Things I liked:Made of lead. Useful for maximizing the weight of my son's pinewood derby car. Things I would have changed:I couldn't figure out why they were shooting so poorly until I measured them. Head diameter variation was a staggering 0.23mm! Typical head sizes were only 5.46mm, with a high of 5.59mm and a low of 5.36mm. To give it an approximate timeframe, my tins were purchased in December 2012. Brandishing them as "Match" pellets is borderline false advertising at worst and disingenuous at best. What others should know:Quality control with Gamo's pellets seems very hit or miss recently. We had good luck with the Gamo Rockets in .177 cal in my son's rifle. The heads are a consistent diameter. Also have read good things about the Red Fire pellets.
Things I liked:These pellets breathed new life into a cheap Beeman RS2 dual-caliber rifle that had been sitting in the closet for 6 months. The rifle is stock except for truing up and polishing the crown of the .177 barrel. With the JSB 10.3gr pellets, it is giving me 0.5" 5-shot groups at 25 yards consistently and an occasional freak group of 0.2" to 0.3". Groups at 42 yards are .6" to 0.75".
They fit the breech loosely and I've come to expect poor accuracy when that is the case but not so this time. Measuring the heads of 20 samples from a tin purchased June 2013 produced:
0.0004" std dev
I don't have super-precise measurement capabilities but checking with precision gauge pins gives me confidence to interpolate to one-half thousandth (0.0005"). Things I would have changed:Nothing. What others should know:Pellets of this weight may shorten the spring life for many springers. Generally speaking, I would consider these suitable for a MSP or PCP rifles only. If you have access to a chronograph, check that energy (fpe) isn't falling off compared to typical 7 or 8gr pellets. If you get less with a heavier pellet, it is a sign the powerplant (spring) is not working optimally and may shorten its life somewhat.
In the case of my Beeman RS2, Crosman Premier Ultra Magnums of a similar weight (10.5gr) produce less power than 7-8gr pellets. But the 10.3gr JSBs produce more. The CPUMs fit very tightly to the barrel versus loosely for the JSBs so I suspect friction is playing a big role.
Things I liked:Consistent head sizes. Getting 0.2" - 0.35" groups at 25 yards with a QB79 HPA conversion. Repeatable, not freak occasional groups. My 7yr old boy is hitting 0.4" diameter Mardis Gras beads pretty consistently at that distance (roughly 75% of the time). He can't wait for squirrel season to begin!
They also shoot well in my Beeman RS2 springer, yielding 0.4" - 0.5" groups at 25 yards. Occasionally better, occasionally worse depending on how well I'm on my game with a consistent hold on that particular day. Things I would have changed:Nothing. What others should know:Great alternative to the similar JSB 10.3gr. Some will say they are identical but there are in fact subtle differences such as the dome profile, overall length, and skirts. In our two rifles both brands group similarly well, with a slight edge going to the Air Arms. The fact they cost less is a bonus.
Measured head sizes indicate good consistency, though are somewhat smaller than the claimed 4.52mm.