Thoughts on sorting JSB MKI's

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My brother shoots small bore competition and he weighs and sizes his bullets. I don't think this is just a JSB issue. I had heard from long-time airgun shooters that JSB use to be more consistent however, I believe top shooters back then were weighing and saying the same thing. I don't know the process of making pellets but I image it would be tough for JSB to sell a tin of pellets for $100 if it was a lot more effort. If they could offer a smaller variance in size and weight, I believe many (but not all) would be willing to pay 30% more. I am very interested as to the results Matt Dubber and FX come up with. We may be seeing air rifles switching to bullets to take accuracy to the next level for air rifles.
 
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I receive my Pellet Gage a couple of days ago. It looks like 80% of my MKI's are what I'm calling 6.38mm. The other 20% were 6.37's and 6.39's split about even. That's the smallest size (6.38) that the pellet will just slip through the hole. I guess I could call them 6.37's but decided to go with the "go" hole. Seems do be a very good tool but a slow process that can eat up some time.

As mentioned before I like to size my skirts to .252" regardless and it seems to help a little in my Royale and RAW, have seen no detrimental effect what so ever. Now I'm wondering if after weighing, size the skirt like I normally would do and give it a long arching Yrrah roll. My thinking is that since the skirts are all one size now to a 100/1000th, rolling and observing the arch should determine the head size as well. Should be a good test for the weekend and I don't think it'll take any longer that using the pellet gage.
jk
 
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Well to be honest this test was kind of inconclusive. As mentioned I did size some of my recent 33.6-33.9gr weight sorted heavies that I had previously head gauged with the Pellet gage. I then rolled these across a 12-13" span of glass. The tendency was that the smaller heads (6.37) made more of an arch and the larger ones 6.39 a flatter arch which made sense. After rolling about 150 pellets and resorting as rolled groups into three groups, A,B and C, the number counts were basically the same as the Pellet Gage count's. With the largest group being B which was the same as the large group of 6.38 head sized.

After sorting into three groups I went back and check the head sizes on a few. What I found was that not all pellets in A that should be 6.39's actually measure 6.39. Some were a little smaller. The majority were like they should be. The same held true for the other groups as well. But............ I also noticed that the Pellet Gage that it's not a definite GO,NO GO either. It depends on how lightly you set the pellet into the hole and how straight it is. You can also turn the pellet and set it back into a hole and it might either fall through or not.

I guess either way is not 100% precise but I'm leaning toward the sized skirt/rolling test as a little more accurate as I re-rolled several across the 13" of glass and they would end up almost exactly at the same spot every time. The Pellet Gages repeatability was not as conclusive. 
Jimmy 
 
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Just thought I would note my conclusion from another post and add that weight sorting seems only to be justified fo getting rid of bastards.

Well in summary, it looks like my gun (2013 Matador R3M .25 long) prefers the larger head diameter. This surprised me, testing the JSB MKII Heavies (Deep Skirt) or the similar Edgun 34g. The following results entailed (6) 5 shot groups @ 50 yds, of each specified head diameter. This testing was very comprehensive, as 1500 pellets were cleaned, inspected and sorted for weight and head diameter. Roll sorting was discontinued (for skirt diameter consistency), when it became evident that this was a waste of time, as they were all very consistent. Groups were shot alternating through each head size, to maximize a comparable environment…there was changing wind so comparative accuracy, rather than absolute accuracy, was the goal. Here’s what I came up with:
6.37mm- .99″ ctc
6.38mm- .96″ ctc
6.39mm- .75″ ctc
6.40mm- .63″ ctc
6.41mm- .58″ ctc
Unsorted- .76″ ctc
Note that “unsorted” pellets came in, where expected and the accuracy trend lends itself to validate this test. Also noted was, the Edgun 34g were more consistent in head diameter averaging midrange diameter. My overall conclusion is that sorting helps a little bit but is probably not justified. I see more accuracy gains in finding the pellet lot that works best for my gun…in this case the old MKIIs with the shallow skirt. On a side note, I tried lubing some unsorted pellets, that had been cleaned and tested them against non-lubed, in no wind conditions. The accuracy gain was insignificant with results being .56 ctc vs .58 ctc, respectively. The big surprise was the gun seemed to digest the larger head diameter better than the smaller diameter…I would have expected the opposite. Here’s an example of on card w/ the 5 head sizes represented:
 
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"jking"What did you use to measure the head size? If the Pellet Gage, that's a lot of time involved for 1500 pellets. Yikes! Also,my MKI's seem to be pretty consistent as far as head size. The majority I called 6.38, just because that was the hole they slipped through first. I didn't find any .36's and only a very few .39's.
JK

​Ya, about 3 full length movies. You are correct sir...used the Pellet gauge w/ 3 tins (+) of Edgun 34g pellets and had similar results. About half 6.37 and half 6.38 using the same "fall thru" method. There was maybe 30 outside this on either end. The remainder sized, were newer MK IIs which had more variation from 6.36 to 641. Both pellets being so similar, I have concluded that consistency is simply hit or miss, depending on what lot you end up with.

​PS: Got my first air rifle opportunity @ a coyote, 3 days ago, while hunting rabbits. He was standing below the horizon @ 145 yds so I obviously tried for the head shot and shanked it...can you say buck...scratch that...dog fever?

Click to expand...
 
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After sorting by weight and then moving onto head sizing and experimenting with the different options available there. I have come to the conclusion and have the most confidence that I find sizing thejust the skirt down to .252", the largest size I have ( I think that even a larger size would work great too as long as it sizes the skirt) and then doing the roll method across the glass determines head size better than the pellet gauge. The reason I say this is that as mentioned above I got varying results with the Pellet Gage. Sometimes you can make the same pellet "not fall through" from 6.37 to 6.39. More often than that, it could be called a .37 or .38 or .38 and .39. I figured once you size the skirt to an "exact" size of .252 and giving it a long roll across glass the repeatability of where that pellet lands on the far side is almost 100%. Also after sorting some this way they tend to also be as consistent as you can expect with the PG. I mean the more arching being in the 6.37 range of the gage and the less arching leaning toward the 6.39 range, again with non confident results. This is just my thoughts though. It's always seemed to work well in my guns. Here's a photo of one of the pellets with just the skirt sized.
JK
afa435e8e6c31ca3230ff31428823b65.jpg
 
 
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I use these NOE pellet sizing dies. I have .249 thru .252. I've only used the .252 to size the skirts a little. I think just getting them perfectly round going into the breach helps a little. Even a .253 would work ok, just happen the .252 is the largest one I have. I haven't tried sizing the heads since that would really take the skirt size down, probably too much.
Jimmy

c37d3c5dd5f5b3df79b26acd7dadb13e.jpg
 
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Your probably correct agnthooziast on the T R Robb rig. , The NOE's sizing die is tapered and I don't see anyway to use them for just head sizing. The smallest ID is just as it exits the bushing.
JPS, this is the first time in a looooong time that I washed pellets and this applied lube. All this time on the 25 cal pellets I've been relying on the lube or process film as my lube and just sizing etc. This time I went full bore, washed, sized and rolled then used Tom's method to lube with FP10. Shot my Royale and Wildcat this afternoon and they were grouping really well. May continue this for a while with both of these guns and see how it goes.
JK
 
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I'm assuming that when you say grouping really well that you saw a measurable enough improvement to continue that method. I hope it works. I'm looking forward to experimenting to find out what works when I get my crown. Thank you for your knowledge and sharing with us Jim. Tom is a sharp guy and experienced like yourself and sharing that knowledge and experience is key for us rookies in the pcp world. Hitting a squirrel at 35 yards is a big deal for me with my old springer! bill
 
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