides right out. Slide the new insert in and reinstall the muzzle brake, and you're done. The brake itself doesn't tighten against the insert - it has a short and stiff spring that does that. At the other end of the barrel the insert does protrude a little, and when you close the breach this mates directly with the transfer-port face of the compression tube, with the spring pushing it home. There's no other seal, and the end of the barrel insert eventually wears nice'n shiny as it breaks in.

It's a simple and elegant arrangement, but there's some potential problems with it. First of all, it's hard to imagine the seal being as perfect as a good soft seal would be. Second, will it wear the compression tube mating face down? Lastly, how long will it be before the barrel insert wears down to the point where there's no more spring tension on it? Unfortunately I can't answer any of these questions, but these are things to keep in mind when considering this rifle.

Cocking the gun is a bit of a surprise. It has a short stroke, which necessitates a high cocking effort. Reminiscent of a Daisy Powerline, although I don't think it's quite as stiff as that (or as an MP513). But certainly high for the power level. The cocking cycle is a bit rough, and between the cocking and closing of the breach it definitely has a cheap feel and sound to it.

The compression tube has a oil hole in it through which you can see the piston, and Mendoza came up with the clever idea of painting the front of the piston red. This means that the oil hole does double-duty as a cocked indicator - if you see red, the gun is cocked. At first I thought that this was merely a clever gimick, but as I shot the gun more and more it decided I really liked this feature.

The breach pivot - well I haven't quite figured it out yet. It seems to be held in by a pressed-in pin, rather that the more typical bolt... so what happens if the pivot wears? Will it develop side-play that is impossible to remove (easily)? Or does it have some sort of spring-loaded washer that will keep it tight for many years of use? Again, I can't answer that question.

Well, eventually it came time to actually fire the gun. And this is when I discovered (not unexpectedly) that it was "all fueled up and ready to go"! It dieselled - a LOT - and I believe it even sent a .22 Crosman Premier supersonic on one shot! When I tried shooting it over the chrony, I got an extreme spread of close to 300fps! After about 300 shots or so it FINALLY started settling down (somewhat), and I was able to get what I believe are representative figures for velocity.

In .22 cal it seems to do around 600fps with Gamo Hunters, around 620 with Premier HP's, and 640 with Gamo Match. I switched over to the .177 barrel, and am getting around 820 with CPL's, 830 with Gamo Match, 840 with Hunters, and 860 or so with RWS Diablo Basic (Geco) pellets. Since velocities were still not terribly consistent, these numbers are strictly "ballpark". So - surprise! - the factory velocity claims are horse-poop. And I'm sorry, but the dieselling shots don't count (even if they DO provide an oil hole!)

Needless to say long-range accuracy suffers while the velocity is jumping around so much, which is why I won't talk about it much just yet. I will offer one observation - at 60 yards, changing from one barrel to the next resulted in a very significant POI change in the vertical direction (as expected) - but hardly any in the horizontal. The vertical change is unavoidable, but the consistency in windage would indicate that this barrel insert arrangement is fairly well made. Still, if it doesn't shoot at least as well as other comparably-priced guns, no number of gimicks will make this a good rifle to buy.

To be continued when I can document its accuracy, and I'm planning to post some pics at that time.

Offline PeakChick

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RE: RM2003 - my first diesel powered rifle! (part 1)
« Reply #1 on: August 05, 2007, 02:17:44 PM »
Nice first impression review Vince. I think a lot of us are curious about the Mendozas. Keep us up to date as it gets broken in.
The current stable, (arsenal, quiver?): BSA Lightning XL .177, BSA Sportsman HV .22, BSA Ultra .177, CZ634 .177, Daystate Harrier X .177, TAU 200 Senior .177, HW 97 .177, HW 50s .177, HW 30 .177, RWS 92 .177, Gamo 126 MC Super, Gamo Big Cat .177, AR2078A, QB78 .177, Quest 1000 .177, Beeman SS650 .177., Beeman P17 .177.

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Offline shadow

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RE: RM2003 - my first diesel powered rifle! (part 1)
« Reply #2 on: August 05, 2007, 02:21:13 PM »
Well Vince thank's for the first review on the duel cal.. Sound's like a lot of mystery machining in her and I was also wondering about the POI between cal. and barrel's. Great review and we'll keep our eye's peeled for your next one with pic's. Ed
I airgun hunt therefore I am... };)  {SHADOWS Tunes & Camo}

Offline Big_Bill

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RE: RM2003 - my first diesel powered rifle! (part 1)
« Reply #3 on: August 05, 2007, 05:29:05 PM »

Great review Vince,

I wondered how these inserts were locked in !

They seem to have gone to some expense on this system, much more than I expected.

I look forward to your continued review on this rifle.

Thanks for sharing your findings with us.

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Offline Gene_SC

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Re: RM2003 - my first diesel powered rifle! (part 1)
« Reply #4 on: August 05, 2007, 11:54:04 PM »
Great review there Vince. My biggest gripe about the duel barrels is when using a scope it would be quite inconvient for re-adjusting the scope everytime you changed barrels. You have brought up some very interesting points and can't wait to see a further detailed review of what you find and you overall opinion..

Thanks for sharing Vince
THE ONES I SLEEP WITH: BSA Lightning XL, AA TX-200, AA ProSport, BSA Ultra, HW-97K, Crosman NPSS .177, FX Cyclone, HW-30 Nicle Plated, AA-S200, Crosman Marauder, CZ-634, R-9 DG, Webley/Scott UK Tomahawk, Benji Kantana, Benji Marauder, Benji Discovery.....

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Offline davee1

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good job Vince....
« Reply #5 on: August 06, 2007, 03:33:00 PM »
Well said!!! Yep, I really wonder how long it will take for the barrel/air transfer port to show some wear.  Can't possibly seal properly without an oring there, and there's metal-to-metal contact going on.  And the deisling...mine still does that.  It's a cool lookin' rifle that feels comfortable, is well balanced, and has a really good sight.  I guess if we could do something about that seal, then we might have a neat rifle on our hands.
Walther Falcon.25, Shadow.177, Shadow Express.22, Whisper.22, CFX.177/.22, B3AK.22, B3.177(x2), B4.22, B21.22, B26.22, Diana350M.177/.22, Beeman1073.177/.22, Hammerli Storm.22, Hammerli X2.177/.22, BeemanP1.177, P3.177, P17.177(x2), Diana5G(P5).177, Diana LP8, Browning800, BenjiHB22, Crosman1377, Marauder.22

Offline vinceb

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Took the Mendoza apart...
« Reply #6 on: August 10, 2007, 12:38:34 AM »
It seems to be fairly well made inside. The spring is massive and has tons of preload.

Surprisingly, there wasn't a lot of lube inside... but the piston seal seems like a rather loose fit inside the compression tube. This (of course) means that oil won't be scraped away during the cocking stoke. That might also explain the low power.

I think I'm gonna try getting a new seal for it.