How old are your JSBs 18gr? I measured some bought a few months back and there all right around 5.5mm and some AA 16gr are 5.51mm and the redesigned monsters are 5.53mm
Shoot a bunch of pellets and don't clean the barrel. Those pellets will be sized just right in time. However, the opposite can happen too with new pellet arrivals being too large in diameter. Just depends on the barrel and how picky it is. I would think that the Speed without a choke (I'm thinking) could be a little picky.
Quote from: triggertreat on December 13, 2018, 04:22:45 PMShoot a bunch of pellets and don't clean the barrel. Those pellets will be sized just right in time. However, the opposite can happen too with new pellet arrivals being too large in diameter. Just depends on the barrel and how picky it is. I would think that the Speed without a choke (I'm thinking) could be a little picky.Te Air Speed has a choked barrel, at least the .22 does, can't really speak to the others, but I thought I read they all (.177, .22 & .25) had choked barrels. The exception is the .30 cal that's coming, it's supposed to have an un-choked barrel..
Paul, I remember Scott (motorhead) saying he ran into undersized 18s back some months ago, perhaps as far back as a year ago. I still had some stock so I had not seen it myself. Hopefully he will see this thread and comment on the specifics. I’ll check tonight and see what my most recent tin measures, although I expect they were bought a year ago. I know I have some from either 2015 or 2016 that measure 5.48mm and they are wickedly accurate from the B50 with its factory unchoked barrel. Good enough that a complete novice was quickly smashing 1/2in Mardi Gras beads with them at 43 yards a few weeks ago. I have measured and logged a good variety of pellets over the last 5 years or so and I’ve only encountered a few examples that were down around 5.42mm. One was from a batch of RWS Super H-points from the middle of the year and another was some Gamo wadcutters that belonged in the hall of shame. I’ve never seen them that small from JSB or H&N, and just the occasional peewee outlier from a tin of Crosmans. To be honest, the fact you’re seeing undersized pellets across the board makes me think the calipers are off, perhaps the heads are getting compressed, or canted, or something along those lines. If you want to check the calipers, take a 1/4in drill bit and measure the smooth portion of the shank (an area undamaged by the chuck). The calipers should indicate 0.249in plus or minus a half thousandth, even with budget bits from Walmart or Harbor Freight.
Pellets, of course! This is an air gun forum!I had an interesting chat over FB Messenger this morning with someone from Evanix. During the conversation I had mentioned that I had sent the barrel from my Evanix Air Speed to Travis at JSAR to inspect due to some issues with accuracy. They asked what pellet I was using and I told them the JSB 18.13 grain. They mentioned how that were having issues with these pellets and recommended the H&N Baracuda.According to the person I was chatting with, the issue was the diameter of the head of the pellet. They sent a picture of a pellet (that I assume is a JSB 18.13 grain) that showed the head size was 5.42mm, not 5.5mm. This prompted me to go measure the heads on some of the JSB 18.13 grain pellets I had been using. Sure enough, the size of the head was 5.42mm. They said the old JSB 18.13 pellets were 5.5mm, but the newer ones were not. The person I was chatting with eluded that this could be the cause of my accuracy problem, but these same pellets shoot really tight groups from my Mrod and BullBoss! Anyway, this got me to thinking about other pellets, so, being the curious one that I am, I started measuring the heads on all the pellets I have on hand. I'm here to tell you, I could not find a single pellet that had a head that measured 5.5mm! I measured some JSB Monsters, H&N Barracuda Match, H&N Barracuda Hunter, CPUMs and Air Arms something to others and every last one of them measured between 5.41mm and 5.46mm! Unfortunately, when you place an order for 5.5mm pellets, you really have no way of knowing what exactly you are going to get.Are there any pellets that actually have a head that measures 5.5mm? Are these shrinking heads an industry epidemic?
That is an interesting article and they were all less than 4.5mm, which makes me wonder if having a head size less that 5.5mm for a .22 is as critical as the folks at Evanix made it seem. Granted 5.42mm is on the small side and having heads there are 5.46mm or larger would be better, but I'm not so sure they really need to be 5.5mm or larger.Here are some pictures of a JSB 18.13 pellet from the same batch that I pushed through the barrel of my Air Speed. What I found interesting was the rifling when all the way around the head, but only half was around the skirt. Also, the skirts measured 5.46mm so they were slightly larger than the head of the pellet.