9mm/.357 JSB Exacts & Upsizing the .30 cals to .308

[rsterne]

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

[Monkeydad1969]

Time to go hawg hunting Bob.  Nice going.  Can't wait to see the finished work.

Joe

[Nomadic Pirate]

have some preordered for my Rainstorm .357

[rsterne]

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

[Bruce]

Bob,

That is brilliant! Next your going to have a side business making the pellet up sizers

Bruce

[PakProtector]

Bob,

That is brilliant! Next your going to have a side business making the pellet up sizers

Bruce

that or a side occupation saying, 'NO'...lol
cheers,
Douglas

[rsterne]

or a side occupation saying, 'NO'

You got it!.... not enough time for my own projects.... and NOW I have to size my own pellets?..... UGH !!!

Bob

[badredbird]

only you bob   you never cease to amaze me  im going to look into the jsb  357 pellets

[rsterne]

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....

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

[Bruce]

Awesome Bob!

Thanks for the follow up!

Bruce

[PakProtector]

Bob, I have got to make one of those to deal with 22 cal pellets. I need 5.52-5.525 head size and the JSB heavies seem to be about .01 mm undersize. The 5.53 'cudas shoot well at close range, but don't keep it together like the JSB of proper size do at long range( 3" group at 170 yards v. 10-12" for the 'cudas ). Wid one of those I can afford to ignore JSB variability from tin to tin...lol
cheers,
Douglas

[rsterne]

Well, maybe!.... The way mine works, if the overall length of the pellet varied it would probably size to a slightly different diameter.... If you want an absolutely acccurate finished diameter, you would have to have the head of the pellet fit inside the (accurately sized) die, which would in turn cause it to stick and have to be pushed out.... All my die does is support the inside of the skirt and smack the nose which shortens the overall length and increases both the head and skirt diameters because the lead has to go somewhere.... It took a lot of playing around with the taper of the back pin, the diameter of the front of it, and the distance between the pin and the front of the die (the pin threaded in and is therefore adjustable) to get the ratio of head expansion to skirt expansion just right, ie 0.008" on both ends....

Bob

[PakProtector]

Well, maybe!.... The way mine works, if the overall length of the pellet varied it would probably size to a slightly different diameter.... If you want an absolutely acccurate finished diameter, you would have to have the head of the pellet fit inside the (accurately sized) die, which would in turn cause it to stick and have to be pushed out.... All my die does is support the inside of the skirt and smack the nose which shortens the overall length and increases both the head and skirt diameters because the lead has to go somewhere.... It took a lot of playing around with the taper of the back pin, the diameter of the front of it, and the distance between the pin and the front of the die (the pin threaded in and is therefore adjustable) to get the ratio of head expansion to skirt expansion just right, ie 0.008" on both ends....

Bob

I suspected there were a few tried at the skirt punch. What relationship is there to the angle on the inside of the skirt? I suspect I will just have to do a wee bit of experiments to make one close enough. I figure if the head goes up a thou, if the tail is going anywhere bewteen half and double I will be OK...it is not nearly such a large diameter I wish to change.
cheers,
Douglas

[rsterne]

The length between the end of the skirt punch and the front of the die (that strikes the pellet, squashing the head and causing the meplat) mostly governs the diameter of the head.... The top end of the skirt punch should be about the same size as the inside end of the skirt (I think mine is a whisker bigger to insure centering), or it will swell the waist.... The taper of the skirt punch mostly governs how much the skirt expands.... The wider the base of the taper the larger the skirt becomes.... My punch expands both the same amount, 0.008"....

I threaded the OD of the skirt punch and the ID of the base section so I could vary the height, and hence the head diameter.... Once I got the right height, if the skirt was too small, I pulled the punch out and widened the taper.... If the skirt was too big, I narrowed the taper.... Once I found the perfect combination, I loctited in the punch and turned the base of the assembly off flat so the bottom of the punch was flush with the bottom of the base and there was no load on the threads, they both sat on the anvil I use when swaging.... It takes two light taps of a relatively small hammer, and I turn the top about 90* between strikes.... The first strike probably does all the work but it sounds "dead" because the lead cushions the blow.... The second strike "rings" indicating the die is bottomed steel to steel....

It probably won't matter if you expand the skirt of your pellet at all, as they will already be well over bore size.... In your case, I would try and match the shape of the punch to the inside of the skirt, and adjust the clearance to get the head expansion you need....

Bob