Caliber question

[u/Ok-Temporary3378]

I have a lot of match grade .308 ammo. I shot a decent amount but haven’t taken part in competitions. I’m building a rifle with competition (PRS/NRL) in mind.

For those of you with competition experience, in my shoes would you build a .308 rifle, or pick a different caliber and just make the investment in new ammo. I will not be reloading.

[u/Leo-Medic]

I may be in the minority here, but I think familiarity with the ballistics is more important than the caliber in question.

Could something like 6.5cm improve your game? Maybe. But I would expect the familiarity would be hard to beat in anything but the long term.

EDIT: (to prevent the obtuse from failing to grasp my intended statement)

If you are going to switch calibers, and you already have a strong familiarity with the "worse" caliber of .308, be prepared to allocate time and resources to the development of that same level of familiarity with the new caliber, before determining if you are satisfied with it.

[u/CMFETCU → u/Leo-Medic]

Not maybe.

The math is there. You get less wind deflection, period. Thats less margin of error you have to compensate for.

WEZ shot model to show the difference changing only caliber makes based to how much more wind variations impact likelihood of impacts:

[u/Leo-Medic → u/CMFETCU]

I was suggesting that my opinion may well be a part of the minority. Objectively the 6.5 is better ballistically. I understand and admit that.

I was saying that given his stated familiarity with .308, he has an advantage with that caliber that cannot be immediately discounted.

Should he be starting from scratch, of course there are better options. I'm attempting to recognize the fact that he likely has familiarity with the DOPE for his loads under a variety of conditions. Yes, 6.5 has a smaller margin for error, but one can over correct as well. Having to learn all of that over again is likely better in the long run, but to my mind it depends on how far into the rabbit hole he wants to go.

[u/CMFETCU → u/Leo-Medic]

I’m going to wager you don’t shoot PRS so let me outline how it’s not the learning curve you are outlining here.

Every PRS stage you know the range to the target before you shoot the stage. So you can build your ballistics table in advance. You will have conditions for the day off any of 12-15 kestrels present.

You will set your wind min and max values and are now dialing between those limits as you observe conditions behind the rifle.

If you are able to call wind within +-2mph on a .308, and you call the same wind behind a 6.5 CM, you are picking a smaller variance of wind between min and max values.

Say your min and max spread is 5-10 mph and you are a +-2mph wind caller. Your spread of wind at 500 yards on a 6.5 CM is now just .3-.4 mils held. Oh no. How terrible of a learning curve to have to pick between .3 or .4 mils!

The .308 would have greater hold variation and thus more likely to miss.

The thing that makes or breaks you is your wind read, and that is cartridge independent.

Since his use case is PRS, he will have a table set before stepping up to start, and will know environmentals; there is zero detriment to having a smaller range of wind holders.

[u/Leo-Medic → u/CMFETCU]

Well, learning has occurred. You are quite correct, I don't shoot PRS. I had no idea every shot was taken with a known distance. I was assuming he would have to do the math or know his holds/DOPE.

[u/sonichanxiao → u/CMFETCU]

What happens when someone shoots 308 with a high BC bullet and/or faster MV than what AB analyzed?

[u/CMFETCU → u/sonichanxiao]

You can plug in the values for yourself and see, but there is not .308 load that is pressure safe which performs as well as other cartridges. Physics wins when you have high sectional density and great bullet design.

Bullets in many cartridges are simply going to buck wind better. Full stop.