Early results for NSA 12.5 grain slugs

[Mole2017]

Well, I finally got a chance to get out both chronographs and do some back to back testing of the new 12.5 grain .177 slugs from NSA. In short, my routine is to set up one chronograph at 30 yards and another on the muzzle of my R10 and fire away. So long as I remember to reset the CB-625 and I get a decent reading off either of them, it is as easy as 5 to 10 shots each and some messing around with software afterwards.

I did happen to do a back to back "calibration" test where I took a shot over the one chrony a point-blank range so I had the speed as it comes out of the CB-625. That showed that my two chronographs differ by 3 percent. I suspect it is the CB-625, which was shot accidentally a while ago and was saved, but one sensor was affected. Fortunately, that has a built in feature to tweak the calibration to bring it into line, if I assume it is the one that is in error.

Adjusting for calibration differences, I am happy to report that the BC for these NSA slugs is 0.056. I don't use that so much as I just shoot them and note what I need to know for hunting with them, but there it is. By way of comparison, it is interesting to note the average data of 6 to 10 shots each (corrected for that 3% difference):
                     Muzzle                       30 yard
JSB 10.34      903 FPS, 18.7 ft-lbs     747 FPS, 12.8 ft-lbs
NSA 12.5       806 FPS, 18.0 ft-lbs     754 FPS, 15.8 ft-lbs

What I saw right off was that though launching ~100 FPS slower at the muzzle, the BC is so high that the NSA is going faster than the JSB at 30 yards. The first shot for each string was higher than the average, but only by 1.5%or 1.7% (JSB was worse and the first up for the testing today). Most of the shots were within 0.5% of average, which is encouraging.

The other comparison I do is look at the energy lost over the range. The JSB pellets lost 32% of their energy; the NSA lost only 12%. In fact, at 75 yards (according to the software), these are still carrying as much energy as the JSB had at 30 yards. Playing with the software some more, the trajectories differ the most at 50 yards, the NSA dropping about 0.6" more, but by 75 yards they are right on top of each other again as the JSB starts dropping faster, having slowed so much more than the NSA. I had already noticed I didn't need to adjust by much at 30 yards, so that is encouraging. Before packing up today, I happened to take some shots at a dirt pile that was 50 yards away and noted the drop was only 1 mildot at 12x on the scope. Last I checked, the JSB had been 1/2 mildot or so at 16x, but that was a different scope too.

So far the R10 is liking them, though they are a little fussy in the magazine, wanting to fall out of the front just as easily as the back until I get it into the rifle. Of course, the real test will be in the field. Today I'm looking forward to testing them out at further ranges and am hoping to get some woodchucks before the kudzu dies and they start getting scarce. I'll see if I can remember to shoot some paper too.