Have now loaded 300 HBN coated 145 Matchburner bullets. Here are the good and the bad things that i have observed:
1) Pressure and speed is reduced significantly compared to naked bullets if powder charge is kept the same. Speed goes down from 2750 to 2695, so by about 55 fps. Way outside the node, and you really have to add more powder to stay inside the node.
2) Need to load about 0.6 gn more H4350 to get back to 2750 fps. Once back at the prior speed, group size is about the same as before. I could not see an improvement in group size. Neither did it get any worse. In this scenario, brass will last significantly longer, and this is a useful cost saving. You will spend slightly more on powder, but this is insignificant.
3) Once back at the prior speed, pressure is clearly lower, primers are less flat, and the cases have soot down to the shoulder-body junction:
This is usually what you see with a starting load from the load manual. Primer radius is also more pronounced.
4) At the prior speed (and lower pressure), the carbon on the neck and shoulder is inconsistent, looks like inconsistent combustion. Some stop at the neck-shoulder junction, some go way down on the shoulder:
Is this a problem, SD was 7.3 fps for the 15 rounds i recorded before the Labradar battery died. Surprisingly good. One outlier (very sooty case) that was 15 fps lower than average, the rest were all very close (SD ends up at 5.7 fps if i delete the ‘outlier’).
5) If i load higher, the soot pattern on the case goes back to normal, and a sine wave pattern appears on the neck. Shoots just as well at this “higher node”. Might end up as a compressed load, and then you need to settle the powder before seating the bullets. That adds one more reloading step.
6) Clearly less copper fouling than before. I now clean about every 150-200 rounds now. It is mostly carbon that comes out. Takes very few rounds (2-5) to get the cleaned barrel back to normal/prior speed.
7) Bullets coated in different batches come out looking a little different. Loaded a batch of 100 that came from two different tumbling sessions, and they looked different, SD went up from 7-8 range (prior batch) to 14 fps. Seems one group of bullets was 15 - 18 fps slower than the other. I think this is enough to drop out of the node.
8) If you forget to take bullets out of the plastic bottle, then after a few days the bullets show some green/black corrosion. Bad idea!
I think HBN works well enough and is simple enough to apply.
You can load higher, but load manuals become fairly useless. Sufficient care and attention is required, and if you don’t know how to read pressure signs, you really should avoid HBN until you have gained much more experience. Not for beginners.
It is not a fix for all problems, but if you are chasing a higher node and hitting pressure problems, it can be useful.
Cold bore shot at 600 feels like it is a little better than before, but it is too early to tell. Have checked it 6x now, and speed for the cold bore shot is often within 10-15 of the average. It was worse before, usually 15-25 fps lower.
