Mendoza RM-2800 .22 cal. repeater - Part 2
by B.B. Pelletier
Following the advice of some readers who noticed a similarity between the Mendoza RM-2800 and the RM-2000 I tested for you back in May and June of last year, I tested this rifle with most of the same pellets. We can expect the barrels to be the same on both rifles, but the advertised velocity of 950 f.p.s. leads me to believe the 2800 will be faster than the RM-2000. So, I 'll report velocities of pellets for both guns.
One thing I forgot to do until late in the RM-2000 test was clean the bore, so that was the first order of business for this rifle. The procedure is 20 strokes through the bore in each direction with a new brass brush loaded with J-B Non-Embedding Bore Cleaning Compound, and then cleaning patches until they come out clean. The bore was not too dirty on this rifle, so it cleaned up fast. Now, on to velocity testing.
I chose these because the RM-2000 was most accurate with them. I never chronographed them, though. In this rifle, they varied from a low of 411 f.p.s. to a high of 702. While a variation like that would normally be attributed to dieseling, I don't think it is in this case. Even at 702, the velocity is too low for this rifle. I think it leaks air at the breech seal. Testing with other pellets helped confirm that.
Crosman Premiers were next. They ranged from a low of 291 f.p.s. to a high of 608. They do feed through the magazine, and the slowest ones were those fed from the mag.
I tried RWS Super-H-Points next. They went, 393, 398 and 400, respectively. I did not finish a string with them.
RWS Hobby pellets were the last ones I tried. They went 381, 405 and 397 f.p.s. That concluded the test of this rifle. Please note that the few higher velocities I recorded came with the first two pellet tested.
So much for my grand plans!
These velocities are unacceptable. They don't represent what this gun is capable of, so something is clearly wrong. There aren't many easy fixes for a breakbarrel when this happens. In fact, the best one that comes to mind is Vince's shimming of the breech seal that will be reported later this week. That may be even more important in this case because of Mendoza's sliding pellet carrier, which needs a seal on EACH SIDE of the moving carrier. That's two chances to leak air, which is what's happening...I think.
If this were an easy fix - something anyone could do - I would do it and report the results. Because of the requirement to disassemble the repeating mechanism to fix the interior breech seal, I'm going to pass. I can probably do the work without much problem, but most airgunners don't have my experience or my tools.
If you look back at the test of the RM-2000, you'll see the pellet velocity was much tighter than with this rifle. I think the seals on the pellet feed mechanism are not doing their job.
So, the test of this RM-2800 is over. I have an Air Venturi Avenger 1100 on order. That's a Mendoza breakbarrel without the repeating mechanism. I'll test that for you when I receive it.
I'm sorry things turned out this way. I'm going to return this rifle to Pyramyd Air.