Author Topic: First Tuning...Questions...Mendoza Rm 600  (Read 9496 times)

Offline toddk63

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First Tuning...Questions...Mendoza Rm 600
« on: April 02, 2010, 07:19:17 PM »
Mendoza RM 600 .177 that I have had for about a year now, maybe 1000 to 1500 rounds shot through it.  Just chronied Beeman CrowMags 8.8 gr. at 760 fps after cleaning the barrel. Decided to take apart and tune it.  Built the spring compressor today.  Disassembled tonight. Some things I noticed and have questions about.

The piston is VERY tight.  It can not be moved easily by hand.  Requires some tapping with hammer and dowel to get it all the way in and pushing on the slot with a screwdriver to get it out.  Is this normal?  I read one tuning pamphlet that mentioned looking for tight spots, but what to do about these tight spots?  Charlies "B19 Super Tuning" guide mentions a new seal may be that tight, so maybe I am worrying about nothing.

The compression chamber walls appear to be mirror finished.  If it is already this finely polished, should I bother honing it?

Finally, I have Moly paste but no heavy tar. In a pinch, could I use the moly paste on the outside of the spring in place of the heavy tar?

I plan on using Charlies "B19 Super Tuning" guide as my example of where to polish and where to lube.

Thanks,

Todd K.

Offline tjk

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Re: First Tuning...Questions...Mendoza Rm 600
« Reply #1 on: April 03, 2010, 02:39:21 AM »
Hey Todd, if you don't have any tar on hand, you might try a sticky type grease like 5th wheel grease. Not the best, but it's worked for me in the past, and I'd save the moly for other uses. Your numbers sound a little low for the rm. How does the seal look? I'd like to see some pix of the rifle broken down. Have you measured the spring to see if Macarri has one that will work? Your spring may be 'spent'. About the seal size, it all depends, but if you clean it up and moly the piston around the seal and rear end of it,  you will never need to "oil" the rifle which maybe why the piston is hard to get out of the action. JMO, oil is a poor type of lubricant for spring guns,...grease and moly is much better.  Hope this was some help, tjk
PS post some pix!!
397 Benji-98\' model    
Marksman  0035, My Fav!,CDT T\'d
Crosman Sierra-Pro,.177
Benji 392 08\'
CDT TT\'d RWS 34 .22,CP 4-16X40 AO
MM T\'d Marksman 0035
Crosman G1 Extreme
Daisy PowerLine 1000
TF-97 .22
B-28A MM T\'d
B-28 OEM Tuned by me
Beeman .22 RX-2 w/Theoben GR
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Offline toddk63

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Re: First Tuning...Questions...Mendoza Rm 600
« Reply #2 on: April 03, 2010, 03:00:59 AM »
Thanks tjk.  I'll work on getting some pics up. The seal (synthetic) looked fine.  Of course, it is the first one I have ever seen...The spring looked OK as well. It looks like they actually took the time to polish the ends of the spring at the factory. I think this gun has always had these low velocities, when not dieseling.  Rumor has it, the Mendozas derive their stated velocities with a little extra combustion. The piston is a little rough and could use some polishing.  If I had to guess, the tight piston seal is eating up considerable spring power resulting in the low velocities.

Now to clarify something you said.  Are you suggesting to use moly paste on the piston seal and in the compression chamber as opposed to the less detonating silicone oil?

Thanks,

Todd K.

Offline tjk

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Re: First Tuning...Questions...Mendoza Rm 600
« Reply #3 on: April 03, 2010, 04:13:00 AM »
Yes! That's exactly what I mean. With the piston seal and sides of the piston body lubed with moly, the whole action will cycle much smoother as a whole than with using silicone oil that will eventually 'dry out' from use. As a result, I have a good hunch your FPS's will increase a good bit more. Yes Mendoza uses the dieseling/detonation phase to get its velocity #'s, but I'm sure the moly will work much better in the long run!! tjk
397 Benji-98\' model    
Marksman  0035, My Fav!,CDT T\'d
Crosman Sierra-Pro,.177
Benji 392 08\'
CDT TT\'d RWS 34 .22,CP 4-16X40 AO
MM T\'d Marksman 0035
Crosman G1 Extreme
Daisy PowerLine 1000
TF-97 .22
B-28A MM T\'d
B-28 OEM Tuned by me
Beeman .22 RX-2 w/Theoben GR
Beeman .177 R1 Santa Rosa

Offline toddk63

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RE: First Tuning...Questions...Mendoza Rm 600
« Reply #4 on: April 03, 2010, 07:16:42 AM »

Offline toddk63

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RE: First Tuning...Questions...Mendoza Rm 600
« Reply #5 on: April 04, 2010, 02:39:51 AM »
OK, my first tuning job is done.  Cleaned, polished, lubed.  Re-assembled, after battling with that dang trigger problem.  Just chronied it post tuning...760 fps with Beeman CrowMag 8.8gr....Exactly the same as before!  It does seem to shoot a bit smoother though.  The piston was still almost as tight on re-assembly.  I may try a new seal in a couple of weeks.

So the only thing I gained is some in depth knowlegdge on the dis-assembly and re-assembly of a Mendoza RM 600.

Thanks,

Todd K.

Offline toddk63

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RE: First Tuning...Questions...Mendoza Rm 600
« Reply #6 on: April 05, 2010, 05:16:59 PM »
I was kind of light handed with silicone di-electric grease on the piston seal when I re-assembled, none inside the chamber...just on the seal.  I know tjk said lube the seal with moly but I was going by the B19 Super Tune doc.  Then I found this:

http://www.pyramydair.com/blog/2006/08/spring-gun-tune-part-13-range-testing.html

The pictures showed me just how much moly to put on the seal and said to lightly lube the chamber as well.  So here it was 10:45 PM on a work night and I launch in to tearing down that rifle...again.  A little experience goes a long way.  I had the seal out, lubed it and the chamber and reassembled in a little over a half hour.  Then chronied a few shots with .177 Crow Mag 8.8 gr.  The first couple were loud and smokey around 970 fps!  It then settled in around 770 fps...I gained 10 fps!!!

Todd K.

Offline tjk

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Re: First Tuning...Questions...Mendoza Rm 600
« Reply #7 on: April 05, 2010, 11:15:14 PM »
Just Keep shooting the rifle and see if your #'s don't start to climb some! Congrads on your first tune!!! tjk
397 Benji-98\' model    
Marksman  0035, My Fav!,CDT T\'d
Crosman Sierra-Pro,.177
Benji 392 08\'
CDT TT\'d RWS 34 .22,CP 4-16X40 AO
MM T\'d Marksman 0035
Crosman G1 Extreme
Daisy PowerLine 1000
TF-97 .22
B-28A MM T\'d
B-28 OEM Tuned by me
Beeman .22 RX-2 w/Theoben GR
Beeman .177 R1 Santa Rosa