Testing Friction Reduction of Bullet Coatings

[Michael Courtney]

Then you get into the mechanics of compression which I know nothing about of course. my thought process is, when you compress something it has to go somewhere right? When your lead core is totally encapsulated in a jacket, where can it go?

In match hollow point bullets, there is an air space in the front of the bullet. The lead can expand forward.

 

[Bullet bumper]

If they said that MoS2 coating did not change velocity then their testing is total crap. It always lowers velocity with the same powder loads . The reduction in friction changes the pressure time curve so the bullet gets out before experiencing the same chamber pressure than the uncoated bullet does .
It's a bit like reducing the powder charge . You have to increase the powder chatge slightly to get back to the same velocity as an uncoated bullet.
I know that sounds odd when friction is being reduced but the push on a bullet is a function of pressure over time , If the bullet moves out easier the bore volume behind the bullet is increased much quicker as compared to the burning rate of the powder and has the effect of lowering the total chamber pressure that the bullet sees before it exits the bore . All else being equal that is .
Then we have the variables of many different types of coating systems that all go under the same names but are very dfferent in chemical make up and application.
Some factory bullets say Moly coated but infact don't have ANY MoS2 on them .
It is one of those things that you do it yourself and if you like it then that is all that matters . If we listened to all the nay sayers few new ideas would see the light of day. I have been using my own Moly coating process for many years and think that it does have some benifits when firing long strings of shots without having to clean . Not every shooting situation suits coated bullets.