Author Topic: Part 2 on the Mendoza RM2003....  (Read 6642 times)

Offline vinceb

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Part 2 on the Mendoza RM2003....
« on: August 17, 2007, 12:45:47 PM »
Well, I've finally spent enough time with the Mendoza 2003 (inside and out) to finish my review.

When I first got it, I put a few hundred rounds through it in an effort to get it to stop dieselling. No luck. Consistency was, of course, not very good - either from the standpoint of velocity or long-range accuracy. So I stripped it down, cleaned it out, deburred the holes and slots in the compression tube, and inspected the piston seal. Everything seemed to be in order, so I put it back together and lubed it with a combination of 30wt oil and (about 20-25%) moly powder.

After putting it back together two or three times (I had a little trouble with that!) I was ready to put it through some more "formal" testing.

Dieselling was reduced considerably, and it was largely gone after the first couple dozen shots. And it showed in the velocity results... which were now both more consistent and lower. I only tested the velocity with Gamo pellets (I don't have a wide variety of pellets, and Premiers didn't work too well in this gun) - but the results were in line with what I sorta expected. In .177 caliber, the rifle shot 7.5gr Gamo Match pellets at about 780fps. In .22, the same pellets did about 615. That's about 12ft-lbs in .22, and only about 10 in .177. I also tried Hunters (15.4gr) - they did about 580, which shows a little less energy than the Match pellets. I DID have a stray diesel shot that sent a Hunter out the barrel at 846fps - and now we know how Mendoza got that 850fps rating in .22!

Earlier I mentioned how this rifle doesn't have a breach seal, and I wondered if that might be causing a loss of power. The barrel insert is held in place by a spring under the muzzle cap, and when the breach is closed it is pushed back against the transfer port mating face on the compression tube. The end of the insert eventually wears in, becoming very smooth and shiny in the process (see picture #1). To find out if this metal-on-metal seal was leaking I tried the old wax paper test - and found no sign of leakage with either barrel. And (so far, at least) there is no sign of wear on the compression tube mating face... so it appears that Mendoza's arrangement does the job.

Changing the barrel is both fast and easy. It can be done with the breach open or closed and the rifle uncocked or cocked (why would you want to?), and requires no tools whatsoever. The second picture shows the muzzle of the gun when it is assembled (ain't it a cool looking muzzle?). To change the barrel, one pulls the lower knob rearward to release the ratchet and unscrews the muzzle endcap. The third picture shows the endcap removed, and the barrel insert partially slid out. If it takes you 30 seconds to change barrels, it's only because you are taking your time!

The fourth picture shows the dual triggers, an arrangement that works surprisingly well. There is very little tension and virtually no friction on the front trigger, but it has to be pulled to the rear before the gun will fire. The second trigger has very little creep and a pleasingly light pull to it. When I had the gun apart it was obvious that this simple mechanism is a cheap one to manufacture... but it works far better than one might expect.

The last picture shows the rear of the compression tube, the location of the automatic safety, and that wonderful peep sight. I can't say enough about that sight... I wish I could have one on every rifle I've got. Unfortunately it does sit on the dovetail... mount a scope and it HAS to come off. But frankly this sight is so nice to use that one might be less inclined to go with a scope, especially considering the fact that this gun is not a high-powered, long-range rifle.

In any case - back to the shooting! Since this gun is moderately powered, I decided to test it for accuracy with 5-shot groups at my 10 yard indoor range using the factory peep sight. The first thing I discovered is that the gun is not crazy about Crosman Premier pellets - neither the domed in .177 or the hollow point in .22. Since I don't have a lot of different pellets, that put me back to testing Gamo's.

In .177, the rifle did about .5" groups with Gamo Match pellets. That might not sound like much, but this thing shoots these pellets better than any other rifle I've got (with the exception of my CFX). The groups tended to "cluster", with 3 or 4 shots virtually on top of each other, and 1 or 2 shots opening it up. I have no doubt that this gun would do even better with the right pellet. I did try Gamo Munters, but I was only able to shoot one group with them (I ran out!), and that group was slightly tighter than the Match pellet (around .4").

In .22 the rifle showed better results... and, oddly enough, it really seemed to prefer the very inexpensive Gamo Match pellet. It was able to put 5 of them into a .2" group, followed by a .35" group. That, I will point out, is absolutely the best I am able to do with open sights, even with the gun rested. The Gamo Hunter did slightly worse, on the order of .1-.2" more.

Side note - POI didn't change that much (at this range) when I switched barrels - maybe 1/2 inch or so. That's pretty good, and it gives me confidence that the barrel change mechanism isn't really hurting accuracy.

The overall feel and operation of the gun is a mixed bag. Cocking is still stiff, worse than many rifles with greater power. The rifle is also relatively large heavy for the power it puts out (about 7 1/4 lbs), although it is reasonably well balanced. The trigger is quite pleasant to use, and the sight - well, I've already said my piece on that. Cocking and locking the gun feels rough and clunky... a Gamo or even a Quest feels like a finely honed piece of machinery in comparison. On the other hand the firing cycle is only a little buzzy... my Gamo's (and the RWS 34 I had) were worse.

So, in the end... what's the verdict? Well, the rifle isn't quite the "master of all trades", which is what I think Mendoza was aiming for. It might be said that the gun is less than the sum of its parts... after all the trigger, the rear sight, the barrel swap mechanism and the "cocked" indicator are features that are nicely done. But the gun is severely hampered by what seems to be an inefficient powerplant - requiring a lot of muscle for very little result. The dual-caliber function itself works well enough, but I can't help but ask myself - what's the point? The answer that springs to mind is "hunting and target shooting", as the .22 barrel might be used for dispatching varmints and the .177 (with its cheaper ammo) for killing paper. But perhaps the gun seems a little weak for hunting, and the cocking feel and effort really detracts from the joy of target shooting or plinking. Then again, many airgunners have successfully used the B4-2 for small game at moderate ranges... and the RM2003 certainly has more power than that rifle.

I guess it comes down to this: If one wants the dual caliber... well, there's really no reason to stay away from the Mendoza. It isn't a bad gun, and it does have redeeming features... and it avoids that one bugaboo that will ruin a rifle faster than anything else - poor accuracy. Spare parts through Umarex do seem to be rather expensive, but I suspect that the Mendoza will rarely need them... I can't imagine that it will break that easily. As for me, I'm probably selling this one off, although I am tempted to keep it solely because for that rear sight! If it ever becomes available as an aftermarket part...

Offline PeakChick

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RE: Part 2 on the Mendoza RM2003....
« Reply #1 on: August 17, 2007, 01:11:16 PM »
Nice review Vince. It gives some good insights into the build quality and potential of the Mendozas as a whole.
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 Gene_SC

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Re: Part 2 on the Mendoza RM2003....
« Reply #2 on: August 17, 2007, 01:49:33 PM »
Again Vince another good review. Thanks again for giving us the lowdown on the Mendoza RM2003.

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 Big_Bill

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RE: Part 2 on the Mendoza RM2003....
« Reply #3 on: August 17, 2007, 06:02:32 PM »

Great Review Vince,

You had me hanging, and waiting for this your final post on the Mendoza RM2003.

Thanks for your time and effort in making this review !

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Always Use A Spring Compressor ! and Buy the GREAT GRT-III & CBR Triggers, cause they are GRRRREAT !

Offline Wade.S

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Re: Part 2 on the Mendoza RM2003....
« Reply #4 on: September 03, 2009, 10:44:34 AM »
Vince, that was a great review. I own a Mendoza RM 600 "not a duel cal rifle", mine is 22 cal. For the most part I agree with your review and enjoyed reading about your thoughts. FYI I have tried about 25-30 different pellets and have found the RWS super H point to shoot the best. If you have a chance to shoot them I would like to hear your thoughts on the accuracy.
2010 Air Rifle Kills
162 pigeons
280 starlings
49 various birds
100 ground squirrels
7 crows
24 rock chucks
1 pack rat
22 tree squirrels
1 rabbit