GTA
All Springer/NP/PCP Air Gun Discussion General => "Bob and Lloyds Workshop" => Topic started by: rsterne on November 27, 2016, 07:35:42 PM
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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....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/Front%20Both_zps7kweaqop.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/Front%20Both_zps7kweaqop.jpg.html)
Note the .25 cal Mag. is taller than the .22 cal....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/Side%20Both_zps0oadarsk.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/Side%20Both_zps0oadarsk.jpg.html)
Note that is it about 0.1" thicker, which is why it has more room inside for longer pellets....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/Back%20Both_zpsy34gx5bo.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/Back%20Both_zpsy34gx5bo.jpg.html)
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....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/All%20the%20Parts_zpsls0lwpqu.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/All%20the%20Parts_zpsls0lwpqu.jpg.html)
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....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/Parts%20Required_zpsslgtmuca.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/Parts%20Required_zpsslgtmuca.jpg.html)
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....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/Assembled%20Mag_zpsvzja1tqx.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/Assembled%20Mag_zpsvzja1tqx.jpg.html)
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....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/JSB%20Beasts%20Rear_zpsww5pbyut.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/JSB%20Beasts%20Rear_zpsww5pbyut.jpg.html)
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....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/JSB%20Beasts%20Front_zpsabkhvcbu.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/JSB%20Beasts%20Front_zpsabkhvcbu.jpg.html)
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....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/Hobbies%20Front_zpslkb3khrw.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/Hobbies%20Front_zpslkb3khrw.jpg.html)
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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Wow, you almost had it! :)
Someone use to sell a modified magazine for the .22 Marauder that had a circular relief milled out in the clear cover. It gave enough extra clearance to use the Polymags. I have one, and it works great.
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A .25 mag being WIDER is still not going to slide into a receiver with a gap set for the narrower .22 mag.
Or ... am i missing you widened out the receiver ?
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Bob, looks like all you would need to do is build up the pellet stop a little on the magazine housing to fix the over rotation issue.
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.
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Actually, the receiver is one of my own, but I want to be able to use .22 OR .25 cal....
Bob
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What I have not been able to find out is if the .177 and .22 bolts work in the .25 Breech... or if I have to mod a .25 bolt..?
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Bob, you can try to stick layers of insulating tape on a external house bump until pellet is line up.
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That might work, but there is another part of the problem I didn't mention.... The .22 cal wheel is a lot thinner than the .25 cal.... Remember I mentioned trying a spacer to move it forward in the magazine, but the brass pin is too short?.... The problem with the short pellets cocking in the hole is that the head is past the front of the thinner, .22 cal wheel, so only the skirt is inside the wheel.... The short pellet cocks in the hole, causing the problem you see in the photo of the RWS Hobby.... This leads to jamming of the wheel, and I have even had the second pellet pop out of the hole in the clear plate if you shake the magazine.... The only way to fix that issue is to either never use short pellets, or to make a new .22 cal wheel that is thicker so that the pellet can't go crooked inside the magazine.... I think this problem is made worse by the extra clearance between the OD of the wheel and the ID of the housing....
Could I add a bump/ramp to the inside of the housing and get it to work with the 34 gr. Beasts?.... Probably, but with the other problems remaining I thought it important to let everyone know that this conversion doesn't work as well, or as least isn't as simple, as I have been told.... Tape would be a temporary fix, just to see if the idea worked, but you would have to use something solid, and glued in place, as a permanent solution.... That is why I looked at the K&S tubing, but their sizes don't work, they are every 1/32" and we need one in between 1/4" OD and 9/32" OD to fit the notch and hole in the .25 cal housing and allow the bolt probe to pass through it on loading....
Bob
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Bob, Bob, Bob, this is so unlike you! Please pardon me chucking at your expense, because I know this is terribly frustrating and I feel your pain.
Crosman is all over the map on these magazines. I studied them quite a bit when I came up with the 30 cal mag.
(http://i226.photobucket.com/albums/dd79/loyd500/M-Rod%20magazine/30calMagAGL-sm_zpsc335ddaa.jpg) (http://s226.photobucket.com/user/loyd500/media/M-Rod%20magazine/30calMagAGL-sm_zpsc335ddaa.jpg.html)
The M-Rod .177 and .22 mags are the same outside dimensions (both fit a .437 O.D. barrel), and are about .589 thick.
The M-Rod .25 mag fits a .50 O.D. barrel and is about .680 thick. CL height of all 3 mags are the same at about .39".
The P-Rod .22 mag fits a .437 O.D. barrel and is .629 thk, oddly, thicker than the M-Rod .22 mag. CL height is .35". It holds 8 pellets instead of the M-Rods 10.
So basically nothing is interchangeable.
My suggestion for making the .22 cal pellets work in a .25 cal housing is a little involved, but will work.
First, the housing must be modified by building up the area around the ejection hole for the pellet with some 5 minute epoxy. Build up the area that the pellet and wheel stop against. Also build up a little bit of a ramp on the outer wall of the cavity right near the ejection hole so that the pellet will be guided into location over the CL of the ejection hole. After the epoxy is cured, set the housing up in a mill and center a 15/64 end mill over the original .263 hole that the .25 pellets ejected thru. Plunge the endmill thru the excess epoxy to make a .234 ejection hole for the .22 pellets. Then just take a 1/4" round file and hand work the adjacent areas to the correct contour. That should take care of the housing.
The .22 cal wheel that is too thin is a real problem. If nothing else, the spring will eventually pop out of the hole in the housing. The fix for the wheel is not easy, but will work. Epoxy two wheels back to back. The wheel is symmetrical, so back to back will work. After the epoxy is cured, mill the excess of the back housing off to make the remaining part the correct thickness. It will be difficult to keep the wheel from cracking while milling it to thickness. Taking the bulk of the material off on a belt sander will work if the wheel doesn't get over heated. Carefully deburr when done.
So with the those 2 mods, the mag should work well.
BTW, if you need some old .22 wheels, I have several "modified" .22 cal M-Rod magazines that someone had modified to fit a P-rod. They sanded the bottom of the mag off and used a shim in the P-Rod breech. A 10 shot mag instead of the usual 8 shot P-Rod mag. I think its a haggled up mod, but it worked for someone.
Lloyd
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What I have not been able to find out is if the .177 and .22 bolts work in the .25 Breech... or if I have to mod a .25 bolt..?
The answer is "yes" for most Gen II 25 cals. You have to watch out for the early Gen II 25 cals, they had a different breech, bolt, and lugs. If you go to the schematic, it calls out the serial number breakdown. I believe crosman did this to get the 25 cals out. It was released before the 177 and 22 cal.
A while back I built a 177 reg mrod, and started with a 25 cal breech and 177 bolt. The plan was to sleeve a standard crosman barrel, or if I went with a 0.640" LW barrel, it would have more "meat" in the breech. Unlike what Bob is trying to do, I just had to shim the back of the breech to get mag to fit tight. I had no feeding or bolt problems. Long story short, I had accuracy issues with my first sleeved 177 barrel, and went to another 177 barrel, unsleeved w/177 breech, and accuracy was good. I have not had an issue that would have me revisit with a 25 cal breech.
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I have several "modified" .22 cal M-Rod magazines that someone had modified to fit a P-rod. They sanded the bottom of the mag off and used a shim in the P-Rod breech. A 10 shot mag instead of the usual 8 shot P-Rod mag. I think its a haggled up mod, but it worked for someone.
I have done that. ;) Also, the 177 mrod mag can be modded the same and put in a prod w/mrod barrel.
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Oh, Lloyd, I was well aware that none of the mags were interchangeable.... so chuckle away, it was NO surprise to me.... My problem is that I believed the rumour that all you needed to do to convert a .25 cal mag to .22 cal was swap in the wheel.... THAT was my mistake.... ::)
Your solution is a good one, but a lot more work than I contemplated when I started this project.... of course that is nothing new, right.... Why am I surprised, is what I should be asking myself.... >:(
It's too bad that there isn't a size of K&S brass or aluminum tubing that is the correct ID (15/64) so that the .22 cal pellets and bolt probe would slide through.... Then I could use some 1/2 pieces of tube that were the right length to fit inside the 25 cal housing, and glue them into the 22 cal wheel, flush with the front edge to form cradles for the pellets, and make the wheel thicker at the same time.... I was prepared to purchase two mags (a .22 and a .25) to make one (wider .22).... but I kind of rankle at the idea of having to use three (two .22 cal wheels to make one mag).... I do appreciate your offer of a couple of spare .22 wheels, I may take you up on that if I can't figure out another way....
My other stumbling block for your method is that I don't have a 15/64" end mill, and none are available locally, it would be a special order.... I may have to figure out another method.... Using the very long 34 gr. Beasts I don't even need to make the wheel thicker, if I can get them to stop in the right place, which means I only have to mod the housing, if I stick to those pellets (or the 25 gr. Monsters).... The spring holds the wheel up against the clear faceplate, so I don't think there is any way it can pop out of either end....
I have two other alternatives.... I can glue shims on the bottom and back of PRod mags (which I have) to make them the same dimensions as an MRod .25 cal, and at the same time I could make them fit a 1/2" barrel.... Alternatively, I can machine the breech to fit the PRod mags, and should I decide to change to .25 cal, simply machine the mag slot deeper and wider, there is plenty of material, and I can make the bolt dimensions to suit each caliber, they need to be different nose diameters anyway.... I'm going to ponder this while I work on the breech for the next few days....
Bob
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Golly Bob! :( Then try this. ;)
Stick with the .25 and .22 M-Rod mags. Make the breech to fit the .25 mags.
Modify the .22 mags by opening up the barrel notch in the front to fit a .50 dia barrel if that is what your .22 is, or leave it at .437. whichever is appropriate.
Then just make a clever little clip-on shim that fits between the rear of the breech slot and the clear plastic cover of the mag. The clip on shim stays with the breech, not the mag.
Minimal modification. ;D Why won't that work?
Lloyd
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The 34 gr. pellets are too long for the .22 cal MRod mag.... but will fit in the PRod mag.... I MAY be able to machine the inside of the .22 MRod mag to fit the long pellets.... I could also glue a shim on the front of the .22 cal MRod mag (making it the same thickness outside as the .25 cal), giving enough thickness I could machine deeper, and I could even make it fit a 1/2" barrel stub.... That part doesn't really matter, as the .22 barrel could be 7/16" and the .25 cal barrel 1/2", or they could both be 1/2", of course....
PS I have used shims in breech notches before, that is indeed another solution....
Bob
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OK Bob, plenty of options. ;D It's in your court now. I am sure whatever you decide on will work great. ;)
Lloyd
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I found another interesting little wrinkle on this last night.... I tried the 34 gr. Beasts in my PRod mag and it won't rotate, they drag on the clear cover.... They are virtually the same length as the free length inside the mag.... Now I know that can easily be fixed with a Dremel, but I wanted to post that they won't quite work in stock form.... Interestingly, the original (long) Polymags will work perfectly in a PRod mag, and they are only a few thou shorter that the Beasts.... I assume it is the difference in nose shape as much as the overall length that creates the binding....
Machining the inside of the .22 cal MRod magazine deeper to fit the Beasts will break through into the recess where it fits on the end of the barrel, the plastic is quite thin there.... It's looking like gluing a shim on the back of the .22 cal mag, to make it the same thickness as the .25 cal, and then creating a new recess for the barrel, is the only practical way to convert a .22 cal MRod mag to work with the Beasts.... I may be back to modding the .25 cal mag instead.... ::)
Bob
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I think I'm zeroing in on a solution to this problem.... I have found that if you use the .22 cal wheel in the .25 cal body, and put a #011 O-ring on the shaft it rotates on, before you install the plastic cover plate, that takes up most of the play in the wheel.... In addition, by locating it forward (deeper into the housing), it holds all pellets much better aligned, and short ones can no longer tip sideways like the photo on the RWS Hobby at the bottom of the first post.... The only thing that is a problem with doing that is that the brass pin that rotates the wheel with the cover when you go to load the magazine is too short.... So, I will have to make a longer pin.... I'm pretty sure this solves the wheel problem, so that just leaves me modifying the housing to push the pellet that is in the loading position inwards and have it stop sooner, so that it lines up with the center of the barrel.... I'm not sure if I will do that with Epoxy, as Lloyd suggests, or make a plastic or metal half-tube and glue that in.... In any case, I now plan to make the breech for my Disco Double to fit the .25 cal magazine.... and somehow get one (or two) to work with .22 cal pellets.... That will allow conversion to a .25 cal (or even a .30 cal) later if desired....
Bob
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I spent all afternoon and evening reworking the two .25 cal housings to accept the .22 cal wheels.... The solution I wrote about above, spacing the wheels down with an O-ring and making a longer brass pin to rotate the wheel with the cover for loading, worked perfectly.... As Lloyd suggested, I built up the inside of the .25 cal housing in the vicinity of the through hole so that the pellets stop in the right place to line up with the barrel.... Instead of using Epoxy, which doesn't "machine" very well, I used a medium viscosity Cyanoacrylate glue called "ZAP-A-GAP" which I used to use extensively in my R/C Modelling.... It is basically a "Crazy Glue" but thicker, and there is a spray hardener for it that sets it instantly, so you can build it up a layer at a time in pretty much any shape.... It cures to form an clear, hard Acrylic plastic, basically plexi-glass.... Like any crazy-glue, it sticks to almost anything, and it bonds so well to the plastic of the housings you can machine it and grind it, and you can't tell when you grind through the glue and hit the plastic.... Effectively, it becomes one solid piece.... I built up the inside of the through hole, and the adjacent part of the housing, also building a ramp to push the pellets towards the wheel....
I didn't have a 15/64" mill to machine out the hole and pocket, but I did have a 7/32", and after carefully centering the magazine housing off the original through hole I shimmed one side of the mill in my 3-jaw chuck a few thou to make it run off center and cut a 0.234" hole.... This is the same size as the .22 cal magazine, so when used with the .22 cal wheel, the pellets stop perfectly aligned with the barrel.... Most of the time was spent with a Dremel with various burrs, and a set of "rifflers" (small hand files) to make the ramp a smooth transition so that the pellet fed smoothly over to where they stopped in the milled hole.... There were the inevitable unintended fillets in all the corners from the glue that had to be removed so that the wheel rotated smoothly without hanging up.... It amazes me how long this kind of thing takes to do.... I spent well over 2 hours per magazine before I was happy with the results.... They now feed any .22 cal pellet I tried perfectly, so it was worth it.... However, for a project that was supposed to be a simple "drop in the .22 cal wheel", this turned into a nightmare to accomplish....
The results, however, are that I have a pair of .22 cal MRod magazines that are 100% interchangeable with my .25 and .30 cal mags.... and that will allow me to use any of the three on my new Regulated Disco Double.... 8)
Bob
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Nice work and great read, Bob. Can you post pics of your end results?
Joe
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Here are pics of the finished mags, Joe....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/Finished%20Mags_zps9x9nd2ae.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/Finished%20Mags_zps9x9nd2ae.jpg.html)
You can see the #011 O-ring through the clear cover, it partly obscures the numbers on the wheel.... In the back view, if you look carefully you can see a ring of clear plastic around the head of the pellet, where the hardened glue made the through hole smaller.... Note how perfectly the pellet is centered in the bore now....
Bob
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Bob,
I knew you would come up with a great solution, and you did, even if it is time consuming. That zap-a-gap crazy glue sounds pretty cool, I will have to try and find some to add to the "adhesive collection."
So, you ended up using the size 011 o-ring as a spacer for the wheel/spider? If that seems to be creating too much drag, one of the hard PTFE o-rings would be pretty slippery.
Lloyd
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A size #010 would fit over the shaft but drag on it, so I chose the #011 as it is only a spacer.... There is still some free play vertically in the wheel, the only thing pressing the wheel up against the O-ring is the torsion spring inside the mag, which has almost no end force.... Friction doesn't seem to be an issue, once I got the proper clearance between the ends of the "teeth" in the wheel and the bump in the magazine that stops the pellets (I built it up too much and had to grind it down again).... but if I ever experience any sticking when the mag is down to 1 or 2 pellets (when the spring tension is the weakest), I will try your suggestion....
I couldn't function in my shop without a supply of ZAP and ZAP-A-GAP and the spray "ZIP-KICKER" (I hardly ever buy the thick one).... The thinner ZAP is a wicking type CA glue, you assemble the parts and put a tiny drop of glue on the edge and "ZAP" they are forever bonded together.... Both glues come with two applicators to control the amount of glue.... One is a piece of tiny poly tubing, with a bore of about 0.015" to deliver TINY drops of glue.... You don't need much !
Bob
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I see no reason that the same solution would not apply to fitting a .177 wheel inside a .25 cal MRod magazine body.... That would allow the use of the 24 gr. NOE .172 cal bullet in a .25 cal MRod receiver fitted with the TJ's 9" twist .172 cal barrel....
http://noebulletmolds.com/NV/product_info.php?cPath=102_576&products_id=5456 (http://noebulletmolds.com/NV/product_info.php?cPath=102_576&products_id=5456)
The 26 gr. NOE bullet is just a bit too long, however, at 0.493"....
Bob