ScopesAndAmmo.com Store Logo

+ Reply to Thread
Results 1 to 8 of 8

Thread: 9mm/.357 JSB Exacts and Upsizing the .30 Cal

  1. #1
    Moderator rsterne's Avatar
    Join Date
    Wed Dec 7 2011
    Location
    Coalmont, BC
    Posts
    1,266

    9mm/.357 JSB Exacts and Upsizing the .30 Cal

    I received my .35 cal JSB pellets from AirGunSource today.... and while the .30 cal are too small for a Lothar Walther barrel, these appear to be PERFECT....



    The head measures 0.357", the skirt 0.366", and they are 0.423" long.... I weighed out 10 at 776 grains, so they avergage 77.6 gr. virtually exactly what it says on the tin.... They are covered with a black substance, possibly graphite, which rubs off on your fingers, making them a bit messy to handle.... but they are typical JSB quality.... I pushed one through my LW barrel, and once the skirt is fully engaged in the rifling, it slides through with just a nice resistance.... Upon examining the pellet (lower one in the pic), the head has some very slight scuff marks between the rifling grooves, indicating it is barely rubbing on the groove diameter of the barrel, with the rifling fully engaged.... The skirt was slightly collapsed from being pushed through with a rod (which pushes on the middle only), just as you would find with any pellet when pushed by hand.... IMO, they are a perfect fit in a 9mm (0.357") LW barrel.... I can't wait to test them when I get the .357 barrel on my Hayabusa....

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

  2. #2
    Senior Member SeanMP's Avatar
    Join Date
    Thu Dec 22 2011
    Location
    Just south of "Out There"
    Posts
    911
    Those look really great Bob. Where did you get them?
    Sean

  3. #3
    Moderator rsterne's Avatar
    Join Date
    Wed Dec 7 2011
    Location
    Coalmont, BC
    Posts
    1,266
    AirGunSource.... they also carry the .30 cal below....

    By now, most people will have heard that the JSB .30 cal pellets are a true 0.300" head diameter, and loose in a Lothar Walther barrel.... I made an upsizing die today for them to increase the head to 0.308" diameter and swell the skirt to match.... Here is the die (poor photo, sorry)



    I made a shouldered punch that can only go together a set distance.... The tapered pin the pellet sits on is 22* with a 0.120" end.... It swells the skirt to about 0.316" when the end is seated far enough to allow the head to be sized to 0.308".... The inside of the punch has a 1/2" clearance hole, and the a 5/16" guide hole to keep the pellet centered is made with a mill so that it has a flat end.... I wanted to leave a meplat on the pellet to see how it works that way.... The tapered pin is adjustable for height.... raising it increases the head diameter.... Once I had the height set, I turned off the end of the pin flush with the bottom of the die so they can sit on a steel block and it will have no tendency to move.... To use it, you balance a pellet on the tapered pin, slide the punch over the top and into the hole, where it stops, resting on the pellet, about 1/16" above the shoulder.... A couple of taps with a hammer upsized the pellet.... You remove the top punch, and pull off the pellet.... Here are the pellets, one is sitting on the pin in the die....



    On the bottom right is a stock pellet that was pushed through my Lothar Walther barrel.... there are virtually no rifling marks on the head, and only light ones on the skirt.... To the left of it is one of the upsized pellets pushed through the same barrel.... You can see the difference, the head now lightly touches the groove diameter, and the rifling is fully engraved.... I won't know how the accuracy is until I can get outside when the weather warms up.... but I'm hoping to see a significant difference....

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

  4. #4
    Senior Member SeanMP's Avatar
    Join Date
    Thu Dec 22 2011
    Location
    Just south of "Out There"
    Posts
    911
    That's bloody ingenious.....

    I wonder what the heck the folks at JSB sized that pellet to?

    29 cal isn't exactly popular. In fact I can think of only one the 7.35-52 Carcano
    Sean

  5. #5
    Moderator rsterne's Avatar
    Join Date
    Wed Dec 7 2011
    Location
    Coalmont, BC
    Posts
    1,266
    Seems they made it on the request of FX and Daystate I guess.... bloody ridiculous IMO....

    Now on the GTA a guy that is building a .30 cal B50 says the LW barrel he just received is 0.298" land and 0.303" groove....

    WTF is going on?.... *growl*

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

  6. #6
    Senior Member SeanMP's Avatar
    Join Date
    Thu Dec 22 2011
    Location
    Just south of "Out There"
    Posts
    911
    That doesn't even sound like a 30 cal barrel
    Sean

  7. #7
    Moderator rsterne's Avatar
    Join Date
    Wed Dec 7 2011
    Location
    Coalmont, BC
    Posts
    1,266
    Tell me about it.... a pellet pushed through my LW .30 cal measures 0.3075" and the grooves are smack on 0.300".... I'm betting yours is about the same.... I sure hope LW don't change !!!

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

  8. #8
    Moderator rsterne's Avatar
    Join Date
    Wed Dec 7 2011
    Location
    Coalmont, BC
    Posts
    1,266
    I still haven't had a chance to try them outside, but I tried a comparison indoors at 7 yards between the stock pellets and the upsized ones in a .308" PB barrel on my .30 cal Disco Double prlject.... Here are the results with the stock pellets (0.300" head size) on the left and the ones I upsized to 0.308" head size on the right....



    The C-T-C groups size on these 5 shot groups went from 0.3" stock to 0.1" with the proper head size for the bore.... I would be surprised if results outside are any different.... I know that Voltar1 found a huge difference in a 0.308" barrel with the pellets he swaged larger as well.... Incidently, I can upsize a tin of 150 in 15 minutes....

    BTW, the latest word on the oddball LW barrel that the guy on the GTA has is that the groove diameter is 0.305" "or maybe a bit more".... I saw a pellet he fired through it at near valve lock (ie low velocity) and it did have deeper rifling marks than a stock JSB pushed though my LW barrel.... so I can believe it may be about 0.305"....

    I'm encouraged by the way the upsized JSBs shoot in the PB barrel.... It bodes well for how the stock pellets will work in our new 0.300" barrel....

    Bob
    Last edited by rsterne; May 24 2013 at 12:41 PM.
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

+ Reply to Thread

Similar Threads

  1. 9mm/.35 cal JSB Exacts Coming
    By rsterne in forum General Airgun Questions
    Replies: 3
    Last Post: Mar 28 2012, 07:15 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts