Canadian Airgun Forum

Nice receiver Bob

What about threaded barrel? could thread it at full 9/16" then Loctite a threaded sleeve as required for a no tension setup?

Walter...

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Walter

I'll think about that, Walter.... see if I can work it around the plans for a thimble....

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!

I made the thimble and machined the barrel to fit it today, and made the collar to hold the barrel into the breech.... Thanks to Voltar1 for the idea of threading the barrel and the collar instead of silver-soldering it.... it worked like a charm.... You can see how the tubular compression nut will push on the collar to hold the barrel in place in the breech.... Also shown is the new bolt, a retractable, probeless design.... It pushes the bullet past the barrel port and then pulls back clear of the port to maximize flow....



For those of you not familiar with a thimble, here it is slid off the end of the barrel.... Basically the port and bolt sealing O-ring are in the thimble, which is held into the breech with one setscrew.... The barrel is free to rotate inside the thimble, which will allow you to index it for best accuracy.... You want the barrel rotated so that it vibrates up and down instead of sideways.... Rotating the barrel will cause the POI to move in a circle on the target.... If it is locked in place at the bottom of the circle, the vibration has to overcome the weight of the barrel, so in theory the groups will be smaller.... The end of the barrel is just ahead of the barrel port, and the chamber and leade are machined in the barrel.... It seals to the thimble with a single O-ring.... In my case, the thimble seals to the valve with a tubular transfer port made of 3/8" Teflon rod that is drilled to bore diameter.... The barrel port is oblong to maintain the area without causing loading problems....



I found the correct location for the collar, marked it, and installed it with Loctite 638 (green) retaining compound, so it now permanent.... I will dress the OD true to the barrel tomorrow and then I can fit the barrel to the breech for the first time.... I still have to chamber it and cut the leade, plus do the machining at the muzzle to hold the Bellevilles and Air Stripper....

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!

Is there a 2nd o-ring to seal around the bolt? Wondering where/how that is retained. I thought for a moment that it would be sandwiched between the end of the barrel and a step in the ID of the thimble, but that would put it on the wrong side of the port. Maybe the thimble presses against a reduction in the bore of the breech, just before the loading tray? That would give a place to put an o-ring on the right side of the port, but would mean you'd have to reach from the front of the breech to just in front of the loading trough with an end mill. Looks like a bit of a strech.

Jim

There will be an O-ring groove inside the thimble, like an MRod (it's in the barrel).... It's a bit tricky to grind a tool to cut it, but once that's done it's an easy job, actually.... It is in between the back of the transfer port flat and the back of the thimble.... lots of room, actually.... I use this setup almost exclusively now, and it's the only way to seal a retractable bolt....

I actually have installed an O-ring between the end of the barrel and the breech (in front of the loading tray) on all the other versions of my Hayabusa Mk. II.... You don't need to cut the seat square with a mill, the tapered shoulder on the end of a drilled hole works just fine....

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!

Ah, I see. Yes, I could imagine that is a tricky tool to grind - nice to have though.

Cake walk....don't grind it....turn it.

http://madmodder.net/index.php?topic=3523.msg42239

Download the pdf at the end of the first post. Made the internal threading tool and grooving tools from drill rod....works in cold rolled quite well.

Al

Might be a bit tricky making one of those to put an O-ring groove inside a .22 cal barrel, but what do I know.... I just used a piece of 1/4" square tool steel and a Dremel cutoff wheel and a grinder.... ground away everything that didn't look like a tool bit....

I have one for standard 0.070" cross section O-rings and another for 1mm.... You have to be careful to allow clearance for when it moves into the work, of course....

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!

I've scratched my head trying to work out how I could do it on one of the Crosman 177 barrels and came to the conclusion I couldn't. I think for that I'm probably stuck with sandwiching an o-ring between the end of the barrel and something else. It's the something else part I haven't quite figured out yet

Still, I've saved the pdf from that link for future reference - it looks useful.

I didnt find too much trouble for building an internal cutter gor .22 cal. Kinda combined from what both Al and Bobs makings. But when it came to building one for .20cal was a different story. I found that the slightest chatter engaging the rifling would break drill stock or tool steel. I sought the advice of a machinist I have used in previous years for my work side of life. He was busy and a quick of what I tried and results was told leave it with him. To check out. Subsequently he cut the oring groove for me using a Colbalt rnd rod as the cutter. Turned same manner as what Al suggested. When I quizzed him about a cutter for .177 his response was Incoloy. So different metals to strength to diameter ratios.

Sorry about the side track Bob. Contiinue. Following your findings upon tne 7mm bbl. Mine still after 10months is still waiting upon testing with the Condor platform way too many things in the way. Hence my close following....

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

Whitewolf

Today I pretty much finished up the barrel.... I fitted the sleeve to the breech and machined a groove in the middle of the threads for the setscrew to limit barrel rotation once I find the right spot.... Then I turned down the muzzle for the Bellevilles and threaded it for the Hatsan Air Stripper, and made the collar to put the shroud in compression.... Here is the assembly....



Here is the assembled breech....



Here is the muzzle assembly....



and here are the parts used at the muzzle....



The shoulder that the shroud will sit on is 1" long at both ends for stability.... The tension on the Belleville washers is provided by tightening the Air Stripper.... Those are the stiffest Bellevilles I could get, capable of 1335 lbs. force when flat.... although I don't expect to have to use that much to find the "sweet spot".... I have another set of Bellevilles that are 600 lbs. flat load.... The only jobs I couldn't finish were machining the O-ring groove in the thimble (the 7.5mm x 1.5mm O-rings aren't here yet) and chambering the barrel (no bullets yet).... I'm also waiting for the 25mm OD x 22mm ID Carbon Fibre shroud tubing.... So, now we wait....

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!

Great progress Bob. Really looking forward to seeing how this shoots.

The Carbon Fibre tubing for the shroud came in, and I cut it to length and installed it.... I think it looks quite nice....



In the photo below, the Air Stripper is tightened exactly one turn from when it first contacts the Bellevilles.... That applies 750 lbs. of tension in the barrel (and compression in the shroud).... I plan to leave it under that load for a week and see if the gap in the Bellevilles increases, which would indicate that the CF tubing is compressing over time....



I don't think that the Bellevilles are unattractive at all, in fact in combination with the Stripper it gives quite a unique and purposeful appearance to the muzzle, IMO....

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!

I agree... it looks very nice Bob

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"A candle loses nothing by lighting another candle"

Bob?
How do you arrive at 750 lbs? Torque wrench? Is that ft lbs or inch lbs?

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-Rick

Brocock Concept .22
3 Crosman MK 1 pistol .22