Coated bullets and optical chronographs?

[Teri Anne]

Optical chronographs work by the bullet casting a shadow, they do not need a reflection of any kind to operate. If the shadow is not directly above and centred in BOTH screens, it will give false readings.
They actually work best on overcast days because the light is dull and the shadows are sharp.

Cheers.

We are talking apples and oranges here. You are talking the old conventional time/speed/distance chronograph while I am talking new radar type chronographs. Different technology but something to think about when using the radar type chronographs.

 

[Rflshootr]

Coatings also add lubricity to and decrease resistance to the bullet. Generally, you have to bump the powder to get the same velocity as an uncoated bullet with the same charge. I'm almost certain that Nosler's data was shot with uncoated bullets.
Clean the barrel very well before shooting the uncoated bullets. Leaving any of the coating in the barrel will not give true results.

 

[Critter Picker]

While some may think that the color of a bullet should not matter, when it comes to using a radar type chronograph it may. Radar uses reflected signals in order to determine time, distance and speed. Shiny things, cars, aircraft and bullets will reflect the radar signal back much more reliably than a dark/flat object. You may note that most military aircraft, especially those of stealth design all have dark or flat finishes. This is because the radar signals are absorbed or the reflection decreased to keep radar from picking them up. In my sometimes muddled mind, it seems that it would work the same on bullets. Shiny bullet, good reflection, dull bullet limited or no reflection. Anyone else have thoughts on this?

Interesting thought. Someone above my pay grade would have to answer that.

 

[Mikecr]

Coatings also add lubricity to and decrease resistance to the bullet. Generally, you have to bump the powder to get the same velocity as an uncoated bullet with the same charge. I'm almost certain that Nosler's data was shot with uncoated bullets.
Clean the barrel very well before shooting the uncoated bullets. Leaving any of the coating in the barrel will not give true results.

That's only with use of moly, and not due to reduced friction.
Moly cools the charge while evaporating. This lowers MV per charge, and acts to reduce erosion, but reduces accurate barrel life if not well managed.

Other dry coatings, even slipperier than moly, do not reduce MV.

 

[MagnumManiac]

We are talking apples and oranges here. You are talking the old conventional time/speed/distance chronograph while I am talking new radar type chronographs. Different technology but something to think about when using the radar type chronographs.

I see zero relevance to this and your other post. The OP is not using a Radar generated chronograph, he is using an ocular chronograph…

Cheers.

 

[atblis]

Dark bullets actually read more reliability on the optical chronographs. Sometimes I'll take a sharpie and color shiny bullets on bright days when I am getting lots of errors. Definitely helps.

 

[cohunt]

I have a pretty accurate load in 270w with the nosler 130gr bt--- I tried the identical load with the 130gr silvertip bullet and my speeds were slower, I asked nosler about it and they said the black coating they use on the silvertip bullets reduces friction in the barrel and I may need to add slightly more powder to achieve the same speed as their standard ballistic tip bullets

 

[Philward]

I found this bit if information on nosler forum from i think one of their guys or at least someone who is experienced in loading e-tips. "When using e-tips consider the starting load data as the middle charge for a given bullet weight and consider the middle charge for standard bullets as the max charge weight. And these bullets seem to like 0.100" jump." I know the load data says to start low because these non lead core bullets react different to pressure. I have seated the bullets to 0.100" of the lands. 2 things to try: load some of the uncoated bullets and shoot them and 2, start increasing powder charge until i reach pressure of some kind. That won't happen for another couple weeks due to hunting. I guess #3 would be a faster burning powder.

 

[Philward]

I have a pretty accurate load in 270w with the nosler 130gr bt--- I tried the identical load with the 130gr silvertip bullet and my speeds were slower, I asked nosler about it and they said the black coating they use on the silvertip bullets reduces friction in the barrel and I may need to add slightly more powder to achieve the same speed as their standard ballistic tip bullets

Hmmm , interesting.. similar to Barnes and their blue coated bullets from the past, XLC bullets i think they were called

 

[Critter Picker]

On one hand,that's a big surprise, on the other hand, that makes a lot of sense.

Personally,I didn't expect that!

 

[Philward]

With all that information about the charge weights nothing was mentioned about the velocities being equivalent, i.e. will the mid powder charge be equivalent to the velocities at the higher powder charge or should I expect the mid charge to produce the same velocity as the lead core bullets.

 

[RegionRat]

Anyone else have thoughts on this?

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.