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Thread: New .30 cal Barrels for JSB Pellets

  1. #1
    Moderator rsterne's Avatar
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    New .30 cal Barrels for JSB Pellets

    I'm just going to let the cat out of the bag a bit here.... SeanP and I have decided that since JSB are making pellets for the FX and Daystate .30 cals that are smaller than will properly fit in a "standard" .308" barrel (LW, TJ's or PB).... we are ordering a mandrel from Mike at TJ's to have airgun barrels produced to properly fit the new 46-50 gr. JSB pellets, which have a 0.300" head diameter.... Once the mandrel is made, we will be getting some barrels done in 0.50" OD which would fit an MRod, and I will be doing a prototype riser breech to adapt that size barrel to a 22XX/Disco using a modified MRod .25 cal clip (Lloyd's) that will allow 7 shots in .30 cal.... This breech will also accept a .25 cal MRod barrel, or a .25 Auto TJ's barrel blank as well.... We already know that the .25 MRod clip will accept the 53 gr. cast Lyman bullets and the 50 gr. Mr. Hollowpoint bullets, so if all works out as planned, both the MRod and 22XX/Disco platforms will move up to shooting 46-53 gr. pellets/bullets in both .25 and .30 cal....

    SeanP is hoping to produce the breeches & bolts, along with providing machined .30 cal barrels, and valves opened up to provide the additional airflow required.... I'll be doing the prototype work, and at the moment FPE numbers are just a guess, as we want to make everything as much of a "drop-in"/"bolt-on" as we can.... However, my goal is 850+ fps with the 46 gr. JSBs which would be 74+ FPE and hopefully more depending on the pressure and barrel length used.... There is no reason that shorter .25/.30 cal barrels could not be fitted to the 2240/50 pistols as well, using the new repeater breech.... Down the road, SeanP may get some 0.59" OD (15mm) blanks made and machine them up for a single-shot conversion for the QB 78/79 rifles as well.... along with matching bolts....

    Please don't bug us, as it will be a while before any of this gets prototyped, let alone into possible production.... The above information is all I can supply at the present time.... My prototype will be a new project, which is a .30 cal Disco Double (from Lloyd at AirGunLab) in a Blaster stock with an MRod trigger (from Norm at DiscosRUs).... When I have anything concrete to report, it will be in a thread I will start on that project....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

  2. #2
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    Bob, with all the talk about the accuracy of the smooth twist barrels would it make sense to have Mike to copy a 30 cal smooth twist barrel ?

  3. #3
    Moderator rsterne's Avatar
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    I'm not sold on the smooth twist idea.... So far, they aren't cleaning up in bench-rest contests.... and SeanP and I certainly don't have deep enough pockets to do the research necessary....

    What is really interesting about the smooth twist barrels is that the twist of the rifling pressed into the muzzle is "normal" - ie about 16-18" twist.... You can measure that from the photos of them being made and calculate it.... However, the "spin rate" of the pellets is MUCH slower, as if they are coming out of a barrel with a twist rate of 40-160 inches, depending on who tests them (and likely the velocity and harndness of the pellet).... In addition, there is virtually NO marks on a fired pellet from the rifling, or should I say that the rifling is "smeared".... Those two things can only occur (IMO) if the pellet is "skidding" across the rifling and smearing because it is only picking up a small portion of the rotation it would have if the rifling was full length.... The resulting twist rate is so slow that were it not for the drag stabilization of a waisted pellet they would surely tumble....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

  4. #4
    Senior Member Doc Sharptail's Avatar
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    Very cool news. I'll be watching for your progress reports. Here's wishing you guys success, with no flies in your ointment!

    Regards,

    Doc Sharptail
    "Ain't No Half Way"

    -S.R.V.

  5. #5
    Senior Member SeanMP's Avatar
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    Ditto everything Bob said with one addition. I'd like to finally get a repeater breech out there for the QB platforms as well and I think it can be done using the one design as a "universal" platform.

    Hehe...I think I just heard the sound of big steam gears grinding away over in Coalmont....
    is that possible?
    Regarding smooth twist I'm also just not sold on the idea.

    First and simplest reason is the physics tells me that the the transition from smooth to twist is an inelastic collision. with the pellet being at the losing end of the equation as far a deformation. The real world observation supports this. The initial twist is 16 to 18 and the outcome 160 that says only a tiny amount of the collision energy became rotation and the remainder deformed the mass.

    Also they are not taking the world of "one hole wonders" by storm as they said they were going to. In fact performance is closer to "also ran"

    My take is it's just simply cheaper and easier to produce.
    Sean

  6. #6
    Moderator rsterne's Avatar
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    My take is it's just simply cheaper and easier to produce.
    I agree 100%.... adequate accuracy (with skirted pellets) with only having to squash the end of the barrel onto a mandrel.... The pity is, that if it's cheaper to produce why aren't the barrels $25 ???

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

  7. #7
    Senior Member SeanMP's Avatar
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    Lotsa hype and smart marketing
    Sean

  8. #8
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    Thanks for responding guys.

    Les

  9. #9
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    Well Well Well will I get a new barrel and probe for QBob? readdy to instal been looking for one since I sold the .25cal
    Benjamin Discovery Mac1 modded <----- Ya Baby the new toy
    Webly Alecto .177
    QB79- with lots and lots of mods HPA <------ Go too AirGun for FT

  10. #10
    Moderator rsterne's Avatar
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    I knew you'd regret taking that .25 cal Cannon apart and selling the barrel....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

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