help me understand .30 168's at 1000 yds.

[3035Odell]

I have read lots of places where the 168 Sierra does funky stuff when it goes tran-sonic just short of 1000 yds. and just read in another thread that they are not the best choice for even 600 yds. I have shot nosler cc 168's at mid range matches to 600 yds. Never did particularly well but I think it is more me. Is the issue specific to Sierra's boat tail shape or are all 168's turds at longer ranges?
I can't get my head around why it would be just the 168 grn. weight when 155 palmas and 175 mk's work in the same guns?

 

[mac86951]

Shape of bullet is the problem. The shape (I believe the boat tail I specific) causes instability in the transition from super to sun sonic on the 168s. The 155s are launched such that they retain supersonic at 1000y (ie 32" barrel); the 175s behave better in the transition zone.

The 168s should be fine if they are supersonic at 1000y; don't know if anyone is using them in a long barrel. Palma restricts weight to 155.5 if I'm not mistaken.

-Mac

 

[asyoung]

As I understand it, the Sierra 168 was single purpose designed to be very accurate out to 300 meters for 300 meter international rifle shooting. It does that very well and is forgiving in a lot of different rifles. But it was never intended to work well at 1,000 yards. The 155's and 175's were designed to work at 1,000.
The 168's also work fine at 600, but they will be moved more by wind than 155's or 175's but it takes a fairly decent shooter for it to be an issue.

 

[dcali]

It's not the weight. It's the nature of the old Sierra International bullet design. I believe it was the boat tail angle that caused dynamic stability issues in the transonic region.

 

[Comrade Terry]

168 TMKs work just fine for me at 600. They're okay at 1,000 but I prefer the 175s for that (wind).

 

[3035Odell]

Thanks very much. I asked the right people

 

[swd]

They leave a perfect silhouette of a bullet in the target as they tumble through. I've seen it many times....

 

[shoot4fun]

I've been at 1000 yard matches where someone humiliated us with a 168 grain bullet but it wasn't Sierra SMK. With the proper load I think some of them can do well out to 1000 yards. If you can have 30 to 32" barrels like F-Class then you should be able to get the Berger to shoot well but it seems the 155's are a better choice. I shoot a match that holds barrels to 26" or less and 185 Hybrids pushed hard by 2000-MR have served me pretty well.

 

[XTR]

It's not the 168 weight, it is the angle of the boat tail on the 168SMK. Other 168s can be fine.

 

[Erud]

Shape of bullet is the problem. The shape (I believe the boat tail I specific) causes instability in the transition from super to sun sonic on the 168s. The 155s are launched such that they retain supersonic at 1000y (ie 32" barrel); the 175s behave better in the transition zone.

The 168s should be fine if they are supersonic at 1000y; don't know if anyone is using them in a long barrel. Palma restricts weight to 155.5 if I'm not mistaken.

-Mac

Palma in the USA has no bullet weight restriction, but it should.

 

[mac86951]

Palma in the USA has no bullet weight restriction, but it should.

Ahh, my bad. Thanks for clarification.

 

[Turbulent Turtle]

It's not the 168 weight, it is the angle of the boat tail on the 168SMK. Other 168s can be fine.

Wade is correct. The problem with the original 168SMK is that the boat tail angle is too sharp to get the reduction in the drag and therefore goes subsonic faster than it really should due to the increased drag. The shape of the bullet is such that when it goes transonic it spins around the center of mass and that center is towards the back of the bullet so it spins out.

Sierra corrected (reduced) the boat tail angle in the 168TMK and that bullet now gets the benefits from the reduction in drag provided by the boat tail and stays supersonic to 1000 yards or more.

Some other 168s have that boat tail issue also, but most others do not.

 

[USMCDOC]

As I understand it, the Sierra 168 was single purpose designed to be very accurate out to 300 meters for 300 meter international rifle shooting.

Correct!

 

[Liven The Dream]

I have read lots of places where the 168 Sierra does funky stuff when it goes tran-sonic just short of 1000 yds. and just read in another thread that they are not the best choice for even 600 yds. I have shot nosler cc 168's at mid range matches to 600 yds. Never did particularly well but I think it is more me. Is the issue specific to Sierra's boat tail shape or are all 168's turds at longer ranges?
I can't get my head around why it would be just the 168 grn. weight when 155 palmas and 175 mk's work in the same guns?

The 168 is a 600 yard Bullet .... It was for national match course of fire. ( Berger 168 HB will make it to 1000)
I shoot Palma , 1000 prone and F/TR . The saying with us is you don't let friends shoot 168's at 1000 !!!!!!
168's up to 600 ... In 155's 2156 Sierra and Berger 155.5 are most common. 155's need to run at 2984 to 3030 range.
I run 32" barrels 1-13 and 1-12 left twist , 95 Palma Chamber the 1-12 LT seem a little better.

 

[Laurie]

As others have said, it's a design not a weight issue. Sierra's 168gn 'International' was its first match design (specially introduced for 300-metre ISU competition in the early 1960s) and was a huge success, especially when it was found to work out to 600 yards in Service Rifle / XTC in tuned-up M1 Garands, later M1A / M14 rifles. Shooting teams set up multiple presses in a row on a bench to take issue GI 173gn 30-06 rounds, break the neck-bullet seal, pull the arsenal bullet, reseat a 168gn SMK - so-called 'Mexican Reloads' from the Mexican wave movement passing rounds / demilled cases down the line.

Other manufacturers put their own versions into production to have a competitive product - the Speer 'Gold Match', Nosler 'Custom Competition', Hornady 'National Match'. Although not copies of the 168 SMK, they all used the same sharp (13-15 degree) tail section angles and short boat-tail sections. Bryan Litz says that once the tail angle gets much into double figures the airflow stops following the bullet shape (which is how a boat-tail design works by reducing the bullet base diameter and hence tail-drag) and creating a turbulent airflow behind the shank / tail junction. This increases drag hence reduces the effective BC, and in some ambient conditions, the rear end turbulence will destabilise the bullet as it drops into transonic then subsonic speeds. The word got around that 30-cal 168s didn't work at long ranges in an era where the 30-06 then 308 Win were the most widely used cartridges in competition, hence the belief that there is something inherently 'wrong' with this weight. Some 30-cal AMAXs were similarly blighted and not just the 168gn model.

Berger has never made a HPBT design in any calibre or weight with 12-deg + BT angles, so all 168gn .30 Bergers are true long-range designs in this respect irrespective of age, and the latest model, the 168gn Hybrid is a superb long-range performer with an optimal 7-degree tail angle. Recent introductions from other manufacturers have seen shallow tail angles designed in.