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Slavia · Moderator

I picked up this Crosman (Mendoza of Mexico) RM577 a few years ago - on clearance, of course. I think it was about $80.00 USD in the "Bargain Cave" at Cabela's. I tinkered with it a bit, but it never really inspired me. 2009 is the time to fix that.

I think this one will be for offhand shooting at 25m-50m outdoors. The firing cycle is fairly smooth (no twang), but the trigger is horrible. It's fun to use aperture sights for variety, so I'll keep those. Cocking is really rough, and mechanical fit/finish is worse than Chinese. Velocity with RWS Superdomes is Mean=790 FPS (Min.=77, Max.=805, S.D.=9.61, n=10). Accuracy for a 10m group was Max. Dispersion=0.87," Mean Radius=0.40," n=5.

Here's the vibration pattern. It doesn't mean anything, except for comparing before and after. This one has spikes out to 50 dB (my factory G1 spiked to 100 dB):

I'll try to keep velocity about the same, but smoother if possible. This time around I think I'd like to try brazed piston buttons just for fun.

I also want to make a stock, just to say I did it. It won't be adjustable, since I can fit it to my needs from the beginning. With a little chunkier forearm, I can probably squeeze in a short accessory rail. This is the Tyrolean design that Broommaster and I were discussing in an earlier thread:

The trigger is a non-adjustable single stage design. The trigger blade acts directly against the sear. Besides smoothing it out, I'd like to devise some kind of additional spring to give it the "feel" of a two-stage trigger. I already added a decent trigger shoe.

I had already played with the sights a little. It came with a fiberoptic front bead, which I changed. I also "thickened" the front sight hood so I could see it better, and added a spirit level. Those will need to be refined. I would also like to extend the sight radius by moving the front sight forward on a new muzzle brake, and the rear sight back.

So stay tuned. For any RM series owners following this, here's the schematic (the RMx77 series guns were the same gun with different springs):

broommaster2000 · Moderator

Aw, you shouldn't have... Thumb Up!

Another one of those projects. You never stop do you? Mr. Green

cw · Banned

What software did you use to acqire the sonic graph?

Slavia · Moderator

I used the sound recorder and volume control (microphone on full) that comes with Windows. I just put the microphone up against the compression tube and pulled the trigger. Then I saved it as a .wav file.

The waveform program is called "Nero Wave Editor." It is part of a suite called "Ahead Nero" that came bundled with my CD burner.

cw · Banned

Thank you, Sir. I'm running Windows and have Nero, so I'll
give it a shot (pun intended).

I wonder what the wave for the Condor will look like.

Slavia · Moderator

It goes without saying (but I'll say it anyway): Be sure the gun is pointed in a safe direction when you're fumbling with the microphone.

I start the recorder, pull the trigger, and then stop the recorder. This gives a lot of nothing, with one small "event" in the middle. I use the wave editor to crop the .wav file down to just the event.

Since I'm taking a before/after "snapshot," I make sure the microphone gain settings are the same both times. There is a vertical scale zoom in the Nero software that lets you expand or contract the graph to see detail (with dB markings on the left side). I also convert the graph from stereo to mono using the software. Then, I just use the Prt Scrn key to capture an image of the screen, and then crop out the junk with a graphics editor.

cw · Banned

Safe direction? Why on earth would I want to do that?

dummyracer36 · Senior Member

with that condor... is there really any safe direction?? Faq-U

cw · Banned

According to chairegun it will only go a little over 740 yards (0.42 miles)
on high power with a 28.4 grain Eun Jin dome. At 100 yards the
projectile will still have 21 fpe left. Drop from muzzle is 5 inches at
100 yards.

That's what makes airguns so attractive for pest control. With their
inherent accuracy and the projectiles having a narrow waist and deeply
hollow base, they are putting the brakes on the moment they leave
the muzzle.

cw · Banned

Slavia, thanks for yet another exploded. would you happen
to have the parts list for it?

That RM's trigger looks to be quite primitive.

Roy · Veteran Member

Slavia,

Pack some of them shootin' irons when you come for the Holiday get-together. I would love to see your more recent projects "in person".

I'll bring the Morgan adjustable buttplate so you can decide if you want it.

cw · Banned

Morgans are nice. Is it a plastic one, or one of the old
aluminum ones?

Slavia · Moderator

Roy · Veteran Member

CW,

The Morgan buttplate is all aluminum, except for the rubber of course.
I just don't need it. Maybe Slavia can incorporate it into his next project.

Slavia · Moderator

An adjustable butt or comb on a Tyrolean stock is going to look goofy, so my plan is to make the stock to my own measurements from the start. That means getting the rear sight position squared away - my intention was to extend the sight radius. Moving it backward also implies moving it upward to clear the safety lever.

I had a Gamo adjustable-elevation scope base that fell apart on my G1; I used the bottom (clamping) half for this project. I also had a piece of dovetail rail from the junk room at a local gun store. The knobs came from Radio Shack. Everything else came from Walmart or Charlie's Hardware (the only hardware store in town).

Small scratches on the sight proper were touched up with automotive touch-up lacquer. The clamping base, rail, and part of the sight were repainted with self-etching primer and black barbeque paint. Everything was baked at 350 Deg. F. for 20 minutes, and treated with Armor All when cool.

All the turning was done with a portable electric drill and a Dremel, using screws as mandrels when necessary.

The net result is a position translation of 1.050" to the rear and 0.850" upwards.

More information about the sight that came with this gun:
http://www.airgunwarehouseinc.com/py-a-2003.html