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PostPosted: Sun Nov 27, 2016 6:34 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8976
Location: Coalmont BC
If like me you have heard about doing this to allow for longer pellets or bullets, but hadn't tried it before, you may be VERY interested in the results I got.... First of all, here are three views of the stock Crosman mags.... .25 cal on the left, .22 cal on the right....

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Note the .25 cal Mag. is taller than the .22 cal....

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Note that is it about 0.1" thicker, which is why it has more room inside for longer pellets....

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Also note that the boss that slides onto the end of the barrel is 1/2" on the .25 cal mag, but only 7/16" on the .22 cal, because that is the diameter of the barrels on the respective MRods.... You will notice that the hole to feed the pellet on the .25 cal is larger as well, which makes sense.... However, as carefully as I can measure, the distance from the center of the barrel to the bottom of the mag. is the same on both....

OK, so right off the bat, you can't put the .25 cal mag in a .22 cal MRod, so why bother?.... Well, if you want to build a .22 cal, or a .224 cal, on a .25 cal action, then maybe this can be made to work, and you can use longer pellets or bullets than will fit in the stock .22 cal mag.... The idea is to use the 10-shot wheel out of the .22 cal mag. and install it in the .25 cal housing.... So, when you take both mags apart, here is what you have....

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The .25 cal housing is not only larger on the OD, but on the ID as well, and the same goes for the wheel that holds the pellets.... and of course it only holds 8 pellets instead of 10, and it's a LOT thicker.... The springs and screws are identical, and the cover plates are the same thickness, and the pins are in the same place, but they are slightly different in OD.... So let's select the parts we need, as below....

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We want the .25 cal housing, but the cover plate and wheel from the .22 cal, one spring and one screw.... Put them all together, and you get this....

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The .22 cal wheel is a lot thinner than the .25 cal, but the spring holds it up against the cover plate, so the brass pin still engages the slot properly to prevent the cover from going all the way around, so that part works.... I tried using a spacer between the wheel and cover to take up the extra room, but that moves the wheel down and it doesn't engage the pin, so you have to just allow the spring to push it up into place, which it seems to do fine.... Loading is as per normal, but once loaded is when I began to notice the problems.... My purpose was to allow me to use the new .22 cal 34 gr. JSB Beasts in my new Regulated Disco Double build, so I loaded them up first....

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At first glance it looks great, but when you look closely, you will start to notice some problems.... Since the OD of the .25 cal mag is larger, the pellets can move radially and you will notice a gap on the inside or outside of them.... When they get to the bottom hole, in line with the barrel, they are forced inwards by the taper on the outer housing, and sit tight against the wheel.... but if you look closely, you will notice that the wheel can over-rotate slightly, and the edge of the skirt is actually past the bottom edge of the hole in the clear plate.... so the bolt probe will not hit the center of the pellet.... In fact, the full diameter probe I plan on using with my retractable bolt might even hang up on the web of the wheel between pellets.... When you turn it over....

Image

you see the exact same thing.... The nose of the pellet is not lined up exactly with the center of the barrel.... Now with a round nosed pellet, this might not be a problem.... but look what happens with an RWS Hobby wadcutter....

Image

The combination of a short pellet and the over-rotation of the .22 cal wheel in the larger .25 cal housing actually causes the pellet to tilt sideways.... and I mean a LOT.... Note that the skirt is being forced downward by the wheel, which actually tilts the nose of the pellet upwards to the point it catches on the hole.... and remember that the .22 cal barrel is even smaller than the hole in the .25 cal housing....

I tried a bunch of different pellets, and realistically the only ones that fed without hanging up or other problems were the original (long) Predator Polymags, JSB Monsters and JSB Beasts.... Baracudas, JSB Heavies (or shorter) and virtually any of the shorter pellets I tried would double load (a second would fall through the hole when I pulled the pin punch I was using as a probe back), or the pellets tilting in the mag would cause it to bind.... Remember, I wasn't trying to get this to function with a barrel in place, either, I was just poking the pellets out with a pin punch acting like a conventional bolt probe to check if the mag functioned.... I also never tried a full diameter bolt probe either, like the retractable one I will be using in my DD....

So what are my conclusions about this mod, which I have heard about numerous times?.... Well, first of all, I wouldn't even try to use it if the pellet you want to use will fit in the original .22 cal mag.... It's designed for the job and works great.... So that leaves the question if this is a suitable option if you need to have a magazine to feed longer pellets or bullets than will fit in the stock .22 cal mag.... Will making a .22 cal mag in a .25 cal housing work in that case?.... I have heard it does, but from what I see here, looking at it closely, I would have to say it's a big MAYBE.... If people find it's working for them, it may well be because the combination of a long pellet/bullet and the nose shape allows smooth loading, even though the alignment is poor....

It might be possible to shim out the .25 cal mag body in the vicinity of the last pellet position where it is supposed to stop in line with the barrel.... I looked at the possibility of using some K&S hobby tubing, and there isn't a size that will work without modification.... It might be possible to make shims for each notch in the .25 cal wheel to hold the .22 cal pellets properly.... or it might be possible to 3D print a new .22 cal wheel to fit the .25 cal housing, but I don't know how any of those solutions would get the pellet/bullet to stop lined up perfectly with the barrel.... because it is the edge of the pellet hitting the outer housing that governs the alignment with the hole in the back, and hence the barrel.... I think only modifying the outer housing would do that.... It might be as simple as a drop of thick crazy glue and some spray hardener (which basically makes a lump of plastic, stuck to the housing) and then file it down by hand until the pellet stops lined up.... However, I can't recommend just swapping the .22 cal wheel into the .25 cal housing, which is what I have heard you could do.... I will, unfortunately, have to look for another solution to allow me the option of using either .22 or .25 cal barrels interchangeably in my new Disco Double....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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