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 Post subject: Re: Tale of Two BRods
PostPosted: Wed Mar 21, 2018 9:01 pm 
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Location: Coalmont BC
Well I got sidetracked on the long .357 aluminum mag project.... I had another look at the .25 cal MRod mag. and came up with a different way to modify it for .35 cal and still use the original housing, albeit modified somewhat.... The first step was to make a .35 cal wheel that would fit inside the .25 cal mag. and the only way to do that was to reduce the radius that the holes are on that hold the pellets from 0.50" to 0.45".... This would normally raise the center of the pellet 0.050" above the boreline, but I realized that if I inserted the magazine further to the left, while keeping the feed hole at the same height (which it must be to align the pellet with the bore), I could just rotate the wheel a bit more counter-clockwise (when viewed from the back) to get the height to work out.... here are some photos of the work so far....

Image

The wheel was machined from a piece of MDS, with seven positions, one of which uses a glued in blanking plug that prevents you from closing the bolt when the mag. is in the empty position.... Drilling 7 holes was a challenge with a manual milling setup, the key was to use an online calculator to convert from Polar coordinates (radius and angle) to Cartesian (x and y) coordinates, and then just position the vertical and crossfeeds on the milling attachment on my lathe to drill the 7 holes around the 0.9" diameter circle.... It worked out great, although there was a lot of hand finishing to do, removing the milling flash where the holes broke through the outer diameter of the wheel.... You will notice that the recess in the back of the wheel for the torsion spring is smaller in diameter, so I will need to find or make a smaller OD spring to force the necessary rotation of the wheel to make the mag. self-index....

Image

Here is a photo with the wheel in place, but I have not yet moved the feed hole over in the outer casing, or milled away part of the bump stop to make it stop in the correct place.... In the photo below I have machined a larger hole in the clear cover in the correct location.... You can see that it is shifted about 0.090" to the right of the original location.... and you will notice that part of the bump stop will have to be machined away when I mill the hole in the outer housing in the correct location to allow the mag. to slide to the left....

Image

There are lots of things that will remain to be done to make the mag. functional.... the spring as I mentioned, and a new location for the small brass pin that rotates the wheel to allow loading pellets when you rotate the cover.... I will also have to figure out a way to hold the mag. in place, because the slot in the front for the barrel will lose the little bumps that allow the mag. to "snap" into place on the barrel stub.... First I have to get the mag. to function and line up.... then I will worry about the details....

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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 Post subject: Re: Tale of Two BRods
PostPosted: Thu Mar 22, 2018 5:52 pm 
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Location: Coalmont BC
I took me many hours and lots of hand work, but I now have a fully functional 6-shot .35 cal MRod magazine, made from a .25 cal.... Here are the photos....

Image

The spring is a mess, cosmetically, but it works.... I made it by winding the stock spring around a 9/32" drill bit to tighten the coil enough to fit inside the 1/2" hole in the wheel.... Of course it came out a mess, so I spent a lot of time with two needle-nose pliers tweaking it to get it to work.... ::) .... I had to hand carve the groove for the pin in the cover that rotates the wheel with a tiny burr on a Dremel, and again it may not be pretty but it is functional....

Image

The housing was milled out with a 3/8" end mill to move the hole over and increase it in size.... There is a 1/32" hole drilled through the filler plug in the wheel for the tail of the spring, which is installed in the photo....

Image

The position of the feed hole, and it's associated recess that clips over the end of the barrel were the key to this project.... They are the same height as in the stock .25 cal magazine, but are moved 0.084" towards the centerline of the mag..... That was necessary for the hole to line up with the smaller radius of the wheel, which was necessary so that the pellets fit inside the housing.... I was concerned about how to retain the magazine in the slot, but as it turns out, that was a non-issue.... When I plunged the 1/2" mill into the front of the housing to create the recess, it left two tiny bumps that slide past the barrel when you insert it, exactly the same as on a stock mag.... The difference is that as you slide the mag. into place, you feel it "click" twice as it slides past the OD of the barrel, once for the stock bumps, and then for the new ones, which are actually tighter than original.... Once in place, the mag. protrudes that 0.084" past the left hand side of the receiver because it sits that much further to the left to line up....

Image

Here is a photo of the loaded magazine.... You can see the brass rotating pin, which I had to relocate, and the enlarged, kidney-shaped loading slot in the clear cover.... It functions perfectly, indexing to the next pellet each time you push one out.... I even tried it sitting on the end of my .357 barrel, and the pellet just slides right into the bore, exactly as it should.... Now that I have figured out how to do this, I will order another .25 cal MRod receiver and bolt, and a PRod trigger group and AR stock so that I can complete a third BRod in .357 cal.... I already have the bottle, tank block, and a spare FLEX tube, and most of the parts to make a valve.... so it looks like a regulated .357 BRod repeater shooting pellets is the next project.... although it likely won't get done until next winter, I am quickly running out of time as spring is here and the Motel will soon be busy....

Bob

_________________
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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 Post subject: Re: Tale of Two BRods
PostPosted: Thu Mar 22, 2018 7:42 pm 
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Location: Caronport, Saskatchewan
Great work Bob!! Quite the projects, thanks very much for sharing!

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 Post subject: Re: Tale of Two BRods
PostPosted: Thu Jun 28, 2018 2:42 pm 
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Location: Coalmont BC
I cast up the new NOE pellets today.... The mould comes with 4 sets of RG base pins, and they produce 3 skirted pellets and one solid with a flat base.... They look like this....

Image

The weights in 40:1 lead/tin alloy are 35.0, 37.0, 38.5 and 42.6 gr.... They all chamber perfectly in my .25 cal LW Polygonal barrel, but that is not surprising as I cut the chamber to allow for bullets as well as pellets.... I have my BRod set up with a Cothran valve and the WAR adjustable regulated tank block, set at 1900 psi.... I checked the velocity of all 5 pellets (including the JSBs) and got the following averages for one 8-shot magazine of each....

34.1 gr. JSB = 947 fps (67.9 FPE)
35.0 gr. NOE = 937 fps (68.3 FPE)
37.0 gr. NOE = 919 fps (69.4 FPE)
38.5 gr. NOE = 906 fps (70.2 FPE)
42.6 gr. NOE = 871 fps (71.8 FPE)

I was only shooting inside my shop, with the backstop 20 feet away, and all groups were one ragged hole, with no real difference between any of the pellets.... That is encouraging, because some pellets or bullets can't do that when shooting through the Chrony at that distance.... and those that do usually shoot pretty good at least out to 50 yards....

My summer is taken up with sitting at the Motel reception desk waiting for guests, and we are entering our busiest season now, so it is unlikely I will get to try these at distance any time soon.... but the velocity and energy is right where I want it for testing.... I can't wait....

Bob

_________________
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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 Post subject: Re: Tale of Two BRods
PostPosted: Tue Jul 03, 2018 5:03 pm 
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Location: Coalmont BC
My parts came in today from Joe at DiscosRUs, and I didn't waste any time whacking the front off the Gen2 MRod stock and grinding it out to fit over the WAR tank block.... Here is what it looks like with the Gen2 trigger installed also, plus a 500 cc 3000 psi aluminum bottle....

Image

I left the stock long enough to cover the tank block and the bonnet section of the regulator.... There is a bulkhead in the stock JUST in front of the front of the tank block when it is mounted in a WAR tube, so about 3/4" ahead of that is where I made the initial cut, and then ground it to fit with my Dremel....

I also purchased a .25 cal MRod receiver and bolt, which I will be modifying as before to fit the .357 cal TJ's 26" twist barrel I have, with a high-modulas CF sleeve glued over it to stiffen it, like I did with the .30 cal barrel.... I already have a modified .25 cal MRod magazine which will give me a 6-shot .357 cal repeater when it is all together.... I probably won't get much done before the winter, but at least I now have all the parts, other than the valve and hammer which I have to make....

Bob

_________________
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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 Post subject: Re: Tale of Two BRods
PostPosted: Sun Jul 08, 2018 5:49 pm 
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Location: Caronport, Saskatchewan
Awesome project!

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 Post subject: Re: Tale of Two BRods
PostPosted: Mon Jul 09, 2018 7:53 am 
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Location: USA, New Jersey
Cool thread! Thanks for sharing with this work!

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 Post subject: Re: Tale of Two BRods
PostPosted: Sun Nov 18, 2018 6:33 pm 
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Location: Coalmont BC
Well, the Motel busy season is over for another year, and it's time to hit the shop again.... As promised, the first order of business is to do a .357 version of my BRods…. The parts have been sitting on my bench gathering dust since the Spring.... it's been so long I had to sit down and think about where to start.... ::)

I decided to bore out the receiver for the 0.640" OD Hi-Mod Carbon tubing I used for the sleeve on the .30 cal TJ's barrel, as the .357 liner I have is the same 1/2" OD.... I had a hard time trying to drill it straight, for some reason this receiver just didn't want to run straight in my 4-jaw chuck.... so I drilled it undersize and then held it in my milling attachment, set it up with the bore of the receiver parallel to the ways and lathe C/L, and then used a 5/8" end mill to straighten the hole and move it over so that it lined up with the original 1/2" bore of the receiver.... It took a lot of fiddling, but the result was great, the outer sleeve and the barrel liner both slide into place perfectly.... The counterbored hole for the sleeve is 1.400" deep, so it stops just short of the 4-40 screw holes in the front of the receiver....

I then mounted the receiver across the lathe, in the milling attachment, and centered off the transfer port hole, drilled it out to 9/32" (0.281"), and counterbored it 3/8" x 0.150" deep for the transfer port.... That leaves 0.100" of receiver below the barrel, so the Teflon transfer port will seal against that shoulder with a slight amount of compression against that and the valve.... Travis assures me that you don't need to seal the transfer port against the actual barrel, that the set screw in the receiver that is directly above the barrel port pushes the barrel down against the receiver tight enough to seal OK.... I sure hope he's right about that, as there really isn't enough barrel wall to mill a 3/8" OD flat without hitting the bore.... A .357 barrel with a 1/2" OD only has a 0.070" wall thickness, which is one of the reasons for using the High Modulas CF tubing, to get the greatest stiffness possible for the barrel.... Here is what the receiver looks like at the moment....

Image

The Teflon transfer port will be 3/8" OD x 9/32" ID.... I chose that port diameter because it is 79% the caliber, which means I don't have to mill an oblong barrel port, I can just drill it.... It should be plenty big for a pellet shooter, IMO.... The plan is to build my own SS valve, with a matching exhaust port, and I'm going to try for a 0.323" throat on the valve (a size "P" drill), which with a 1/8" stem will give be about 12% more throat area than port area.... Using a 3/8" OD PEEK poppet I will have a 0.026" seat margin, which should work OK.... That will allow me to build the same "guts" for this valve as I did for my 6 mm and .257 valves last winter.... which will reduce the development time....

I'm looking forward to progressing on this build as time permits.... It certainly feels good to get back in the shop again.... It's been a loonnngggg summer.... ::)

Bob

_________________
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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 Post subject: Re: Tale of Two BRods
PostPosted: Sun Nov 18, 2018 11:56 pm 
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Location: Caronport, Saskatchewan
Glad to see you back at it Bob, congrats on a new season!

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 Post subject: Re: Tale of Two BRods
PostPosted: Mon Nov 19, 2018 8:00 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8972
Location: Coalmont BC
Two shop days in a row!.... WOO HOO !!!

Today I modified the .25 cal MRod bolt for this .357 cal build.... Two things had to change, the diameter of the bolt and probe, and the size of the lockup pin.... Crosman use an 8-32 SHCS for the bolt lockup in the .25 cal, and at the same pressure the .357 bolt will have twice the load on it.... Through the threads (the weakest point), a 10-32 has about 50% more shear strength than an 8-32, and I am only using about 2200 psi instead of 3000, so that is what I used.... The bolt is hardened, so I had to heat it to cherry red and let it cool slowly to anneal it.... Once annealed, I could drill and tap the hole out to 10-32 and mill a 1/4" flat for the head to tighten against, and I made a new locking pin from a 1/2" long SHCS with a nut screwed tight against the head to lengthen it.... I turned the head and nut down to 1/4" OD, and shortened it slightly so that it doesn't rub on the tube when the receiver is installed....

To make the larger probe, I used a piece of 3/8" CRS, and drilled it 1/4" to a depth of 3/4" and then shortened the stub of the bolt so that it just slid in full depth.... The OD of the new bolt nose was turned down to 0.356", and I made a longer probe that is 0.125" diameter (which just fits inside a JSB pellet) of the correct length to load the back of the skirt just ahead of the barrel port.... The shoulder between the two diameters I made a 20 deg. taper, which I figured won't restrict the flow, and will slightly reduce the chamber volume behind the pellet.... After taking the photo below of the parts, I installed the new bolt nose with permanent Loctite 638 (green)….

Image

The cocking slot in the receiver needed to be widened a bit for the larger pin, and because I use an 8-32 SHCS as my hammer pin.... The front of the slot on the left side also needed machining wider and deeper, to allow the bigger lock pin to properly lock up the bolt.... You can see those mods in the photo below....

Image

The other job I did today was to shorten the barrel and ream a new chamber.... The barrel was previously used in another receiver, but the barrel port position would not work for this build.... I already had a chamber reamer, so all I had to do was stone the cutting edge with a fine grit diamond file and cut the chamber deeper.... I left the barrel in the lathe because tomorrow I will cut the O-ring groove to seal the bolt before removing it from the chuck.... The photo below shows the completed .357 cal MRod bolt, the chamber reamer, and the tool I will use to cut the groove for the 1 mm x 9 mm O-ring....

Image

With a little luck, I will have the machining done on the barrel tomorrow, including the new barrel port, and be ready to glue on the carbon fibre sleeve....

Bob

_________________
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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PostPosted: Tue Nov 20, 2018 11:30 pm 
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Today I finished off the barrel by machining the O-ring groove, drilling the barrel port, and gluing on the CF sleeve.... Here is what the breech end looks like now....

Image

That 9/32" barrel port is pretty huge, and you can see how thin the barrel wall is with a 1/2" OD and a .357 bore.... I had to sand the outside of the CF sleeve slightly to get a nice slide fit inside the receiver, it was just a bit too snug.... There isn't a lot of room between the barrel port and the back of the barrel, another reason I had to use a tiny 1 mm CS O-ring for the breech seal.... I tried the bolt with the barrel installed in the receiver, and it slides into battery perfectly.... It loads a 78 gr. JSB pellet (which has a slightly deeper base cavity than the current 81 gr. version) nicely past the front of the barrel port.... It should also work perfectly with the new NOE Magnum Hunter pellet with the medium base pin (86 gr.).... The skirt of an 81 gr. EunJin pellet does not quite load past the front of the barrel port, so neither would the 81 gr. version of the NOE pellet which uses the deepest base pin.... I could not use a longer loading probe or it would not retract far enough to clear the mag. well.... This .357 build is really pushing the limits of an MRod receiver, the tolerances are virtually non-existent....

Before assembly with the Loctite 638 I sanded the outside of the barrel and the inside of the carbon tube with 100 grit to give them both some "tooth".... I had a nice slide fit, the barrel fell through the sleeve under its own weight.... Tomorrow, after the initial 24 hr. cure at room temperature, I will give the Loctite a post cure at 175*F for 3 hours.... Loctite is designed primarily for gluing metal, and this post cure makes a huge difference in the bond strength to a non-metallic sleeve.... Cured 638 has a shear strength of 4500 psi, which rivals the best epoxies.... While the barrel is curing I plan to make the new rear tube plug and SSG....

Bob

_________________
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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 Post subject: Re: Tale of Two BRods
PostPosted: Wed Nov 21, 2018 5:58 am 
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Location: Tecumseh, Ontario in South Western Ontario
The images for the Nov 19-20 posts didn't appear. At least not on my computer.

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 Post subject: Re: Tale of Two BRods
PostPosted: Wed Nov 21, 2018 12:21 pm 
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Location: Coalmont BC
Photobucket was having problems yesterday, I had to wait to upload the last photo.... They are working for me, and probably will for you the next time you look at this thread....

Bob

_________________
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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 Post subject: Re: Tale of Three BRods
PostPosted: Wed Nov 21, 2018 7:28 pm 
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Location: Coalmont BC
This afternoon I finished fitting the barrel to the receiver, adjusting the length of the back of the sleeve to stop the barrel in the correct place for the magazine to fit properly.... I use a 1/2" ID O-ring slid over the barrel against the end of the CF sleeve to provide a bit of resistance, so that I have to push it hard into the receiver to seat it, compressing the O-ring.... It will also seal the barrel to the receiver, should there be any slight leak between the barrel port and receiver port.... That won't help much, as any leak will be directed back towards the magazine, but it can't hurt.... I drilled a hole through the carbon fibre sleeve so that the front setscrew tightens against the steel barrel liner.... After fitting the barrel I fed one pellet from my modified MRod magazine into the barrel, and it worked perfectly.... You could feel a bit of resistance the last 1/8" as the pellet engaged the rifling.... Here is what the pellet looked like when pushed back out through the breech....

Image

You can see that the head of the pellet nicely engraves from the lands, but the skirt stops in the parallel portion of the chamber, as intended.... The next job was to make a new rear plug for the tube to hold the SSG I will be making.... This was an exact copy of the one I made for the .30 cal.... Here is a photo.... The bottom grooves are air vents to prevent any vacuum building up behind the hammer on firing....

Image

Tonight, after dinner, I will post cure the Loctite 638, and tomorrow I should be ready to install the barrel in the receiver.... That will complete the work on the .357 upper.... I still have to make a new SS valve, hammer and SSG for this build.... but I am very pleased with the progress so far....

Bob

_________________
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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 Post subject: Re: Tale of Three BRods
PostPosted: Thu Nov 22, 2018 3:55 am 
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Joined: Wed Oct 17, 2007 3:27 am
Posts: 2585
Location: Winnipeg, Canada
rsterne wrote:

Image

Bob


That is really nice. Is that from a complete end to end push through the bore?

Would be interesting to see how well that build groups when it's completed.

-D.S.

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