BTHP vs. AMax

[5gnut]

Any opinions on 168 gr. BTHP vs. AMax in .308 out to 600 yds.

[Cowboy T]

Out to 600 yards, no problem with either. Their BC's (Gen 1) are very similar, with the AMax at 0.475 and the BTHP at 0.450.

When you start getting to 1,000 yards, that's where you see a difference due to where the bullet goes transonic. Transonic for the 168gr A-Max, with the standard (not "Superformance") Hornady Match ammo is about 1,050 yards, depending on your barrel length (22" Ruger American Rifle, in my case). The BTHP will hit transonic a little sooner, maybe 975 to 1,000 yards.

[liber]

Out to 600 yards, no problem with either. Their BC's (Gen 1) are very similar, with the AMax at 0.475 and the BTHP at 0.450.

When you start getting to 1,000 yards, that's where you see a difference due to where the bullet goes transonic. Transonic for the 168gr A-Max, with the standard (not "Superformance") Hornady Match ammo is about 1,050 yards, depending on your barrel length (22" Ruger American Rifle, in my case). The BTHP will hit transonic a little sooner, maybe 975 to 1,000 yards.

Cowboy,

I don't shoot that far yet, but am curious. If the BTHP goes transonic at 975-1000, doesn't that have a huge effect on target shooting at 1000 ?

Seems when it goes transonic it becomes unstable as that happens and then stabilizes again after...if it does that just prior to hitting 1000 yards that would seem like a bad choice for 1000?

[ar15barrels]

If the BTHP goes transonic at 975-1000, doesn't that have a huge effect on target shooting at 1000 ?

Seems when it goes transonic it becomes unstable as that happens and then stabilizes again after...if it does that just prior to hitting 1000 yards that would seem like a bad choice for 1000?

You don't want to be using EITHER of the 168gr bullets at 1000 so it does not matter when the bullet goes transonic.
Use the 178 BTHP or a 175 SMK.

[highpower790]

Out to 600 I have found the amax to be 1min better.

[boomer135]

Don't forget the Sierra 175TMK came out this year with an improved BC. I just ordered some to test out.

https://www.sierrabullets.com/products/new.cfm

[liber]

You don't want to be using EITHER of the 168gr bullets at 1000 so it does not matter when the bullet goes transonic.
Use the 178 BTHP or a 175 SMK.

Ok, point taken. These must go transonic at a further distance?

EDIT: Randall I have seen some data that suggests that the 175 gr BTHP goes transonic around 800 yards, still trying to get accurate data (you know how the internet is). My question is, if this is the case does that mean that the 175 SMK can go transonic and then become stable again at 1000 ? I currently am loading 168 SMKs and just got some Nosler 168 Custom Competition (BTHP) to try, but shoot mostly at 200, so there's no concern there. Just curious for when I do get the itch to go farther.

[5gnut]

Thanks for the info. Nice to see a discussion that doesnt get trampled by the egos of the keyboard commandos

[ar15barrels]

I have seen some data that suggests that the 175 gr BTHP goes transonic around 800 yards, still trying to get accurate data (you know how the internet is). My question is, if this is the case does that mean that the 175 SMK can go transonic and then become stable again at 1000 ?

Are you shooting a 10" barrel?

[Cowboy T]

Cowboy,

I don't shoot that far yet, but am curious. If the BTHP goes transonic at 975-1000, doesn't that have a huge effect on target shooting at 1000 ?

Seems when it goes transonic it becomes unstable as that happens and then stabilizes again after...if it does that just prior to hitting 1000 yards that would seem like a bad choice for 1000?

Yes, you're right. I would choose something heavier, like the 178-grainer for that distance. It also depends on your air density, so when you start getting close to 1,000, you have to take that into account. The 168-gr A-Max, I know for a fact will get out to 900 and stay precise. But I personally wouldn't go beyond that for precision shooting, with either it or its BTHP sibling.

You don't want to be using EITHER of the 168gr bullets at 1000 so it does not matter when the bullet goes transonic.
Use the 178 BTHP or a 175 SMK.

Agreed with the first part of your statement, but disagreed with the second part. It's all about when the bullet goes transonic; that's the point of the heavier bullet for target shooting. That's why I use the 178gr BTHP's for 1,000 (Gen 1 BC = 0.535). But since Liber's talking about 600 yards, he should be fine with the 168. Slight reduction of recoil, too, with that lighter bullet, which is also kinda nice.

So, Liber, in short, go ahead and buy the 168's and enjoy shooting them. Just be aware of the range limitations with them, that's all. It's like how you wouldn't necessarily use Remington Core-Lokt ammo for long distance, but it's great for putting meat on the table at reasonable hunting distances. Same idea here.

[liber]

So, Liber, in short, go ahead and buy the 168's and enjoy shooting them. Just be aware of the range limitations with them, that's all. It's like how you wouldn't necessarily use Remington Core-Lokt ammo for long distance, but it's great for putting meat on the table at reasonable hunting distances. Same idea here.

I wasn't the one asking originally, but 600 will take care of me.

I was curious though, as I asked in my last post, but where does the 175s and 178s go transonic? In doing a bit more research it seems that might be 1440 for a 175 SMK.

Is that number correct?

[ar15barrels]

I was curious though, as I asked in my last post, but where does the 175s and 178s go transonic?
In doing a bit more research it seems that might be 1440 for a 175 SMK.

Is that number correct?

There is NO single figure.
It depends on the launch velocity and the weather conditions.
Barrel length and load pressure directly effect launch velocity.
Weather conditions effect air density.
It's the air density that slows the bullet down.

[liber]

There is NO single figure.
It depends on the launch velocity and the weather conditions.
Barrel length and load pressure directly effect launch velocity.
Weather conditions effect air density.
It's the air density that slows the bullet down.

Randall,

Missed your other message, but currently using a 16" barrel, and will be looking to upgrade that to a hopefully 24" match barrel, at which point I'll be thinking about going longer distance. Currently shooting 168 SMKs in the 16" barrel. No problems there as I'm shooting mostly 200 yards.

For $#!T$ and giggles, what would the transonic be on 16" and 24" to give me a comparison. Speaking about 175/178 SMK/TMK.

And for clarity, by density you mean moisture in the air, so that in the winter it would be slower? (i.e., foggy or moist days, and possibly humid summer days)

[JMP]

Density is barometric pressure, the largest impact after wind. I'd not bother trying to max out a 16" barrel for distance. You shoot the old 168 SMKs, which are tough to beat at close distances. At 300m, the 168 SMK is hard to beat.

Then, I'd not worry that much about the transonic region in 308 as the distance they cover from Mach 1.2 to Mach 1 is so small that it isn't getting much disturbance. The transonic zone and how a projectile flies is much more important in the longer range cartridge like the 338s where you have a highly efficient projectile that is covering hundreds of meters in transonic territory.

Part of it isn't related to sound, it's simply that bullets like the old 168 SMK has a low BC and poor flight even at the low end of supersonic (it's getting ragged at 1500 fps). That's the problem with 308s with short barrels, they don't start out fast. From 16 to 24", you probably lose 200fps, if not more.

[liber]

I'd not bother trying to max out a 16" barrel for distance.

You don't have to worry about that as I'm not.

I'm just wanting to understand the big picture and how it relates to what I do have.

I appreciate the help you've offered in explaining some of the process, as I do others.

I could just stick my head in the sand over the issue and not worry one way or the other, it's just that I would like to know for my own sake.

Then, I'd not worry that much about the transonic region in 308 as the distance they cover from Mach 1.2 to Mach 1 is so small that it isn't getting much disturbance.

To me it makes sense to understand this before I purchase another barrel. At least I don't see any fault in trying to understand it so I can determine if there might be a better barrel over another to purchase.

The transonic zone and how a projectile flies is much more important in the longer range cartridge like the 338s where you have a highly efficient projectile that is covering hundreds of meters in transonic territory.

Sure, but that doesn't mean it doesn't apply to 308. It certainly does in the sense of the 168 SMK from what others have stated in this thread. Again, thanks for helping explain some of this.