Before trying the 4.52mm 8.4gr Air Arma domes I bought several tins of supposedly 4.52mm 8.4 grain JSB Exacts and found the head sizes to be "all over the place". I also bought a tin of 4.50mm labeled JSB Exacts and compared the two tins. There were Exacts from the supposedly 4.52mm tins that had head sizes smaller than those from the 4.50mm tin and visa versa. I always found that the supposedly 4.52mm Exacts were "loose fitters" in the leade of my .177 R9 however this was driven home by a THAGC field target match a few years ago. During the match I had a "dry fire" and was annoyed at myself for neglecting to load a pellet for the shot. Well, later in the match I had ANOTHER dryfire and was very annoyed at my absentmindedness to "forget" loading a pellet the second time. As the match continued I reloaded another supposedly 4.52mm Exact but when I was relatching the barrel I SAW the JSB flip out of the leade before "latch-up". LOL...I wasn't previously forgetting to insert pellets, the "loosies" were flipping out of the leade before the actual "latch-up"!.That fiasco prompted me to actually check the pellet head sizes of the remaining 9 tins of supposedly 4.52mm Exacts. Here are the results..........JSB Exacts:AA Domes:I ended up selling those tins of Exacts "fer cheap" however later I tried some 4.52mm 8.4 grain Air Arms domes and found that even though they were produced in the same JSB plant (rumor claim using Air Arms supplied dies) and found that for whatever reason the AA dome head sizes were more consistent and closer to the advertised 4.52mm...........Measuring pellet heads really isn't an "exact science" as pertaining to the "1/100th of mm" but I've developed a "satisfactory for my purposes" method that at least gives consistent accuracy based on the actual caliper reading. I'm not very concerned with the exact "third metric place reading", just that all pellets start with a consistent head size. 1st I needed a digital caliper with pretty good resolution and testing the accuracy with a micrometer test bar.......... As a side note......... I tried to use my 4.48mm pellet sizer to sort out the supposed 4.52mm JSB Exacts and found that a HIGH percentage of the pellets dropped through the die without any sizing. I did the same with my stash of 4.52mm Air Arms domes and almost all were sized to 4.50mm! I also found that H&N FTTs had larger heads that fit snugly in my leade without sizing which is probably the reason they were accurate without "molestation" however I still sized them because it only takes about 5 seconds to size via the "homemade pellet sizer" plus each sized pellet is guaranteed to be as round as the die itself.......
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