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Mrod CP-1M, problem chambering pellets

April 18 2017 at 8:00 PM

cobalt  (Login cobalt327)
YF12

My Mrod CP-1M chambers pellets rather hard (worst so far being Winchester 9.8 gr round nose, plinking ammo). But all types/brands of pellets that I have chamber harder than what I’m used to. The bolt works smooth if no pellet is chambered. The rear of these Winnie pellets also tip upwards just as the head hits the 90 degree edge or lip. Pushing the pellet in by fingertip helps some w/the tipping but it’s no easier to chamber.

The pellet on the left side in each photo (same pellet in each view) was chambered then carefully pushed back out the breech. Pellet on right is an unchambered pellet of the same type.

[linked image]


Below is the lip I’m referring to:

[linked image]

My questions are:
1. Does the edge need to be smoothed so there’s a softer transition than the 90 degree lip?
2. Is there a diagram or blueprint of a .177 pellet gun chamber/leade available?



    
This message has been edited by cobalt327 on Apr 18, 2017 8:02 PM


 
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robny
(Login robnewyork)
YF

looks like

April 18 2017, 8:50 PM 

u need to pull the barrel off and chamfer the rear of it.. A slight taper with a dremel tool like you were doing a crown , then reinstall and test again.. repeat till u get the desired result.. the lowest angle possible is ideal, 60 degrees or below and shallow


    
This message has been edited by robnewyork on Apr 18, 2017 8:52 PM


 
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cobalt
(Login cobalt327)
YF12

Re: looks like

April 18 2017, 9:58 PM 

Sounds like a plan. I 'preciate it.

 
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Jason
(Login nervoustrigger)
YF12

Just bevel the edge

April 18 2017, 8:58 PM 

If I'm interpreting your photographic markup correctly, it appears the barrel leade is not concentric with the opening in the breech, and there is a lip that is causing the pellets to hang up. I would simply apply a slight bevel to that area, or perhaps to the full perimeter in case there is a spot at the top you can't see.

But before doing that, I suggest evaluating the barrel by itself. That is, push a few pellets through to see if the leade has any issues that are causing the rough chambering. Most barrels will benefit from polishing the leade and breaking the sharp edge where the rifling begins.

 
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cobalt
(Login cobalt327)
YF12

Re: Just bevel the edge

April 18 2017, 9:57 PM 

The leade may not be concentric any longer (if it ever was) because of me rotating the barrel to correct a misaligned TP.

[linked image]

This shouldn't have caused a problem, but who knows. I'll tear this back down tomorrow to see what it all looks like, and to try to figure out why I'm getting light piercings on the cartos.


    
This message has been edited by cobalt327 on Apr 18, 2017 10:14 PM


 
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Jason
(Login nervoustrigger)
YF12

Piercing CO2 cartridges

April 18 2017, 11:22 PM 

I didn't realize at first this gun does not pierce the cartridge by way of firing. You simply tighten the end cap until you hear it open and pressurize the valve.

What's interesting is, firing does somehow produce enough disturbance to pierce it. Just not very well. I know because I did it that way for the first 5 cartridges.

 
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cobalt
(Login cobalt327)
YF12

Who knew? haha

April 19 2017, 10:54 AM 

Thanks Jason, I'll be sure to tighten the cap until I hear gas next time. And like you mentioned, I was able to pierce the first cartridge more or less normally by 'dry firing' it but I probably had the cap tighter than I did the 2nd. one.

 
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