02-10-2020, 01:19 PM
lazyengineer Wrote:Thank you. This actually was very helpful.
I've grown to dislike the 123. On-paper, it's perfect bullet. In practice, it's been a nightmare of a bullet for me in the Grendel; 3 BBL's and multiple manufacturers. When I run it mag-length slamming through an AR gas system, is very expensive 3-4 MOA ammo for me.
Thinking it's me, I load it up in my Creedmoor, that I know is a 1 MOA gun. And again, 123's in a Mag-Length semi-auto magazine, give me a nice 3-4 MOA performance, even in the creedmoor. Yet when I tried some 120's this weekend, my group sizes shrank to better than half, and are even crowding 1 MOA (not quite, but close), in my Grendel.
Your post was very helpful in explaining why.
LE:
Basic difference between a Tangent and Secant ogive. Look at any of the bullet maker web sites and all of them say the Secant or VLD designs are more sensitive to seating depth and chamber design. Also, their BC's are variable with the highest being when the bullet is driven way faster than a guy will get from a Grendel cartridge due to powder capacity. Yes, the VLD's show slower incremental decreases in velocity over time than the Tangent designs and any time a guy can get his bullet to the target faster is better because the wind has less time to push it around. The other side of the sword is that getting there faster means nothing if a guy shoots 8's at 600 or misses targets at 800 because he didn't get the right seating depth, use the right chamber design, or the right rifling twist.
If a guy wants good results with almost any safe load using any chamber and conventional twist rate, and without spending a couple hundred on components to run ladder tests using different powders and primers at the longer ranges they are shooting, get a bullet with a Tangent or even a Hybrid ogive. I have found the Lapua 108 and 123 grain bullets to be a super good compromise between the more strict VLD's like the 123 Sierra and the Tangent ogives like the 120 Sierra. The problem is the Lapua bullets are so expensive that most guys will not buy them unless they are highly competitive and have found these bullets to be the difference between winning and losing.
The 120 Sierra will be fine on two minute steels to 800 yards at sea level providing a guy can dope winds as well as they could shooting the old 168 grain Match King loads used in High Power years ago. Granted, these loads are not competitive anymore because of their low velocity compared to the various 6mm and 6.5 mm cartridges used competitively today but at least with these loads you can bet that poor performance wasn't due to the bullet.
LR55