I noticed a WTT listing that noted a shooter wanting to trade "thick skirt" 18.13 JSB's (which shoot poorly for him) for "thin skirt" 18.13 JSB's (which shoot well for him). Are such pellets marked differently by JSB? I wonder if others have had a similar or opposite result from that shooter? What could the mechanism behind this be?
Thick vs. thin skirt 18.13 JSB's
- Thread starter bandg
- Start date
In all likelihood, it has more to do with the specific batch than it does the skirts in particular. It's tempting to look at the "good" pellets and compare them to the "bad" pellets and ascribe the fault to the most obvious thing that pops out. It's the old correlation doesn't equal causation dilemma.
I used to look for the same correlation with head sizes. It just so happens the 18.13gr JSBs are the pellets I've used more than any other, and my very first PCP produced amazing groups with some that measured 5.52mm. When I ordered some more, they also measured 5.52mm but they didn't group well. The very same rifle today is grouping just as well with some that measure 5.47mm (in case you're wondering, the barrel isn't choked).
The same can be said of thick skirts and thin skirts. Some batches with thin skirts have grouped well, others terribly. Some batches with thick skirts have grouped well, others terribly.
I've had all kinds. The ones that are terrible in rifle A may produce amazing results in rifle B or rifle C.
As good as JSB is, they don't seem too concerned with making a consistent carbon copy of a reference design. I frankly don't understand their strategy unless it's to produce just enough slight variations that it gives us an opportunity to find a batch that works well for the many different barrels that are out there. But whatever it is, it works.
I used to look for the same correlation with head sizes. It just so happens the 18.13gr JSBs are the pellets I've used more than any other, and my very first PCP produced amazing groups with some that measured 5.52mm. When I ordered some more, they also measured 5.52mm but they didn't group well. The very same rifle today is grouping just as well with some that measure 5.47mm (in case you're wondering, the barrel isn't choked).
The same can be said of thick skirts and thin skirts. Some batches with thin skirts have grouped well, others terribly. Some batches with thick skirts have grouped well, others terribly.
I've had all kinds. The ones that are terrible in rifle A may produce amazing results in rifle B or rifle C.
As good as JSB is, they don't seem too concerned with making a consistent carbon copy of a reference design. I frankly don't understand their strategy unless it's to produce just enough slight variations that it gives us an opportunity to find a batch that works well for the many different barrels that are out there. But whatever it is, it works.
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I've noticed the variations in the JSB 18.13". The most obvious difference is the "flat spot" inside the skirt. They both seem to shoot the same for me, and at least the ones I've checked they all weigh close to 18.13. It's not scientific, but in addition to my Impact X I have a break barrel in .22, and by pushing them in by hand they both seem to have similar head diameters. I've found this a better test than using a micrometer, at least for a rough check, as you can feel the difference especially if different brand pellets have the same diameter but different hardness. It's more of a comparison but it works for me.
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I’ve shot both and they’re equally accurate. The only difference I’ve seen is a slight change in poi. I separate the two batches and just re-zero when changing over.
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I've found the skirt uniformity has the largest impaction on accuracy, followed by sizing that fits the barrel. Would dearly like to obtain a Beeman Pellet sizer and skirt uniformer.
If the skirt deforms too easily then accuracy will go off, as the standard pellet requires the stability provided by the vortex effect of the hollow in the base. Clip a piece out of a shuttle cock and see how it flies.
I'm yet to see anything that specifies the internal barrel dimensions of FX Impact barrels. If anyone knows let me know.
If the skirt deforms too easily then accuracy will go off, as the standard pellet requires the stability provided by the vortex effect of the hollow in the base. Clip a piece out of a shuttle cock and see how it flies.
I'm yet to see anything that specifies the internal barrel dimensions of FX Impact barrels. If anyone knows let me know.
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A pellet skirt is designed to obturate at the instant the pressure pulse hits it, which conforms it to the barrel. Within reason, a thicker or thinner skirt will not meaningfully affect the ability to do that.
Time and again, people have replicated the experiment where you take pellets with slightly deformed skirts and shoot groups with them, and the results are indistinguishable from those with ostensibly perfect skirts.
The same can be demonstrated with taking more badly deformed skirts and crudely reshaping them round with a phono plug.
Just one such example:
https://www.airgunnation.com/topic/the-bent-skirt-experiment/
Time and again, people have replicated the experiment where you take pellets with slightly deformed skirts and shoot groups with them, and the results are indistinguishable from those with ostensibly perfect skirts.
The same can be demonstrated with taking more badly deformed skirts and crudely reshaping them round with a phono plug.
Just one such example:
https://www.airgunnation.com/topic/the-bent-skirt-experiment/
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I find the skirts that are thin do better shot from a gun
that is regulated and not producing a lot of power , the pellets
that have the thicker skirts always shoot better form the more
powerful airguns and if your shooting a very strong shooting
airgun buy the Air Arms pellets they like the power and I believe
that there made with a little harder lead .
that is regulated and not producing a lot of power , the pellets
that have the thicker skirts always shoot better form the more
powerful airguns and if your shooting a very strong shooting
airgun buy the Air Arms pellets they like the power and I believe
that there made with a little harder lead .
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I don't have experience with a lot of the AA pellets but one exception to this is the 7.33 AA Falcons. Several of my guns shoot them extremely well so I have a lot of them but the skirts are VERY thin. LIght pressure with a fingernail can completely close the skirts. Probably amazing that they can shoot as well as they do.
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Just slugged my FX impact X using a H&N Rabbit Magnum II, tested the resultant slug through the pellet gauge. Passes through 5.54 but not 5.53. Pushed the RMII halfway down the barrel, then pushed it back out the chamber as I didn’t want the choke measurement at this stage. Rifling marks are very faint, they were only discernible as rub marks. I suspect this is why the RMII shot so poorly and lead up the barrel unless lubed.
The regulator is set to 115bar, recommended by FX for.22 shooting. Actually recommended 110-120 so settled on 115. Shooting JSBs results in a rugged hole at 45m about 15mm, had a slight breeze.
RMII have a very solid skirt, shot well out of my Hatsan at full power, knocking rabbits over at 110m (range finder) with a mate spotting for me. I suspect DRIG is on the money RMII skirt doesn’t seal at 115bar, pushing them harder means they skip the rifling. If anyone has a smooth Impact .22 barrel try winding up the pressure shooting RMII to see if they group.
I’m beginning to think a smooth choked barrel is more suited to slug style pellets such as RMII. Smooth bore acts as a sizing die so they are correct for the rifling at the choke where they pickup gyro stability. Will push a RMII through the barrel next time to see if there is much difference.
The regulator is set to 115bar, recommended by FX for.22 shooting. Actually recommended 110-120 so settled on 115. Shooting JSBs results in a rugged hole at 45m about 15mm, had a slight breeze.
RMII have a very solid skirt, shot well out of my Hatsan at full power, knocking rabbits over at 110m (range finder) with a mate spotting for me. I suspect DRIG is on the money RMII skirt doesn’t seal at 115bar, pushing them harder means they skip the rifling. If anyone has a smooth Impact .22 barrel try winding up the pressure shooting RMII to see if they group.
I’m beginning to think a smooth choked barrel is more suited to slug style pellets such as RMII. Smooth bore acts as a sizing die so they are correct for the rifling at the choke where they pickup gyro stability. Will push a RMII through the barrel next time to see if there is much difference.
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Hi,,I had similar observations as bandg,I thought the AA were softer,both the 18 and 16 grain. The skirts were easily deformed and therefore had more imperfect pellets than other brands or models? But they did shoot very well,My Dreamline favored the 18gr AA by the smallest margin over it's favorite tin of JSB 18.13.
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