HBN, Poly twist and off the charts loads

Rock Knocker

Active member
I just ordered enough hexagonal boron nitride to coat a couple years worth of bullets. I have been thinking of trying it for a bit and I finally made the cheap purchase.

I'm most interested in what's going to happen with my BHW barrel, the polygonal twist already keeps pressures low and HBN is going to drop it a bit more.

I've done a bit of looking around to find others results with HBN and it seems to make a noticable difference with pressure, allowing more powder and ultimately more speed, not in small amounts ether. Similar to my poly twist results.

So who knows what's going to happen? I havent seen anyone shooting poly twist barrels with a lubed bore and bullets and my poly twist 223 loads are already off the charts. What kind of speed can be had? Any accuracy..? I've seen this gun hold 12+moa.

Ive got H322, Benchmark, H335, Varget, and CFE223 on hand, a bunch of Hornady 50gr SP and some TSXs. I will be picking up another box of 65 SGK to load up also.

I also will be playing around with my 260AI and 140gr VLDs with it's big 30" barrel, some online reports were showing over 150fps potential gain from HBN in 6.5 Creed 24" barrel. If I can add 100-150fps or more to a 140 VLD that will be nothing to sneeze at.

Has anyone else around here played with bullet coatings?
 
It should be fun to play with, even if I see no changes in the BHW the 30" barrel should benefit in one way or another. And for $20 even if it's a waste of time on bullets I will have years worth of dry lube for anything else.
 
I got out with my first small test batch and things seemed to do great.

In my 16" BHW barrel load development usually has groups jumping from one to three inches, or a lot worse. I just loaded up 65 SGK with HBN on top of Benchmark powder. I loaded 24.0, 24.5, 25.0, 25.3 and 25.6, none of them grouped over 1.5".

25.3 shot a .60" group and 25.6 shot .80". 25.6gr Benchmark caused light primer cratering in the CCI450s but pretty much no flattening, I could work higher if I wanted. Keep in mind, 4x scope on a carbine AR and a semi solid mud clump for a rest, these are good groups.

Even after my HBN testing I fired three extra rounds I had rolling around, 53gr TSX no HBN, even those grouped tighter than normal when fired through the HBN coated bore.
 
I threw together some more test loads today.

65gr SGK HBN, Benchmark 25.9,,,26.2,,,26.4

53gr TSX HBN, H322 26.0,,,26.3,,,26.6

Pressures were surprisingly low with most the shots. The cold bore shot was 26.0 TSX and it flattened the primer the most, a couple others flattened primers and one showed an ejector swipe. I'm thinking the random pressure spikes have to do with my brass prep, or lack thereof. I throw all my AR LC brass together and I noticed when I loaded some of these test loads some of the necks were hard, bullet was hard to seat and necks were scraping bullet copper off as I seat the bullet, and I assume scraping the lube off also causing higher pressure.

Groups opened up a bit compared to lower charges but a couple groups had two holes touching with the third shots thrown, maybe that neck hardness issue...?

Still no velocity tests, next time I go out I will anneal some brass and try to take some 100 and 300 yard shots to measure drops.
 
Higher pressure cases on the right side of the group, but higher pressure signs didnt necessarily mean the larger powder charge.

49741012652_fb3c6270bb_c.jpg
 
If you are scraping the jacket off seating bullets you need to chamfer the inside of the necks on your brass.
 
Yup, some of these cases could be shot two times and others eight times, it only happened to a few cases and the necks were deffinately harder than normal. The next ones will get a full make over, anneal, trim and chamfer.
 
Ammo shortages slowed things down but I figured I would dig this up.

I've settled on 26.9gr H322 with HBN 53gr TSX, primers are flattening a bit but these wont be plinking ammo.

Shot a 3 shot 300 yard group today, I got a 1.75 group that only dropped 4 inches from 100 yard zero. My 53gr noHBN TSX dropped 8.5 inches at 300. It seems too good to be true. I set up in my buddies yard for a quick test, I will get out for more shooting soon. I moved and need to find some news spots.
 
Someone else try this out, no fudging my 16" 223 is shooting faster than 22-250 and more accurately than before to boot.

I'm not sure if I should contact NASA about this or what, i want to see if someone else gets similar results.
 
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