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 Post subject: Tale of Two BRods
PostPosted: Sat Jan 07, 2017 2:10 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8979
Location: Coalmont BC
I have a couple of other projects to finish up, but I wanted to give you a tease about a new project I am about to start.... I have been collecting the parts for nearly a year.... It all started when Travis at W.A.R. was moving his shop and decided to "clean house" and send me a big box of parts.... When I opened my "surprise package" I was pretty enthused with the contents, and could see a lot of the parts required to build two Bottled Marauders.... I scraped together enough money to buy the remaining parts I didn't plan on making myself, and the results of this collecting of bits and pieces is shown below....

Image

Above are the parts for a Traditional rifle, using the beautiful stock that Travis supplied.... He also sent me two main tubes, a drop down, and a ton of other parts, including a bunch of valves, one of which (shown) I modded by moving the seat forward and increasing the ports to 7/32" (0.219").... I purchased two receivers from Crosman (through Lloyd Sikes), along with the Gen 1 MRod trigger group.... Below are the parts for the Tactical version.... I purchased another drop down from Travis, the PRod trigger group through Lloyd, and he graciously supplied me with the AR style Buttstock to help this project along.... The valve is a Cothran Powerhouse, which will be used in one of the builds....

Image

Below is a photo of the tank options I have available.... At the rear is a 500 cc, 250 bar (3625 psi) tank from England, next a regulated 3000 psi 500 cc from Travis, and in the front another 500 cc 3000 psi, but with an adapter to fit directly to the drop down, so that it can be used unregulated.... Travis also supplied me with an adapter for the Metric 250 bar tank as well....

Image

I haven't completely decided on the calibers yet, I have several barrels to choose from.... I have a .25 cal LW Polygonal, a .30 cal TJ's, a .308 PB barrel, and a .357 cal TJ's.... I have obtained some 1/2" ID high-modulas Carbon Fibre tubing with a 0.64" OD.... Sleeving the TJ's liners with that would increase the stiffness to at least equal to a steel barrel with a 5/8" OD (the diameter of my other barrels).... and I have determined that I can bore the front of the MRod receivers out to that size forward of the two 4/40 mounting screws.... which will allow me at least 2 diameters of support for the larger barrel inside the receiver for a very rigid, free-floated barrel installation....

All the parts will be interchangeable.... I plan to end up with two receiver/barrel assemblies, which can mount on either main tube.... One tube will contain my modded MRod valve, with suitable hammer, spring, and SSG.... while the other will contain the Cothran valve, with the optimum parts for that.... and both will have their own drop down, a complete, ready to go, pressure assembly, minus tank.... Any of the three tanks can be used on either main tube.... Onto each the main tube, I will be able to attach whichever trigger assembly and stock I wish.... I will be making a rear mount for the AR stock that will contain the SSG, of course....

Anyway, that's what my next major project is.... I hope you enjoy following along as it progresses.... My thanks to Travis, Lloyd, and Don for their assistance and generosity....

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: Sat Jan 07, 2017 3:10 pm 
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Joined: Wed Feb 17, 2010 6:04 pm
Posts: 841
Location: Nova Scotia
I will follow along, I like to see a bunch of parts come together so the final product is better than the sum of its parts.


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 Post subject: Re: Tale of Two BRods
PostPosted: Sat Jan 07, 2017 7:37 pm 
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Joined: Fri Jul 08, 2016 8:52 pm
Posts: 39
Location: Chilliwack, B.C.
I'll be watching closely, too. Looks like fun.


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 Post subject: Re: Tale of Two BRods
PostPosted: Sun Jan 08, 2017 8:01 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8979
Location: Coalmont BC
I got around to measuring the plenum volume in the tubes today.... There is 69 cc between the back of the tank block and the front of the valve.... However, in my drilled out MRod valve there is another 4 cc (even more in the Cothran), and in the tank block, which has large passages, there is about another 8 cc.... so the total is over 80 cc.... That means the plenum is large enough for any .25 cal or for a .30 cal pellet shooter for sure.... and for a .257 cal or .30 cal bullet shooter, or .35 cal pellet shooter it is large enough that it would only take about another 100 psi bump in the setpoint to make up for any lack in plenum volume.... It is, however, on the small side for a .308 or .357 bullet shooter, or anything over about 160 FPE, so for those an unregulated setup would be indicated.... The good news is that the passages through the tank block, and the brass tank adapters, are large enough that without the regulator in between, the entire 500cc tank becomes part of the reservoir, able to keep the pressure up during the shot.... This means the effective reservoir is about 580 cc (35 CI) when unregulated....

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 Jan 10, 2017 10:12 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8979
Location: Coalmont BC
I worked on the tubes today.... The tubes that Travis sent me are intended for Gen 2 MRod parts.... I have two Gen 2 receivers, but I wanted to be able to interchange the tubes from traditional wood stocked rifle to a tactical setup with pistol grip.... Since that needed a PRod trigger group, and it is the same bolt pattern as the Gen 1 trigger, I had to redrill the tubes to accept the Gen 1 and PRod triggers.... In addition, the transfer port hole in the top of the tube had to be drilled out to 3/8" to accept the larger transfer ports.... Here are the redrilled tubes, with the new holes circled....

Image

The front two holes on the bottom are drilled and tapped with 8-32 threads, while the rear hole on the bottom is the clearance size for an 8-32 (11/64"), because the rear trigger screw threads into the rear tube plug.... A custom rear plug will be required because the bolt pattern is Gen 1 on the bottom and Gen 2 on the top, to accept the two rear 4-40 screws that hold down the receiver.... The only change on the top was drilling the original TP hole out to 3/8" in the same location....

I installed the male Foster and gauge in the tank blocks (drop downs), along with a 1/4"-NPT flush plug on the bottom.... I want to be able to tether the guns without having to waste all the air to fill the 500 cc bottles during development, so I made a blanking plug for the tank/regulator mount in the drop down from an old regulator bonnet....

Image

I simply removed the pin valve and drilled and tapped the bonnet for a 1/8"-NPT flush plug to seal it.... I installed a couple of 5/8" long 10-32 SHCSs in the threaded holes in the bonnet and screwed them in until they touched each other in the middle.... This gives me something to grip better with my fingers to screw the blanking plug into the front of the tank block.... You can see the O-ring that seals the regulator bonnet to the tank block sitting on the bonnet.... It seals in the recess in the front of the tank block, instead of way down inside, so you don't use an O-ring in the normal location on the bonnet.... Travis is to complimented on this arrangement, it certainly is a lot easier to machine, and less prone to leaks, IMO.... I then installed the valves in the tubes, and threaded in the drop downs, stopping with them pointing downwards, lined up with the trigger group.... Once there is pressure inside, they won't have any tendency to rotate, and it isn't important for them to be screwed up tight against the end of the tube (and it you do, they won't line up with the trigger on the bottom of the tube.... You simply screw them in all the way and then back them out until they line up with the trigger.... I then installed my blanking plug and checked for leaks.... Here is the assembly, which I will leave overnight to make sure it holds pressure....

Image

For the eagle-eyed amongst you, you will notice that the gauge is showing over 3000 psi.... I filled the tube to 3000 psi exactly with a known gauge, but this one shows 3500.... In fact, it was 500 psi high all the way from the start of the fill.... Does anyone know if that is an MRod gauge?.... Anyway, it's nice to get a start on this project, other than just collecting parts for it....

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 Jan 12, 2017 8:31 pm 
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Joined: Wed Jul 01, 2015 2:14 pm
Posts: 305
Location: Manitoba
Looks to be a MRod gauge, the one on my brother's rifle is reading about 400psi high.


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 Post subject: Re: Tale of Two BRods
PostPosted: Thu Jan 12, 2017 8:51 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8979
Location: Coalmont BC
A guy on the GTA (bnowlin) told me how to fix the gauge (it is an MRod gauge).... you squeeze the housing across tow of the flats, near the lense, with pliers or a vice.... This will cause the lense to pop up on one side 90* to the pliers, and then you can flip it out.... Rotate the white card with the numbers until the gauge agrees with a known accurate gauge and replace the lense....

I found my card had a small drop of glue holding it from rotating, which I had to cut with an X-acto knife.... I used a new drop of glue after I reset the gauge and before I replace the lense.... Works perfectly now, within 100 psi from 500-3000 psi....

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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 Profile  
 
 Post subject: Re: Tale of Two BRods
PostPosted: Thu Jan 12, 2017 9:00 pm 
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Joined: Wed Jul 01, 2015 2:14 pm
Posts: 305
Location: Manitoba
Well thanks for that Rsterne, I will be doing just that to my brother's gauge.


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 Post subject: Re: Tale of Two BRods
PostPosted: Thu Jan 12, 2017 9:12 pm 
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Joined: Wed Jul 01, 2015 2:14 pm
Posts: 305
Location: Manitoba
Did you remove the gauge from the gun when you did the adjusting?


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 Post subject: Re: Tale of Two BRods
PostPosted: Thu Jan 12, 2017 10:20 pm 
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Joined: Wed Jul 01, 2015 2:14 pm
Posts: 305
Location: Manitoba
Got it thanks.


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 Post subject: Re: Tale of Two BRods
PostPosted: Thu Jan 12, 2017 10:48 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8979
Location: Coalmont BC
Actually, robertr, I didn't remove the gauge, but there was no air in the tube, I had previously determined how much I needed to move the number card....

I started working on the receivers today.... On most of my projects I have to make them from scratch, but for this project I started with two .25 cal MRod receivers and bolts.... The first thing to be done was to drill out the transfer port hole to 3/8" OD, the same diameter as the Cothran valve, and the holes I drilled in the tubes to match.... I plan to use a piece of 3/8" OD Teflon rod, drilled as appropriate, for the transfer port.... So, I set one receiver up on my milling attachment on my lathe, using a stop at one end to minimize the setup on the other one, centered off the existing transfer port hole, and drilled it out to 3/8".... I then took it out of the vice on the milling attachment, put the other one in, checked the hole center, and drilled it as well....

I had decided to drill the front of both receivers to 5/8" for about 1-3/8" deep, staying in front of the two 4-40 screw holes, so that the full diameter part of the barrel will be held rigidly in the receiver.... It doesn't do a lot of good to have a 5/8" barrel and then turn it down to 1/2", all it will do is flap around (bend) where the receiver starts.... I planned on using my 4-jaw chuck, holding the back of the receiver, and drilling the front with a 5/8" drill in the tailstock, but I found that the receiver is VERY flexible where it is machined away for the magazine, so much so I was afraid that it would not run true, and if the drill grabbed, it might bend and destroy the receiver, so I needed another plan.... I chucked a piece of 1/2" cold-rolled steel in the chuck, which was a perfect slide fit in the front hole of the stock receiver.... I then mounted the receiver in my milling attachment vice so that the steel rod rotated and slid back and forth freely, so that insured that the chuck was lined up with the barrel hole in the receiver.... I then simply drilled the hole out with a 5/8" drill to a depth of 1.4" to the shoulder of the drill.... The LW barrel is actually 16mm, which is a few thou over 5/8", and it slid perfectly into the drilled hole.... I drilled the other receiver the same way, and it turns out that the CF tubing I have is also 16mm OD, so it also fits nicely into the new, larger hole in the front of the receivers.... Here is what they look like now....

Image

I then checked to make sure that the stamped end of the LW barrel was, indeed, the breech, by measuring the land diameter with my new small hole gauges.... I found out that the land diameter at the breech is 0.247" and at the muzzle it is 0.244", so the barrel has a 0.003" choke.... I machined the breech down to 1/2" OD for 1.5" of length, and checked how it fit into the receiver.... With an O-ring against the shoulder of the barrel, sitting against the drilled shoulder in the receiver, the back of the barrel was about 0.010" too far back for the magazine to slide into place, which I left for now.... I then used a chambering reamer I made several years ago for the LW barrel on my Hayabusa, and machined the chamber and leade to the required depth so that the front of the chamber is just ahead of where the front of the barrel port would be located.... I checked what a bullet and pellet looked like chambered to that depth, and was pleased with the results, so carried on with the next step, which was laying out the barrel port....

I carefully measured the location of the port from where the back of the barrel needed to be to fit against the locating hollow in the magazine, added a 0.010" (because I knew I had some extra length available), set the barrel up in my milling attachment, carefully centered it relative to the chuck, and drilled and milled the barrel port and the 3/8" diameter flat for the transfer port to seal against.... The port transitions from a 1/4" diameter at the TP spot face to 3/16" wide by 5/16" long at the bore line, so I actually can use up to a bore size transfer port should it be required.... After the milling, I touched up the port with a small ball in my Dremel, blending the 1/4" round port into the oblong barrel port, within the thickness of the barrel itself.... I then slid the barrel into the receiver, lined up the transfer port spot face with the hole in the receiver, and tried the magazine.... As expected, the barrel needed to be shortened 0.010" for the magazine to slide into place....

The last step on machining the back of the barrel was to machine the internal O-ring groove to seal the bolt.... If anyone else attempts this build, the location of that groove is CRITICAL.... The groove is 0.070" wide to fit the O-ring, and from the back of the TP spot face to the back of the barrel is only 0.125", so there is only 0.055" of material left TOTAL for BOTH sides of the groove.... The force on the O-ring from air pressure, is backwards, so I left more material there, 0.035", which only leaves 0.020" between the front of the O-ring groove and the back of the TP spot face.... and YES they would intersect if you put the groove too far forward in the barrel.... Anyway, knowing that was an issue, I was careful and all went well, the bolt slides nicely through the O-ring, and the barrel now looks like this....

Image

I assembled all the parts so far, just so that I could have a look, and take a photo so that you can see the progress, and the proportions....

Image

I'm very pleased with the progress to date, so I guess it's time to make the hammers and rear plug and SSG next....

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 Jan 12, 2017 11:13 pm 
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Joined: Wed Jul 01, 2015 2:14 pm
Posts: 305
Location: Manitoba
It did not take much pressure to get the lens out.
That is going to be a cool looking gun when you are done, Do you foresee any problems with the Bullpup stock because of our laws?


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 Post subject: Re: Tale of Two BRods
PostPosted: Thu Jan 12, 2017 11:17 pm 
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Joined: Wed Jul 01, 2015 2:14 pm
Posts: 305
Location: Manitoba
Looking at the stock again I guess it would not be a Bullpup unless the action was to the rear.


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 Post subject: Re: Tale of Two BRods
PostPosted: Fri Jan 13, 2017 12:07 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8979
Location: Coalmont BC
I've already modded the stock to accept the MRod trigger group, and there will be a new comb attached where IF the stock was a Bullpup stock (who says it is?) the action would be.... At this point in time, it's just a fancy piece of wood that cleared Customs no problem.... :lol:

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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 Profile  
 
 Post subject: Re: Tale of Two BRods
PostPosted: Fri Jan 13, 2017 5:46 pm 
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Location: Coalmont BC
The plan today was to get started on the hammers, but I decided instead to finish off the barrel and receiver.... I marked the locations for the spot faces for the setscrews on the top of the barrel and drilled those.... I installed the bolt and discovered I was missing parts yet again (that's what happens your first time playing with parts from a gun you have never worked on before).... I had to make the small plate that prevents the bolt from over-rotating yet allows the handle to be left or right.... no big deal, just time.... Fortunately I still had some small 2-56 screws left over from my R/C Yacht days to install it.... Once I installed the cocking pin in the bolt I could check the position of the shoulder on the bolt and the length of the probe, and the shoulder was too far forward and the probe too short.... I had heard that the bolt was hardened, so I heated the front cherry red and let it cool slowly, but it was still too hard to drill for a new probe.... I figured it might be just case-hardened, so I ground the tip off the bolt, and sure enough that allowed me to get a bite with a small drill....

Mounting the bolt straight in the lathe chuck was tricky because of the handle and the short mounting surface around that, which is the only place to grab it.... I came up with a neat trick to hold it straight while I tightened the chuck up.... I held the bolt probe in the tailstock Jacob's chuck to hold the end of the bolt centered, ran the handle end into the 3-jaw until the handle touched the chuck face, between two of the jaws, and then tightened the chuck good and tight.... When I undid the tailstock chuck and backed it away and mounted a tiny center drill, it was perfectly centered on the end of the probe where I had ground away the case hardened surface.... I drilled a small center hole, and the changed to a 3/32" drill and drilled in about 3/4".... I then removed the bolt from the chuck and ground the probe off, back to the tapered shoulder, and ground the tapered portion off to get through the case hardening there as well.... Of course since I had previously drilled a hole for the new probe, I had a center hole so that I could use a 60* center in the tailstock and line up the bolt again in the 3-jaw in the headstock.... I checked that it was running straight (it was), and then faced off the shouldered portion of the bolt square.... I checked it for length, and decided I would just put a very slight conical taper on the face from the OD to the probe hole.... This puts the edge of the shoulder flush with the back of the barrel port.... I then used a piece of 3/32" drill shank, glued it into the hole in the bolt, and then cut it to length for the new probe.... I made the probe long enough to seat JSB Kings with the skirt flush with the front of the barrel port.... That puts the King Heavies about 1/16" further forward, because they have a shallower hollow in the base, and a cast bullet would sit with the base 1/8" ahead of the front of the barrel port.... You can see what the probe looks like in the photo below....

Image

I calculated the remaining area for airflow around the probe, and it works out to the same as a 15/64" transfer port.... I will likely be using a 7/32" port, which is the same size as the exhaust port in my modded Mrod valve (0.219"), so unless I have to go to full area porting should offer no restriction to the flow.... If I do have to use full 1/4" ports, I may have to change to a flat nosed bolt that retracts into a J-slot to allow maximum flow.... but I don't anticipate it, as I'm not trying to build a 100 FPE quarterbore....

At the muzzle I wanted to mount a Hatsan Air Stripper, as I happened to have a spare .25 cal on hand.... This required turning the barrel and threading it 1/2"-20 NF for the stripper.... I found a position in my 3-jaw where the bore ran true, and then faced the muzzle off square to the bore, and then turned the barrel OD down to 0.50" for a length of 0.80" and threaded it.... The photo below shows the installation....

Image

Anyway, I think the upper assembly for the .25 cal version is now complete, and I can get on with the hammer and spring arrangement....

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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