Canadian Airgun Forum

Nicely done sir! My milling attachment gives me about 2" of travel, so I'm always running into this sort of limitation. I started work on a bigger cross table last winter to try and break through some of those limitations - another job on the list of things that need finishing. I came to a halt when I realised I didn't have the die I needed, but that's in hand now.

40 MOA sounds like quite a lot of compensation - you have enough adjustment in the scope to bring in closer distances, or are you just concentrating on maximum long range performance?

The scope has over 140 MOA available (over 9 turns of the turret @ 16 MOA), so even if I choose to sight in at close range it will be less than half of it's available adjustment off center.... I will likely sight in at about 150 yards, which will give me from the muzzle out to well over 200 yards just using the MilDots.... and the ability to stretch out to about 500 yards without running out of adjustment and MilDots.... The 40 MOA is the calculated correction to put me dead on at 200 yards with the scope still centered.... The large amount of Elevation available is because of the 35mm tube on the monster Millet 6-25 X 56 SF scope (see Page 2 of 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!

This is one of those days you almost dread, and then feel great when it's over..... provided everything works the way it should.... The spacer between the two tubes is 10" long and concave on top and bottom to fit the 1-1/4" diameter tubes, and keep them parallel and 1/4" apart.... It could have been made from a piece of 3/4" x 1" aluminum bar stock, but the only piece I had long enough was 1-1/2" wide.... so the first thing I had to do was saw it lengthwise and then mill it to 1" wide.... Since it was 10" long and I can only machine a bit over 6" of length, that required two setups, and they were critical to match up parallel and exactly 1" wide.... Fortunately, that setup of the vice on the milling attachment on my lathe was also necessary for milling both sides to a radius using the 1-1/4" diameter router bit I just bought.... but again it meant two setups per side, critical that the part be square to the machine in both axis to end up with the same thickness at the center of the web from end to end, to end up with the tubes parallel in height.... and also with the grooves centered in the width of the part, to make sure the tubes end up parallel side to side.... I'm pleased to say that it went very well.... Here is the finished blank....



It fits the tubes perfectly, in fact better than previous breeches where I have machined the bottom with a ball-end mill.... I would definitely use a carbide router bit for this job again, especially with them being a fraction of the cost of a high-speed steel ball-end mill.... It needs to be run fairly fast, with not too deep a cut.... I was running 1270 RPM and removing 0.020" per pass once the full width of the router was engaged.... and using the power cross-feed, that was smoother than going by hand.... Including shallower finishing passes, that meant for about 15-17 passes per setup, times 6 (including milling the width to 1"), so about 100 passes.... It took me 5 hours to produce the piece you see above.... There is a bit more machining to do to this part, it has to be drilled for the transfer port and the three bolts that fasten the upper and lower tubes together.... plus a recess in one end to hold the back of the Forestock in place.... However, that won't happen until the tubes are finished and this will be machined to match.... Besides, I've had enough for one day.... It's time to have a drink and relax.... It's been a very productive few days, and it's time for a break....

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!

I received my new 33" Barrel today.... it slugged out right at 0.257" groove as requested, with a 7" twist.... I set to work fitting it to the Breechblock which I had previously drilled 1/2" all the way through.... I drilled the front to 33/64" and tapped it to a depth of 2" with 9/16"-18 NF threads, and then counterbored it 3/4" deep to 9/16" to fit the OD of the barrel.... The Barrel was turned down on the end to 3/8" to fit inside a steel Thimble which will carry the barrel port, next there is a 1/2" diameter portion to fit the bore of the Breechblock, and then the threads.... This was all done in a 4-jaw chuck so that it was concentric to the bore.... There is an O-ring which is compressed to seal the Barrel to the Thimble, and simultaneously seal the Barrel into the ID of the Breechblock when it is tightened against the Thimble.... Here is a photo of the Barrel machining, the roughed out Breechblock (made from 1-1/8" OD 2024-T3 round bar), and the two screwed together....





My hand is on the mend, it felt good to get back into the shop today.... Tomorrow I hope to turn the OD of the Breechblock to fit inside the upper CrMoly Monocoque tube.... Once the rough fitting is done, there will be a lot of work required to finish and mount the Breechblock in the Monocoque tube....

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!

Ah, I've got lathe envy again. No way I could handle that huge breech block in my Taig. Are you going to put any flats on the breech to make it easier to hold and index during the machining steps? With that block encased within the steel tube this is going to be one very rigid rifle! Very much enjoying the design and watching your progress.

Jim

Unfortunately, there is going to be a lot of accurate manual setup required as these parts are all too large to handle properly with my lathe with it's tiny milling attachment.... Wish me luck!!!

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!

What happened to your hand Bob?
I sure admire people who can think it all up on paper, then go do it themselves. I was in Busy Bee tools yesterday lusting over a nice Mill for $2000! DRO's, digital speedometer, and variable speed chuck without changing a belt!!

_________________
-Rick

Brocock Concept .22
3 Crosman MK 1 pistol .22

I sliced the base of my right index finger on a drill bit, pretty big gash.... but it's healing nicely....

Yesterday I got a piece of 1.5" black Delrin rod from Whitewolf (thanks, Kim!) and started turning it into a Buttstock today.... After a few attempts at trying to hold it, I managed to mill off both sides to leave me with a piece 1" thick, which I have drilled and tapped for the 3/8" threaded rod as shown.... It will soon look much prettier.... .... The other part in the photo is the partially finished fill fitting for the front of the Air Reservoir.... It is tapped 1/8" NPT on the front for a male Foster, and the holes for the four 1/4"-28 x 1/4" SHCS retaining bolts are drilled and tapped at 90*.... It needs shortening and the O-ring groove machined yet....



I usually use a 5C Collet in a square holder to drill holes at 90*, but the parts for this project are over 1" diameter, so they wouldn't fit.... The solution was to turn a 1" long x 1" diam. stub on the end of each part so that I could hold it in the collet as shown below.... The other parts below are the "Barrel Stretcher" which fits inside the front of the Monocoque tube, anchored by three 10-32 x 1/4" low profile SHCSs to stand the load of the Belleville washers that will put the barrel in tension.... and the mount for the Hammer Spring Adjuster which I made previously....



The upper (long) screw in the holder for the adjuster goes through the Breechblock (below the bolt) and the spacer, securing the rear of the two tubes together.... The shorter (lower) screw just mounts it into the lower tube, and will have a short piece of Delrin rod inside the hole pressing against the side of the 9/16" bolt that carries the spring guide, to lock the adjustment in place....

I also got the 10" long Breechblock turned to fit inside the Monocoque tube today, which prepares it for some of the machining to come.... I still have to make the Valve and Hammer.... Then comes the difficult job of machining the 4 foot long CrMoly tubes to hold everything....

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!

Your welcome Bob. Good to hear the hand is healing up well.

_________________
May the cry of the pack be with you upon your hunt

Whitewolf

This morning I finished up the Buttstock.... It turned out quite well, with lots of adjustment.... The LOP can be varied from 13-15", and the drop is adjustable over a range of 1-1/4" in 1/4" increments.... The shaft in the butt pad is 1/8" off center, so 1/2 turn changes the height of the butt by 1/4" and then there are three holes on 1/2" centers.... The threaded rod is glued and pinned into the butt pad, as well as threaded, and the wingnut locks the rotation....



This afternoon I did most of the machining on the Breechblock insert.... pretty much everything except the slot for the bolt handle.... I will have to duplicate everything you see here in the Monocoque tube, so accuracy and layout is the key here.... I'm quite pleased with the way it turned out....






The two holes with low profile 10-32 screws in them are to take the tension load of the barrel when the Belleville washer stack at the muzzle is compressed.... There are three screws that bolt the upper and lower tubes together, a 10-32 at the back and two 8-32s forward, either side of the transfer port.... The transfer port is milled at a 30* angle towards the muzzle to ease the flow transition into the barrel.... The Picatinny scope rail bolts to the Breechblock though holes in the Monocoque tube, with the forward screw tapped into the tube itself.... The opening for loading is milled flush with the centerline of the bore on the right side, and just past the vertical centerline, so just over 1/4 of the material has been removed.... This should make the assembly much more rigid vertically than milling out the entire top half of it.... There will be a steel thimble (actually in 2 pieces) that will have the barrel port, chamber, and loading tray machined into it.... The 8-32 screw under it will take the end force trying to push it back on firing.... It is set deeply so that the head is in shear for extra strength.... I will likely mill the slot for the bolt handle into both the Monocoque tube and the Breechblock in one operation after they have been assembled.... or possibly machine the tube first, then install the Breechblock into it and mill the slot through the slot in the tube.... I'm sure it will be the most difficult part of the whole procedure....

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!

Nice work, Bob.
I always found using a strip on 120 grit with the grit touching the Delrin to keep the Delrin from spinning or bring pushed backwards in the chuck. Also using a split collet works like a champ. I had a whole bunch made at work from 3/8" to 4". Aluminum or steel works great. I make them all in one operation so I know they run true.

_________________
-Rick

Brocock Concept .22
3 Crosman MK 1 pistol .22

The problem holding the Delrin was the size of the vice on my milling attachment, which is only 1" x 2.5".... but I got'er done!....

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!

Gotcha!
I picked a well made Cross-slide vise from BusyBee tools in Coquitlam on Tuesday. 4" wide jaws and opens to 4". Travel was 3 1/2" by 3". Should work great with the good quality Drill press the in-laws are getting me for Christmas.

_________________
-Rick

Brocock Concept .22
3 Crosman MK 1 pistol .22

I may have one of those under the bench (it's Busy Bee, not sure of the size but sounds similar, I've never used it), but my Drill Press is WW2 vintage RCAF surplus, just a mount for a portable 5/8" x 300 RPM Black & Decker.... it wobbles all over the place but MAN has it got torque....

Today I machined the double convex Tube Spacer to match the breechblock, as the mounting screws and transfer port penetrate it to connect the two tubes.... The recess in the middle is a pocket to clear the barrel tensioning retainer screw....



On the bottom at the front I had to machine a recess that will hold the Forestock tube in place tight against the top of the Reservoir.... you can see it in the photo below.... I also got the Hammer made today, including the cocking handle, as shown....



The total weight of the hammer and handle is 182 grams, and it will have a total travel of 1.5".... The captive spring arrangement and adjuster was shown previously, and the moving part weighs 53 g. for a total of 235 g.... That means that only 77% of the total energy ends up in the hammer, the rest is absorbed by the O-ring on the guide when it comes to a halt before the hammer coasts the last bit to open the valve.... That is the price you pay for easier cocking and less hammer bounce....

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!

Today I attached the Front Cheekpiece Mount to the back of the Breechblock....



It is mounted below the centerline of the tube so that the inside of the Cheekpiece tube sits against the top of the upper Monocoque tube.... I also machined the front of the barrel to fit the 1/2" ID Bellevilles and threaded it 1/2"-20 NF for the nut that will provide the barrel tension.... The aluminum sleeve that bolts into the front of the Monocoque tube is 9/16" ID to fit on the larger part of the barrel, while the Bellevilles ride on the 1/2" section....



The front of the Monocoque tube is about 1/10" ahead of the muzzle to protect the crown.... If I wish, I can use a Hatsan Air Stripper instead of the nut to tighten against the Bellevilles to provide the barrel tension and also strip the air away from the back of the bullet....



This completes all the parts that fit inside the Monocoque tube.... except to machine the bolt slot which I will do after machining the tube.... I am still undecided if that will be my next step, or if I will make the valve first.... and put off machining the two tubes until the end....

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!