As many of you know, earlier this year, JSB introduced a new .25 caliber pellet called the, "EXACT KING HEAVY." The original EXACT KING weighed in at 25.4 grains. JSB decided to kick it up a couple of notches, and introduced the EXACT KING HEAVY, at a weight of 33.95 grains.
It turned out to be a very accurate pellet, in most guns, but there was a problem with it in some magazines. The skirts were too big to allow the pellets to fit into the magazine chambers. Not on all mags, just on some. As an example, they would not fit the mags for my Kalibrgun Cricket rifle.
I got around the problem, by using the magazine as a sizing die, and pushing all of the pellets through the mag chambers, by hand, using a small brass punch. That worked out great, and the accuracy was an inch or slightly better, five shot groups at 100 yards.
As soon as they were aware of the problem, JSB set about correcting it, by developing a new version of the pellet, called the MKII, with a smaller skirt.
I recently acquired a quantity of the MKII's, and decided to see how they compared visually, dimensionally, and weight wise, to the original version.
First up was to see if there is a noticeable difference visually. I could see right off that the skirt on the MKII is thicker, at the rim, than the original, and also, that the cup in the MKII is more shallow and wider than on the original. Those differences can be seen in the photo below.
Another difference, is the overall length of the two pellets. The original version measures a very consistent .3525, and the MKII's measure a very consistent .3455, or .007 thousandths shorter than the originals.
Next up, using my Pellet Gage, I sorted a tin of 300 pellets by head size. They sorted this way, 215 had a head size of 6.37mm, and 85 had a head size of 6.38mm. When I sorted a tin of the originals, they had head sizes of 6.38mm, 6.39mm, and 6.40mm.
I took the group of 215, that sorted with a head size of 6.37mm, and sorted them by weight. The MKII's had the exact same weight spread as the originals, when I weight sorted them. The lightest were 33.8 grains, and the heaviest went 34.8 grains, with the bulk of them running between 34.1 and 34.4 grains.
Of course, what we really want to know is, do the MKII's fit in the mags, and how do they shoot. They definitely fit in the mags now. As far as how they shoot? Well, it's a bit windy up here right now, so I'll try and catch a calm day, in the next week or so, and do a side by side accuracy comparison, with the original version, and see what we get.
My understanding is, that JSB is going to produce both versions. Hopefully, the MKII's shoot as well in my gun as the originals, but if not, I'll just pick up some more of the originals and hand size them.
Until next time, thanks for reading.