Mrod CP-1M, problem chambering pellets

Mrod CP-1M, problem chambering pellets

Joined: June 9th, 2016, 11:17 pm

April 19th, 2017, 12:00 am #1

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.




Below is the lip I’m referring to:



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?

Last edited by cobalt327 on April 19th, 2017, 12:02 am, edited 1 time in total.
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Joined: April 28th, 2010, 12:23 am

April 19th, 2017, 12:50 am #2

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
Last edited by robnewyork on April 19th, 2017, 12:52 am, edited 1 time in total.
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Joined: June 4th, 2013, 4:42 am

April 19th, 2017, 12:58 am #3

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.




Below is the lip I’m referring to:



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?
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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Joined: June 9th, 2016, 11:17 pm

April 19th, 2017, 1:57 am #4

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



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.
Last edited by cobalt327 on April 19th, 2017, 2:14 am, edited 1 time in total.
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Joined: June 9th, 2016, 11:17 pm

April 19th, 2017, 1:58 am #5

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
Sounds like a plan. I 'preciate it.
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Joined: June 4th, 2013, 4:42 am

April 19th, 2017, 3:22 am #6

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



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.
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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Joined: June 9th, 2016, 11:17 pm

April 19th, 2017, 2:54 pm #7

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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