bullet pointing and BC consistency

[solst_ice]

According to Bryan Litz, pointing of bullets (those without a tip) can increase their BC.
But how can I know the new BC they got?
Wouldn't that mean, that I cannot rely on the BC data provided by a ballistic solver anymore, but would have to provide own data for the BC? Otherwise, all the calculations would be based on the BC of unpointed bullets.

Does anyone have any experience with that?

 

[Seandradamus]

Yes , increase the BC in your solver until it matches up . For instance 105 Hybrids increased to .594 g1 when pointed for me.

 

[solst_ice]

Yes , increase the BC in your solver until it matches up . For instance 105 Hybrids increased to .594 g1 when pointed for me.

Interesting, but how to do that? Do you measure the drop at a range? But other factors, like environment, muzzle velocity variation would have in influence on that.
I've no idea, how to measure the real value of the new BC.

 

[lte82]

Interesting, but how to do that? Do you measure the drop at a range? But other factors, like environment, muzzle velocity variation would have in influence on that.
I've no idea, how to measure the real value of the new BC.

The short version: Shoot at a couple of distances, say 500 & 1000, with all of your environmental variables input correctly. Chrono your load, then adjust your BC (and possibly velocity, if absolutely needed) so that your solver gives you correct elevation for centered hits at both the mid range and long range distance. The solver will theoretically now track your trajectory properly.

 

[spife7980]

I entered my stuff all exactly and at 1k I was hitting a third of a mil or something high. I adjusted my bc from .280 to .310 so that the calculator matched the real world results. Pointing just means you need to measure and make an appropriate adjustment.

 

[Sheldon N]

I shoot pointed 105 Hybrids, and have also used pointed 7mm 195 EOL Hybrids. Approach is the same as I use for confirming data on unpointed bullets. Get a good zero, get solid velocity data from a quality chrono like a Magnetospeed, get good environmentals and then shoot on a reasonably calm day from 500 yards out to 1200+ yards. The closer targets confirm that everything is tracking true, then I'll note how much if any elevation adjustment is needed at 900-1200 yards to get waterline impacts. I will tweak the BC in my solver to true up the data.

I've typically seen a gain of .010 to 0.015 G7 points from non-pointed to pointed bullets.

Keep in mind that BC will vary barrel to barrel depending on all sorts of factors. I've got one barrel that shoots pointed 105 hybrids at .275G7, then another barrel that shoots them at .292G7. Same speed, same chrono, same powder, same box of pointed 105 hybrids. Things like bore diameter can affect the shape of the bullet and the BC so you need to shoot to know what you're dealing with.

 

[solst_ice]

Pretty interesting.
The only problem I got, that I can shoot up to 300m only most of the time.

 

[spife7980]

In that case don’t worry about it. When you do finally go longer just see what it does and adjust it.

 

[solst_ice]

I wish, I'd have over a mile in front of my house to train every day.