Moly?

[Bullet]

Do I have this right? There seems to be two opinions about the drop in pressure and velocity when using moly.

Mr. Vaughn’s - Norma and others

Vaungh - "The drop in pressure and velocity is not caused by a reduction in barrel friction as proposed by Norma and others. It is caused by the hot propellant gasses (5640 F.) vaporizing the coating resulting in a cooling (about 400 F.) of the propellant gasses.”

Norma - Moly is a superb friction reducer and it’s bearing capacity is beyond the yield point of known metals. When a molycoated bullet enters the throat and travels down the barrel it has less friction than a ordinary bullet. So it is not surprising to see a lower pressure. We have not done any huge tests with many calibers but these 3-5% has been there every time.
If pressure is reduced velocity will also be lower with the same charge. The interesting thing is that velocity is not reduced as much as pressure. Thus, by increasing the charge you can usually get 1-2% higher velocity with moly bullets.


Does Mr. Vaughn agree with this? - From above Norma - Thus, by increasing the charge you can usually get 1-2% higher velocity with moly bullets.

 

[30Cal]

I don't think it really matters what exactly is going on. You get a lower pressure with moly and can bump up the powder charge to make a gain in velocity. I would like to point out that the gain is small and isn't going to make a significant difference in drop or wind drift.

Ty

 

[Bullet]

30Cal - “I don't think it really matters what exactly is going on.”

I believe you are right in a practical sense.

One of the things I find curious with regards to guns is how there is still debate over certain issues. After all this is almost 2006. I thought all these debates would have been settled by science by now. Apparently science isn’t up to date with regards to guns or the shooters are behind the science.

I don’t have Vaughn’s book. I just wondered if he believed that given same pressures moly would attain more velocity?

 

[jerkface11]

I don't know if moly drops presures or not. But in my testing it lowered VELOCITIES. So while it may allow you to work up a "hotter" load you'll need to just to get the SAME velocity. Of course this was a very limited test. When i get some more spare time i'll be a little more in depth.

 

[The Bushmaster]

If the heat is absorbed by whatever your velocity would drop as well. Temperature and pressure go hand in hand. I would go with less friction myself...

 

[antarti]

Given a projectile with less friction, wouldn't using a faster powder produce a more efficient load?

"More efficient" being a load that was faster than the non-Moly equivalent with the same charge?

I don't know how many shades of "faster" the propellant would need to be to take advantage of the reduced friction, but shouldn't this stand to reason?