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Inside the Mrod CP-1M

April 14 2017 at 6:49 PM

cobalt  (Login cobalt327)
YF12

I received my CP-1M last week. First thing was to clean the barrel. It was fouled with a dark greasy deposit that looked a lot like moly grease. Not heavy but there, nonetheless. After cleaning the barrel and giving it a once-over, I shot it over the chronograph w/a fresh cartridge, 5 shots were made to equalize the cartridge before recording the MV:

10 SHOTS, CPHP 7.9gr 75°F
HIGH 481
LOW 457
AVG. 473 fps / 3.93 foot-pounds
ES 24
SD 6

The MV is maybe a little low compared to other guns w/o any power mods, but I’d say it was within manufacturing tolerances.

I used a few more shots to sight it in. After sighting it in, I used the rest of the cartridge plinking. The targets set up in my BY range from 10 to 30 yards. I didn’t shoot any targets for record but the accuracy seems pretty good.

For me the grips are awful. There’s plenty of wood there should I decide to rework them but hopefully someone will be making replacements, or possibly I can find one of the early grips to buy (Mrod doesn't have any). Also hoping a carbine stock will become available, like was mentioned when Mrod released their CP-1M.

Speaking of replacement/modification parts, I was hopeful this gun would catch on enough so that aftermarket parts would be made for it. But I’m thinking that if it hasn’t happened by now the chances aren’t very good. Now I'm wondering if anything will be coming down the pike from Mrod. I need to buy a couple spares of each O-ring to have on hand before I take the gun down again to do some modifications. I am going to email Mrod to order them, I’ll report back with the outcome.

So after shooting the first CO2 cartridge, I took grip back off and removed the trigger and sear for some attention. This is one very simple trigger. And it comes with a lot of gritty pretravel along w/a ton of overtravel. I adjusted the sear to get rid of as much pretravel as I could, while keeping the gun safe. BTW, I have seen where some people have adjusted the trigger set screw to have the set screw bear against the sear instead of the trigger cross pin. After trying it both ways, the photo below shows how I adjust the pretravel screw so it rides against the cross pin behind the trigger- not against the sear. Besides making the pretravel shorter, this also causes the trigger to move rearward in the trigger guard- which gives more room inside the too-small trigger guard.

[linked image]


The as-machined sear is rough from the wire EDM process (or whatever is used), and to a lesser extent the same for the contact area of the trigger. Both contact areas were smoothed using progressively finer wetordry paper on a piece of glass before polishing w/a felt buffing wheel and polishing compound. Then the factory sear spring was replaced w/a lighter one. Pull w/the lighter spring before polishing the sear and trigger was 20 ounces and notchy. After polishing the pull is 15 ounces and much smoother.

[linked image]


Then I turned to the trigger blade. The sharp edge is uncomfortable to me and needed smoothing. The trigger is flash plated; this will not be very durable. Just a FYI. I used a dremel sanding roll followed by a Cratex point then polished w/a felt buffing wheel and polishing compound.

[linked image]


Next I took the barrel off the receiver to see what things looked like. I’m glad I did because there was some fairly significant misalignment going on in the TP between the barrel and receiver:

[linked image]

The center set screw locates on a dimple drilled into the barrel that holds the barrel in position (the other set screws don’t have this- just the center one). There are several ways to go about correcting the misalignment but I decided to simply use a small piece of solder dropped into the center set screw hole. When the set screw is tightened the soft solder conforms to the off-center dimple and when all’s said and done the barrel is held securely in the correct position. This left the front sight tipped to the right so I recentered it.

So that’s it- for now. I still have more things to do and/or try. A few of them:
• Grip!
• Trigger over travel limiter
• Straighten trigger blade
• Deburr, detail and polish the hammer and polish sear hook
• RVA
• Open up trigger guard a little
• Polish leade if needed
• Carbine stock for occasional use

i'll post results as they become available.


    
This message has been edited by cobalt327 on Apr 17, 2017 9:18 PM


 
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robny
(Login robnewyork)
YF

nice work on

April 14 2017, 7:32 PM 

the trigger.. 15 ounces is awesome.. as for the grip , u may as well bust out the rasp file because the odds of an aftermarket grip set are slim.. The detachable stock would be a huge selling point on that model

 
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cobalt
(Login cobalt327)
YF12

Agree a carbine stock

April 14 2017, 8:20 PM 

should sell well. It was mentioned numerous times by Mrod in the early days but I haven't heard anything more about it in a long time now. I hope there's no problem getting the O-rings for it. Or at least the exact material, ID and cross section.

Rob, I seem to recall you having one of these? If so, did you rework your grip?

 
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robny
(Login robnewyork)
YF

I

April 14 2017, 9:53 PM 

do not have 1..Partly for the 2 reasons mentioned

 
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gubb33ps
(Login gubb33ps)
YF

Nice start...

April 14 2017, 9:19 PM 

I like those co2 pistols..look larger than they really are.

Part of the fun is finding out.


Adjusting the trigger as you have (screw OUT so it bears on the cross pin) does help a bit...keeps a little tension on the cross pins that hold the trigger parts in the housing, are a bit less likely to have a pin dribble out (but I'll still put a little square of tape over both sides...those little pins are hard to find when they do come loose).

Loading mags...another poster turned me on to this vid. It has no narration (it's not mine) and really doesn't need any. Not the way I started, but as soon a I tried it, realized how much easier this was.

https://www.youtube.com/watch?v=bfy9JSKve9I

Don't think they have the sales numbers here to expect much in the way of aftermarket goodies. Rectangular base of the wood stock is pretty much a uselss afectation. Human sized hands won't get any support from it, so it will eventually get reshaped. Good thing about a bit too large a stock: it's a whole lot easier to make a big one smaller than a small one bigger.

Know you were looking for the chekcered version of stock...haven't found those for sale...from what I can lear, were the same dimentions as the smooth version, so wouldn't really be any smaller.

Spares might be a problem if some major metal part breaks. Hasn't so far. As for o-rings, don't belive they use any that are unique, so replacements shouldnt be a real issue. The valve stem seal is unique (although shared with the co2 rifle and PCP rifle version), and if one of those needs replacing, think it's in the realm of home-made replacement.

Carbine stock could be done....it's a big wood grip, and reshaping it/splicing on a carbine type butt would be a lot easier than working with (partly hollow) plastic. Maybe I'll give that a try when (if) I get bored with it as a pistol.

As for changing the existing trigger...I'm not real sure what it's made out of, but doubt it will bend. The bolt and bolt handle are made from some mystery metal....it's not zinc, seems too heavy for the volume to be Al., it's not plated brass, but it's also non-magnetic. At least the trigger blade is magnetic, so I assume it's some form of steel, but I'd not really want to try heating/bending it.

Any way, hope you have as much fun with it as I have (and still am) having.

photo 6ae6cafd-a122-43a3-83c6-6526de1eead4.jpg

 
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Jason
(Login nervoustrigger)
YF12

Nice work!

April 15 2017, 8:55 AM 

I like your analysis of the trigger.

I got one a few weeks ago and it shoots great, even better after touching up the crown, and it's not pellet picky. With a red dot sight on top, it consistently drills the 1/2" spinners at 12 yards and the spoon spinners at 25 yards.

I was getting 48 shots inside of 8% on a cartridge, and yesterday I dropped in a couple of 50 durometer silicone O-rings between the hammer and valve and it went up to 84 shots without hardly any tradeoff in velocity. Much quieter now as well, of course. Details herehttp://www.gatewaytoairguns.org/GTA/index.php?topic=124266.0

Also, the O-ring sizes are listed there.

 
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cobalt
(Login cobalt327)
YF12

Thank you all...

April 15 2017, 12:00 PM 

Rob, gubb and Jason- thank you all for your contributions. I'm still very early in the learning curve of this pistol so the input is especially helpful to me.

@Rob, thought you had one, my mistake. Anyway, you are very experienced w/airguns in general so your input is appreciated.

@gubb36, the link on loading pellets in the mag will be a time saver. I fumbled around on the first few but got better after a while. But at first, I shot the two mags then resorted to the SS tray to avoid having to load the mags!
I may end up trying to fashion a carbine stock but not until I find a spare grip- I don't trust myself when it comes to woodworking. And I see now what you mean about the grip diameter, old vs. new. The old looks to be shorter but just as big OD.

@Jason- thanks for the tip on the hammer/valve O-rings. I'm all about good shot count, less ES w/o sacrificing too much MV, so that's perfect for me!

 
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