Over the past few weeks I have been collecting the necessary parts for this new project.... Here is what I have purchased as a starting point.... I bought a Disco main tube and valve, the hammer and gauge block from a PRod, a trigger and guard from an MRod, a Disco Double kit and MRod trigger shim from Lloyd at Air-Gun-Lab, and a Boyd's Blaster stock in Camo from Norm at Discos-R-Us inletted for the Disco Double kit and MRod trigger.... I wanted to start from the best possible components to achieve my goal....
The main purpose of this project is as a test bed for the new .30 cal barrels that SeanMP and I are having made for the new JSB .30 cal pellets.... These pellets are smaller than the 0.308" standard used by Powderburners, having a head size of only 0.300", so we have designed a new barrel to match.... They will be available in a 25" length to fit on the Disco and allow enough room for a muzzle brake or air stripper to be attached.... The barrels will be 0.50" OD, which will allow their use in a .25 cal MRod as well as a new repeater breech that I have designed and Sean will be making.... The breech will also accept a .25 cal barrel with a 0.50" OD, and make use of the 8-shot .25 cal MRod magazines, both stock for the quarterbore version, and enlarged to .30 cal (with 7 shots) for the bigger caliber.... The magazines will accept pellets or cast bullets up to 0.48" long.... Those can be stabilized in a .30 cal barrel with a 26" twist, which is ideal for the JSB pellets, so that was our choice.... The mandrel had been made, and we will be placing an initial order shortly....
In terms of potential performance, we're pretty much flying blind here at the moment.... My initial goal was ~850 fps with the 46 gr. JSBs (74 FPE), and while that remains a realistic performance level to get a decent shot count, I'm hoping that during development I may see that power level in .25 cal and about 88 FPE in the .30 cal, but at what pressure remains unknown.... Ideally, I would like to achieve 14 shots (2 clips) with the .30 cal using the Disco Double tube setup.... which would mean 7 shots (1 clip) on a standard Disco.... As the market for quarterbore rifles is likely way larger than for a .30 cal, we are trying to reach a compromise between the two, allowing as many components to be shared as possible.... and also for the minimum changes to Disco components.... It's a given that the valve needs to breathe a lot better, so that will be the place I start.... I will try the PRod hammer (without the extended striker) and my heavy Disco hammer spring, but I doubt they will be up to the job, so we anticipate making a heavier hammer with longer travel, and using a QB hammer spring to move enough air, particularly for the .30 cal.... An RVA will be part of the package, of course....
The new 7/8" wide, 6" long breech will be designed around the .25 cal MRod magazine, and will incorporate an additional mounting band at the front, located between the trigger and gauge.... This will provide exceptional rigidity for a floating barrel, although a barrel band may also be used if desired.... The top of the breech will be grooved full length for dovetail mounts.... It will be significantly taller than a Disco breech (to allow for the magazine), so for appearance it will incorporate a mount for a 7/8" OD Carbon Fibre shroud and a Hatsan-style air stripper.... The end of the barrel will be threaded, and when the air stripper is tightened against the end of the shroud, it will put it in compression, putting the barrel in tension.... The muzzle blast will be vented out through the stripper, and not into the shroud, so that legality will not be a question in Canada.... For those allowed to have quieter airguns, there will be clearance for a longer 1" OD shroud.... although the barrel tensioning feature will be lost of course.... It is hoped that 0.59" OD barrels will be available for QBs and Sean may even work on a repeater breech for them as well at some future date....
While we're on the subject, I want to make it clear that I will not be involved in the marketing of these barrels, breeches, and other components other than in doing the design work and prototyping.... Manufacturing things and selling them is Sean's bag, not mine.... so I ask that any inquiries in that regard be addressed to him.... My compensation is solely the satisfaction I get from making things work they way they should.... at which point I move on to the next project.... I have no interest in repetitive operations, nor do I have the time to do them....
Bob
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. Placed the order before all this talk of these new breeches started.
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