$100 worth of JSB Knockout Slug Velocity Data

@triggertreat I can only assume the changing velocities caused this???

I don't think so. The variability is there for EVERY velocity. A tight group is just as likely to be made at 800 fps as 1025 fps. Similiarly, a large group is equally likely at each velocity. The more groups you shoot, the higher the variability you'll see. There is no way around it. I prefer to focus on the average group size at each velcity. Group size at all velocities is about 14mm (around 1/2") which seems to suggest that the slugs don't get more stable as the velocity/RPMs increase.

A little past the halfway point now. The data is now statistically accurate to about 15% error at a 90% confidence interval for each velocity between 800 and 1025. This means if the data were repeated 100 more times, we'd expect 90 of the tests to fall between 13mm and 15mm average group size.



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I have sized and powder coated slugs and tested a large variety extensively in my Veteran. I have determined that mine prefers a .2155 slug size because they slide past the choke a bit easier. The result of the .2155 size is increased velocity with the same hammer spring strength, but no noticiable accuracy difference. I've found several slugs that average between 1-2" at 100 yards in my Veteran. The JSB KO slugs are one of them. I always measure the diameters to make sure, but most slugs match the label perfectly.

I too attack my accuracy issues with the projectile. I'm finding if my gun likes the projectile that it will shoot it well at any velocity. If it doesn't like the slug, changing the velocity or even the diameter doesn't make much difference. These last two observations surprised me, but the data I collected was pretty convincing. It was suprising enough that the results might be worth revisiting to make sure they are repeatable.

I haven't found a slug that is as stable as the JSB Monster Redesigns out to 100 yards. I never size them and it makes no difference. They are the best regardless.

I'm not seeing group size differences. Over large sample sizes, the group sizes have the same average of 14mm (about 1/2 inch) ctc at 50 yards regardless of velocity. I'm thinking the slugs are equally stable at all tested velocities. The slugs and shooting conditions are about as consistent as they can get and I think any small differences would average out over the large sample size.

It is possible that the twist rate of my gun is too slow to spin the slugs fast enough for optimum stabilization even when approaching the speed of sound. However, I'm leaning towards concluding that a slug that is fired at a stable spin rate does not get more stable at faster velocities. 

I don't think the data is showing any harmonic variation. The differences so far from 800 fps to 1000 fps are +/- 1mm which is well within the range of error. I'm leaning toward the conclusion that velocity differences matter much less than common knowledge suggests. Basically, my results here and with many other pellets and slugs I haven't posted yet suggest that projectiles are stable at a large range of velocities. This stability makes subtle changes in velocity irrelevant. A slug stable at 800 fps is likely to be stable at 1000 fps and equally accurate at any velocity in between. It isn't until approaching the speed of sound and the transonic zone that projectile stability is significantly affected to be noticed in group sizes.

I'm thinking the illusion of a magic velocity is caused by data samples that are too small.