Hexagonal Boron Nitride

[Pdvdh]

Chronographed some HBN coated bullets, fired from HBN coated bores, in two different rifles. I have extensive chronograph MV data from both rifles from the prior 7 years firing the identical uncoated bullets. The MV of the first bullet fired from each freshly HBN-coated bore was NOT recorded. MVs were recorded over a set of triplicate chronographs, meaning three MVs were simultaneously recorded for each bullet fired using three separate chronographs. Chronograph agreement was excellent. Confidence in these MVs is high. My current disclaimer is that I only fired one bullet at each powder charge as this was my initial testing of HBN-coated bullet MV. But I expect this data to be reinforced with additional chronograph sessions, because my findings are similar to what others have reported.

7mm Rem Mag, 168gr Berger VLD, Federal 210, Hodgdon Retumbo, bullets jammed 0.010":
Historical uncoated bullet MV=3044fps loaded with 74.6gr Retumbo.
Coated HBN bullet/bore MV=3022fps loaded with 74.9gr Retumbo.
Coated HBN bullet/bore MV=3073fps loaded with 75.2gr Retumbo.
A 0.4% (0.3gr) increased powder charge provided ~22fps decreased MV.
A 0.8% (0.6gr) increased powder charge provided ~29fps increased MV.

300 Win Mag, 210gr Berger VLD, Federal 215, IMR 7828, bullets jammed 0.008":
HIstorical uncoated bullet MV=2936fps loaded with 73.3gr IMR 7828.
Coated HBN bullet/bore MV=2909fps loaded with 73.7gr IMR 7828.
Coated HBN bullet/bore MV=2953fps loaded with 74.1gr IMR 7828.
A 0.55% (0.4gr) increased powder charge provided ~27fps decreased MV.
A 1.1% (0.8gr) increased powder charge provided ~17fps increased MV.

I did not attempt to determine a maximum pressure load with either gun/cartridge. The goal of this chronograph session was to determine the powder charge that would re-establish my historical MVs in both rifles. No indications of excess pressure were experienced in either rifle. Higher MVs are possible with higher pressure loads.

Mathematical Findings:
The 7mm Rem Mag required ~ 0.58% (0.43gr) additional Retumbo in order to obtain my historical uncoated bullet MV.

The 300 Win Mag required ~ 0.88% (0.65gr) additional IMR 7828 in order to obtain my historical uncoated bullet MV.

 

[idaho elk hunter]

Chronographed some HBN coated bullets, fired from HBN coated bores, in two different rifles. I have extensive chronograph MV data from both rifles from the prior 7 years firing the identical uncoated bullets. The MV of the first bullet fired from each freshly HBN-coated bore was NOT recorded. MVs were recorded over a set of triplicate chronographs, meaning three MVs were similtaneously recorded for each bullet fired using three separate chronographs. Chronograph agreement was excellent. Confidence in these MVs is high. My current disclaimer is that I only fired one bullet at each powder charge as this was my initial testing of HBN-coated bullet MV. But I expect this data to be reinforced with additional chronograph sessions, because my findings are similar to what others have reported.

7mm Rem Mag, 168gr Berger VLD, Federal 210, Hodgdon Retumbo, bullets jammed 0.010":
Historical uncoated bullet MV=3044fps loaded with 74.6gr Retumbo.
Coated HBN bullet/bore MV=3022fps loaded with 74.9gr Retumbo.
Coated HBN bullet/bore MV=3073fps loaded with 75.2gr Retumbo.
A 0.4% (0.3gr) increased powder charge provided ~22fps decreased MV.
A 0.8% (0.6gr) increased powder charge provided ~29fps increased MV.

300 Win Mag, 210gr Berger VLD, Federal 215, IMR 7828, bullets jammed 0.008":
HIstorical uncoated bullet MV=2936fps loaded with 73.3gr IMR 7828.
Coated HBN bullet/bore MV=2909fps loaded with 73.7gr IMR 7828.
Coated HBN bullet/bore MV=2953fps loaded with 74.1gr IMR 7828.
A 0.55% (0.4gr) increased powder charge provided ~27fps decreased MV.
A 1.1% (0.8gr) increased powder charge provided ~17fps increased MV.

I did not attempt to determine a maximum pressure load with either gun/cartridge. The goal of this chronograph session was to determine the powder charge that would re-establish my historical MVs in both rifles. No indications of excess pressure were experienced in either rifle. Higher MVs are possible with higher pressure loads.

Mathematical Findings:
The 7mm Rem Mag required ~ 0.58% (0.43gr) additional Retumbo in order to obtain my historical uncoated bullet MV.

The 300 Win Mag required ~ 0.88% (0.65gr) additional IMR 7828 in order to obtain my historical uncoated bullet MV.

The larger calibers have more bearing surface. therefore you will have to increase the load. this is shown in the 7mm vs 300 loads. You will see similar findings in bullet engineering. a 175 gr roundnose 7mm compared to a 180 gr Berger will result in the same conclusion. More bearing surface compared to little bearing surface. Hex Boron is all about the friction coefficient of bullet to barrel.

 

[Pdvdh]

The plastic tips on Nosler Accubonds are acetone resistant. They don't quickly soften up and swell in acetone like the plastic tips on the Hornady A-Max bullets did.

 

[Pdvdh]

Chronographed the 300 Win Mag and 7mm Rem Mag today to determine Maximum pressure powder charge and MV with HBN coated bullets and bore, compared to historical Maximum pressure powder charge and MV.

300 Win Mag with 25.5 inch Lilja SS barrel, 210gr Berger VLD, Federal 215, IMR 7828, bullets jammed 0.008":
Historical uncoated bullet MV=2936fps loaded with 73.3gr IMR 7828.
Max Load HBN bullet/bore MV=2971fps loaded with 74.2gr IMR 7828.
I am able to safely increase MV by ~35fps.

7mm Rem Mag with 24 3/8" factory SS Tikka T3 barrel, 168gr Berger VLD, Federal 210, Hodgdon Retumbo, bullets jammed 0.010":
Historical uncoated bullet MV=3044fps loaded with 74.6gr Retumbo.
I never reached a maximum pressure load with the 3 bullets I fired today, and I'm beginning to compress the Retumbo powder charge more than I'd prefer. I may try using a Federal 215 primer with Retumbo. Or I may have to switch to a powder with a slightly faster burn rate - perhaps H1000. I'm inclined to think that my safe increase in MV with a maximum pressure load of Retumbo will again be ~35fps.

 

[calib]

Tagging in, this is interesting to read about. I was sent the link by a fellow shooter. Would like to hear more.

 

[RockyMtnMT]

Phorwath,

Were you able to tell if there is better consistency in mv? This I think could be the best reason for using the coated bullets.

Steve

 

[Pdvdh]

Haven't gotten that far with the chronograph testing yet Steve. Lower ES & SD are primary reasons I began HBN coating bullets. Improved cold bore first round POI consistency was another. These benefits are being reported very consistently and I fully expect to realize them. Reduced copper and carbon fouling is already evident in a factory AR-15 barrel I shoot that's proven to collect copper, so that's another very consistently reported benefit.

The additional 30fps MV in my 300 Win Mag is about what I expected based on the majority of the reporting I've read. My 300 Win Mag is the best rifle I have to compare uncoated bullet MV to HBN coated bullet MV, because I've run Lapua brass at full tilt pressure loads with the Berger 210gr VLDs for the past 7 years. I'm testing that rifle with all of the same components now - even the same LOT of IMR 7828 powder - so I'm satisfied stating my gain in MV using HBN coated bullets in this rifle is ~30-35fps. Not the much higher gains occasionally reported by others.

 

[Pdvdh]

In my Brux 28" .280 RCBS Improved 30-degree (similar powder capacity as .280 AI), it required a 0.5% increased powder charge of IMR 7828SSC with HBN coated bullets to regain the original muzzle velocity I had been shooting with uncoated 160gr Nosler Accubonds. Increased powder charge from 58.4 to 58.7gr IMR 7828SSC.

It also required a 0.5% increased powder charge of H1000 with HBN coated bullets to regain the original muzzle velocity I had been shooting with the uncoated 162gr A-Max. Increased powder charge from 62.4 to 62.7gr H1000.

I reduced my original powder charge with the freshly coated HBN bore from 62.4 to 61.5gr H1000 with the 162 A-Max. That was plenty of reduction in powder to prevent overpressure on the HBN coated bore with the first HBN coated bullet. My MV dropped about 70fps. It would be wise to reduce your powder charge a bit when firing the first bullet down an HBN coated bore should you coat your bore with HBN. After the first reduced charge/bullet fired, I ramped right back up to maximum loads and then a bit more to regain my original MVs.

My 25.5" Lilja 300 Win Mag required an increase of 0.8% IMR 7828 with HBN coated bullets to regain the original MV I had been shooting with the uncoated 210gr Berger VLDs. Increased powder charge from 73.3 to 73.9gr 7828.

This provides an idea of the increase in powder it will require to regain your original MV should you start shooting HBN coated bullets.

 

[RockyMtnMT]

Thanks for posting your results Phorwath. Are you going to stay at original mv? Or are you going to see if you can gain the possible extra fps? I am guessing you will stay so you don't have to redo drops.

Steve

 

[SHRTSHTR]

I have followed this thread and like what I am reading. Ordered my HBN kit on Monday should get it today .
Very exited to see what it does in my 338 LAI. Lower ES is what I am looking for. Added velocity will be added bonus but not the reason for trying it.
Good info as usual Paul! Thank you.

Ray

 

[Pdvdh]

Thanks for posting your results Phorwath. Are you going to stay at original mv?
Steve

For the time being I'm just trying to re-establish original MVs in the rifles with established loads. That seemed to be the wisest use of my time and efforts, since I have a number of rifles/loads. That explains the sort of information I'm able to share to date.

It's always tempting/fun to pursue the additional MV , and I'm sure I'll do some of that - eventually - in my primary hunting rifle.

 

[RockyMtnMT]

Maybe I should start a new thread for this but it seems to fit the discussion.

Has anyone tried WS2 tungsten disulfide powder? Compare to HBN? Seems to have better coefficient of friction.

Steve

 

[barnesuser28]

So far i have shot 15 WS2 coated 300 grain berger OTM out of my Savage .338 Lapua. this is in a new barrel and i havent shot any uncoated through it so i dont have a baseline but i was able to get 2820-2830 fps with 102 grains of RL-33, in a 26" tube! I decided to use WS2 and not HBN because of the lower COF and ive read that sometimes the HBN doesnt want to coat evenly. I have noticed that you NEED to get your bullets completely degreased before tumbling in WS2 or the results are patchy. I use 91% isopropyl alcohol to clean them and deposit it in the bore. I tumble the bullets in a pill container with about 1/2" of zinc coated bbs and about 2 grains of WS2. Tumble for 1.5-2 hours and wipe them with paper towels to get the bulk off and polish with an old sock. I bore scoped the barrel after the 15 rounds and you can definitely see there is some WS2 deposited in the bore. I will try it in some other guns that i already have a baseline load for and see what results i get. I think i am going to try the 195 berger in my 284 win, this will likely be a perfect candidate for this testing.

 

[Cold Trigger Finger]

I just recently got set up to coat bullets with HBN. I use acetone to clean the bullets. Dry them on paper towels. Put them in Mason 1/2 pint jars and put 1/4 teaspoon hbn in on top of the bullets. Put the lids on TIGHT and tumble in a Harbor Freight double drum rock polisher. And tumble for 2 hours. The bullets come out fully coated and I polish them in 2 cotton socks. All I've done so far are 6.5 bullets. Did a box of 130 gr Barnes TSX and almost 200 140 gr Nosler CCs. I've got some of the 140s loaded to shoot in my 6.5 Creedmoor. I have both uncoated and coated 140CCs loaded with the same powder charge from the same bottle of powder. Brass is from the same box of new brass. Same primers. Same oal.
I haven't shot them yet. Just got back home but hope to this week. I'll report back with my findings. My load is 45.3 gr Superformance. Barrel length is 18.6"
I'm definitely interested in the velocity but as this is a hunting rifle that I want to use for lr hunting. I'm most concerned with the cold bore shot being in the group.