Re: Will an 18.5" 1-in-10" twist .308 shoot out to 1K?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: pointblank4445</div><div class="ubbcode-body">I don't mean to hijack, but what is it about the 168grain that makes it key-hole and not the lighter 155 or heavier 175? </div></div>
The 168gr Sierra MatchKing is a fine, accurate bullet for 600 yards. I have shot at lot of it around the range or closer in and it works really well. I believe the earlier M118 used that bullet and snipers rarely take shots with a .308 or .30-06 beyond 5-600 yards so it did very well.
However the design of the bullet is such that when it goes transonic the disturbance causes it to lose its point-on attitude and it starts to tumble in flight. It will continue in its trajectory but now it may be tumbling and this means it will hit the paper in whatever attitude it's in at the instant it hits the paper.
I believe the reason it is so affected by the transonic passage is that most of it weight is in the rear of the bullet and only for a relatively short distance; the boat tail is short. The 175gr is a somewhat different configuration and its boat tail is longer. In short the 168gr SMK seems to have the exact weight distribution that causes it to be a great bullet while supersoninc, but to also loose its bearings in the transonic passage.
I believe this is only for the 168gr SMK, I do not think the 168 A-Max is affected in a similar manner. I shot plenty of 168 A-Max but never past 600.
It sort of makes you wonder if flat-base bullets are more susceptible to transonic tumbling compared to boat tail bullets.
