JLK .264 135 bullet BC???

[brianc74]

Does anybody know the G1 and G7 BC of the new .264 135 grain VLD bullets.

I am shooting them out of my Lane Precision 6.5 GAP4s Rifle. The barrel is a Proof Research 26” Barrel with a 1-8 twist. Accuracy is at 3150fps.

Brian

 

[fredo]

I'd swag it at a G1 of .625, then shoot to 'tune' it in/confirm value for yourself...

Got a good load for em, yet?
Is that 3150 MV, consistent?

If so, you should be able to extrapolate a 'tuned' b.c., according to your bullet drop at distance. Then, it won't matter what anyone else tells ya the b.c. is... cuz you'll have proven it for yourself, with dope from your load, out of your rifle.

In the end, that's what you wanna do, anyway! Just make double sure that MV is spot on close, and your target distance is, likewise on the $$$ to the yard. Lastly, use a PROVEN REPEATABLE scope that corrects true to measure. Then, you'll have all your 'constants' set up to the point where derving b.c. is the one variable that can be 'tuned'...

So, use .625 to start, at say...800yds. If hitting consistently LOW, then LOWER the b.c. value. That will make ballistic calculator spit out more correction is required. So, you'll dial more UP, and begin to hit on level. Vice versa, if hitting HIGH...

Good luck & have fun!

 

[boltfluter]

Anyone have an idea on the BC?

Thanks, Paul

 

[mikecr]

CALCULATED
G1 ICAO = .652
G7 ICAO = .317
This with parameters provided by JLK, filling in holes for the rest (guess), and 3150fps.
Biggest influence to the guess is unknown meplat diameter. I used .050,, at .062 =>
G1 ICAO = .604
G7 ICAO = .294

Point meplats to .020
G1 ICAO = .723
G7 ICAO = .351

Meplats are a big influence. Add otherwise normal variances together(all of them) and they don't approach meplat influence.

 

[dcali]

A side tangent: the reason the meplat has such a big impact on calculations is that when you change it, you indirectly change the other ogive parameters (length/headshape). It’s not the same as taking an existing bullet and pointing it, which is changing only the nose tip geometry (hopefully for the better)

It’s a subtle but important distinction. You can’t take a .062 .294 BC and turn it into a .351 just by closing up the point to 0.020. Doing so would be more akin to blunting the nose, which could actually hurt BC.