straight question 308 vs 6mmBr

[dafar]

How does the 6mmbr hold up against 168 grain 308 at 1000 yards

 

[blaster4]

I don't think 168 gr bullets are the best choice for 1000 yds with the 308. i think the 175 gr MK is more popular at that range.

 

[Caduceus]

Not to mention that the velocity figure you are using for the 168grn in the 308 is fairly optimistic. Not unobtainable, but I personally can only get 2800fps from that bullet in a 26" barrel. To do that requires me to exceed the published maximum load, using Varget. The cases seem to do OK for pressure but it is not the load I want to live with every day.

It actually shoot a lot better when loaded more mildly - down to 2685fps. Works fine to 600yards but 1000yards is getting iffy due to subsonic transition. In my opinion, the best projectile to go to 1000yds in the 308 is the 175grn Sierra. Don't let the fact that the Palma shooters use the 155 convince you that is a better choice - they only do it because the rules say they have to.

 

[Forum Boss]

Another take on things,using PointBlank software):

105gr Scenar at 2900 fps,Std 6BR)
10 mph Crosswind drift: 74.60"
Time of Flight: 1.458 sec

168 SMK at 2750 fps,.308 win)
10 mph Crosswind drift: 97.50"
Time of Flight: 1.645 sec

I think 2750 fps is more realistic for a 168, unless you're using a long Palma barrel.

Note, there are many people who believe stated BC doesn't tell the whole story. These folks believe a heavier bullet will perform better in the wind than a lighter bullet with the same BC. There is some anecdotal evidence to this effect in 1000-yard matchs. Balance that against the fact that the .308 has a longer time of flight.

Personally, between the two, I'd much rather shoot the 6BR. Less recoil and higher BC, and I believe the Scenar will shoot up to its BC. As for the heavier "bucks the wind better", you'll get opinions on both sides. Performance in cross-winds should be predictable from the BC, by definition. However, there may be some subtle factors the ballistics software can't predict.

 

[dafar]

Thank you for all of the info guys. I gives me alot to think about

 

[6Dasher]

When shooting a 308 at 1000, you may want to use the 155 grain bullets instead. Higher BC and speed... optimized for Palma and such not many people seem to realize these properties out of a lighter bullet,heavier = better is not always true).

 

[Caduceus]

When shooting a 308 at 1000, you may want to use the 155 grain bullets instead. Higher BC and speed... optimized for Palma and such not many people seem to realize these properties out of a lighter bullet,heavier = better is not always true).

Higher BC than what?

From Sierra's website: 155 MK BC = .450, 168 MK BC = .462, 175 MK BC = .505,.496 below 2800fps)

Sure you can push lighter bullets faster but the 155 Palma bullet does not have a higher BC than either the 168 or the 175 Matchking.

I restate what I said earlier: Palma shooters use the 155 because the rules say they have to. If bullet selection was not restricted by the rules of the match, you can be sure a good proportion of them would switch to the heavier bullets.

 

[memilanuk]

Actually, you might be surprised on that one... pushing a 175 or 190 fast enough to keep up w/ the 155 SMK, even out of a 30" barrel, is kind of borderline out of a .308 case. The 155gr Scenar makes that even less likely. Because the only place that 155's are really *required* is in International competition, it's not that uncommon to see U.S. shooters using 175's or 190's if they want to. I spoke w/ a person well placed on the U.S. Palma team,coach) about the 190's and he mentioned that he and others used to use them, but after coming off the line w/ both 155's and 190's w/i a click or two of one another for the same conditions, considering the accelerated barrel wear they experienced w/ the 190's vs. the 155's... most of them switched to just using the 155's... the 'disadvantage' wasn't that noticeable in reality, the barrels lasted considerably longer, and that's what they would have to use come the actual international matches anyway...

YMMV,

Monte