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+--- Thread: Broken 6mmAR Bolt (/showthread.php?tid=18864)
Broken 6mmAR Bolt - Yondering - 11-23-2020
SHORT-N-SASSY Wrote:As we await a response from Hornady, I researched the issue:
Comparing Advertised Ballistic Coefficients with Independent Measurements
http://www.65grendel.com/forum/showthread.php?10389-Litz-Verified-BCs-Good-News-for-6-5mm-Bullets&p=114343&viewfull-1post114343
(See the attached PDF file) The Report covers January, 2009 thru June, 2011.
Introducing the ELD-X: Hornady's newest and most sophisticated bullet is a BC breakthrough
http://www.thefreelibrary.com/Introducing+the+ELD-X%3A+Hornady%27s+newest+and+most+sophistacated+bullet...-a0436981663
And, as stated by BluntForceTrauma in his July 16, 2015 Report, Litz found the Ballistic Coefficient of the Sierra 6.5mm 123-grain MatchKing projectile to be 0.522, not 0.510, as advertised.
The following compares the 6.5mm Grendel (A)123-grain Sierra MatchKing, Ballistic Coefficient (G1) - 0.522, muzzle velocity (12.5" Barrel), 2420 fps, with the 6mm ARC (B) 108-grain Hornady ELD Match, Ballistic Coefficient (G1) - 0.536, muzzle velocity (12.5" Barrel), 2380 fps, to 500 yards, w/ 10 mph crosswind ---
![[Image: 12-5-6-5-G-123-MK-v-6-ARC-108-ELD.gif]](https://i.postimg.cc/sXMB2mb3/12-5-6-5-G-123-MK-v-6-ARC-108-ELD.gif)
I know this thread is a little old, but thought Id offer some real world data. IME your estimated velocities are optimistically high for the Grendel and pretty low for the ARC.
My example is the 243 LBC rather than the ARC (a whopping .030 more case capacity, woohoo), but I have nearly identical 12.5 6.5 Grendel and 243 LBC SBRs for comparison. Using Leverevolution, CCI 450, and the same Lapua brass in both, the Grendel will handle ~2380 fps with the 123 ELD, and the 6mm will do 2500 fps with the 105 BTHP. (I dont use the 108gr but Hornady loads both to about the same velocity based on user reports.)
The difference in actual trajectory between these two cartridges at 600 yards is pretty significant (I shoot across a canyon at that distance all summer); 4.7 mils for the 243 vs 5.4 mils for the Grendel with that full tilt load. I should note that my Grendel doesnt shoot well with that load though (but the 243 does), and the accuracy load for that Grendel is 2310 fps for 5.9 mils confirmed drop. 1.2 mils more than the 243, and with more wind drift and less velocity.
Ill also add that Im on 8 & 9 loads with the Lapua brass in that 243 load, so Im not pushing it beyond reasonable limits. I do like my Grendel, but the 6mm flavor has some real advantages in trajectory and wind.