Coated bullets and optical chronographs?

[Critter Picker]

While I am certainly no engineer and do not have the equipment to test lubricity, but after many years of dealing with all types of equipment, ranging from lawn mowers; cars, trucks, heavy equipment up to including large back hoes and dozers, not to mention piston and jet aircraft, not to mention the vast improvement in all types of lubricants from 10 in 1 and sewing machine oils, to heavy duty engine and high temp aircraft engine oils it has been my experience that, by increasing lubricity you decrease friction, not the opposite. (how is that for a run on sentence?) Adding a lubricant coating to a bullet will decrease the friction of the bullet traveling down the barrel, which should cause a slightly higher muzzle velocity than an un-lubricated bullet. You should not have to bump the powder to get the muzzle velocity back up to what an un-lubricated bullets speed is. For those of you who aspire that the coating increases the size of the projectile resulting in an increase in bullet diameter, the thickness of the lubricant would be measured in ten thousandths of an inch, which is essentially meaningless. There is more variation in bullet diameter and weight during the manufacturing process than the coating could ever change. Laws of physics do not arbitrarily change.

I think what happens (in my mind) by decreasing resistance and/or friction on the bearing surface, the bullet slides down the barrel so easy that the powder doesn't have time to burn completely. We all know that a crimp can increase pressure, so it stands to reason, that decreased friction can lower pressure.

 

[RegionRat]

Adding a lubricant coating to a bullet will decrease the friction of the bullet traveling down the barrel, which should cause a slightly higher muzzle velocity than an un-lubricated bullet.

Smokeless powders are a deflagrant rather than an explosive, so they have a "feedback" from the pressure.

The initial starting pressure from retention, sealants, crimp/no-crimp, bullet engraving, the friction, obturation, the bullet's inertia, etc., all have an effect on the total pressure pulse. If we alter the start, we alter the peak and area under the pressure curve.

As it turns out, if we do things that reduce the starting pressure, we will reduce the peak pressure and area under the curve, when all other things are equal.

This is why the application of a "lubricant" will cause us to need more powder to get back to the same velocity.

 

[Teri Anne]

Hi Terri Anne.

No, the bullets coated in MoS2, HBN, etc,, will not have their first order Doppler radar reflection affected by their coating. They will radar track just fine.

The surfaces of stealth aircraft are called RAM (Radar Absorbing Materials) and are pretty unique in how they accomplish this.

In the OP's post, his optical chronograph works because the bullet is opaque and the color or reflectivity has nothing to do with affecting the ProChrono. It triggers on the shadow, which can be affected by the cloud cover and sun angles, but not really affected by the bullet finish. The bullet is opaque so it will be triggering as long as the shadow tracks through both "windows", just like MagnumMania says up above.

Being retired my budget does not allow for the purchase of a radar chronograph. I have a conventional one that is a royal pain in the butt to set up, but it works relatively well. The $500 or so that it would take to buy a radar style chronograph buys a lot of primers, powder and bullets which results in a lot of on range fun. As mentioned before, I am more into accuracy than speed. I will bow out of this discussion and simply go back to punching tiny groups into targets and animals.