Higher MV with hBN?

[normmatzen]

I have read a couple reports of folks getting HIGHER muzzle velocities with hBN than with plain bullets.

I presently use Moly and see a lower MV with coated bullets.

Can any one explain this phenomana in non-anecdotal terms?

My only guess is that the coefficient of friction is so much less than bare copper or even Moly, that the friction is trivial compared to simple acceleration of the mass of the bullet?

 

[AKDaddy]

I just ran a test yesterday, in which I loaded hBN bullets to the same specs as uncoated bullets that I have extensive cronograph data for. The hBN bullets shot about 60 fps slower. So compared to uncoated (ie "plain") bullets I got a lower MV, which was not unexpected.

Note that my data does NOT compare hBN bullets to moly bullets. I have no data for moly bullets. I'll let others with experience with both coatings speak to that.

 

[Holland]

Les friction is les pressure building resulting in lower velocity
On the other hand, you can load more powder with coated bulled, because of the lower pressure

 

[ar15topgun]

Some are reporting higher velocities using hbn. Can this be explained?

 

[zfk55]

Read Holland's post right above yours. He explained it in simple terms, or go here and read the whole thing...... http://www.patentstorm.us/patents/7197986/description.html

zfk55

and.......... Higher velocities with the same load in a newly hBN'd barrel and impact coated projetiles is completely erroneous information.

 

[ar15topgun]

At the end of the article he states that an increase in velocity is not unusual as well as a increase in barrel life when the bore and bullets are treated with hbn. The article is very interesting but it would be nice to be able to veiw the figures and graphs also. Tim

 

[zfk55]

Ok, ar15T, I'm a member there and I'll pull the pertinent parts for you when I get a bit more time and post them here.
In all 9 rifles treated and tested thus far every single one of them dropped a nominal 75+fps with the same projectile, load and reloading methodolgy.
Back when I can.

zfk55

 

[Benjerman08]

I shoot hbn on 115 dtacs exclusively. They shoot about 75 fps slower always.

 

[ar15topgun]

Thanks, I look forward to reading the study in its entirety. Tim