Tuning my load for long range

[longrangeprecisionshooter]

I know there has been different threads in the post talking about this topic.
But I didn't find what I am looking for, so I have to ask again:
What I have is a load I am happy with at 100 and 300m for 308win with muzzle velocity between 2650-2700fps depends on bullet used.
I heard that at about 900, the bullet will go into transonic and become unstable which will affect accuracy on paper at 1000.
What I would like to know is, before I travel hours to the 1000 range to shoot, what I could do at home to imporve my load as much as possible for 1000?
Should I be looking for increase the powder charge so more muzzle velocity at 100, then the transonic would happen after the bullet hits paper at 1000?
Or I can stay with my current powder charge(muzzle velocity), just need to adjust the seating depth for 1000? I have a arbor press, so if the powder charge doesn't change, I can seat the bullet high, then use the press to seat the bullet deeper as needed later at the range.

Thank you.

 

[piie]

Have you played with some ballistic calculators yet? Are you sure you have the correct bullet for the job? A higher BC bullet will have the same effect - ie, carry more speed, but typically, require more twist to stabilize.

 

[Capt. Oblivious]

What bullet are you shooting

 

[Walt Schmidlin]

With most 155gr bullets a muzzle velocity of 3000fps is necessary for accuracy at 1000yds.

 

[JFrank]

I know there has been different threads in the post talking about this topic.
But I didn't find what I am looking for, so I have to ask again:
What I have is a load I am happy with at 100 and 300m for 308win with muzzle velocity between 2650-2700fps depends on bullet used.
I heard that at about 900, the bullet will go into transonic and become unstable which will affect accuracy on paper at 1000.
What I would like to know is, before I travel hours to the 1000 range to shoot, what I could do at home to imporve my load as much as possible for 1000?
Should I be looking for increase the powder charge so more muzzle velocity at 100, then the transonic would happen after the bullet hits paper at 1000?
Or I can stay with my current powder charge(muzzle velocity), just need to adjust the seating depth for 1000? I have a arbor press, so if the powder charge doesn't change, I can seat the bullet high, then use the press to seat the bullet deeper as needed later at the range.

Thank you.

If possible take a ladder test with you to confirm charge weight, if not you might get lucky or may take your lumps

 

[Beiruty]

What bullets are you shooting?
Are you measuring the MV with Labradar/Magneeto?
What is the SD of the MV?
What do your groups look like? Please post some photos

 

[Dkk37058]

Sierra 168gr matchings will go subsonic around 800 to 900 yards and will give you trouble.
The 175 and 169 matchings will work for 1000.
The 169gr matchings have been out a couple of years and are advertised as made especially for 1000yrd shooters.
I’ve used these and they work good

 

[RustyInBend]

I'd try three things ...
Thing 1: Seek the highest velocity that has no pressure signs (heavy bolt is usually first) and tight groups.
Thing 2: Use a bullet on the lighter side to take advantage of additional velocity.
Thing 3: Use a ballistic calculator (there are lots of them) to estimate transonic flight.
The right combination of bullet and charge should keep a 308-Win supersonic to 1000 yards.
Oh ... Thing 4 ... Buy a 300-Norma so you don't have to care about your bullet at 1000 yards.

 

[Doom]

Depending on elevation and temperature you will probably need the 175SMKor the 169 SMK as a minimum. The velocity needed will depend on this also. Use JBM Ballistics to determine what you will need.

The 155's are acceptable but you usually need >26" barrel to get the velocity unless you are up in elevation.

 

[ebb]

The 168 version of Fed GMM don't make it to 1000 before going subsonic down here at sea level. It may be different where the OP is but without a bunch more information there is no way to tell.

 

[cmysix]

Palma shooters love the berger "full bore" 155.5 grain in .308 out to 1000

 

[coford]

Shoot heavy bullets as fast as you reasonably can and you will be fine. If you go 155's push them to 3000 fps. I68's don't cut it. Heavier is better. I have seen so many people over the years be frustrated at how stuff falls apart beyond 900 with a .308.

 

[David Christian]

@longrangeprecisionshooter, what bullet are you using? I am trying to back into what you are using and just played with my ballistics app. In a .308 a 215 grain bullet shoots around your 2,650 speed. If that is your case, it does not go transonic until past 1,400 yards, assuming sea level.

 

[Ned Ludd]

The BC of the bullet actually used by the OP is key here. Until/unless the OP comments on which bullet was used, the rest is speculation. F-TR .308 Win shooters with 30" barrels typically achieve somewhere within the following velocity ranges at safe operating pressures for tuned loads with different bullet weights using SRP brass and powders somewhere around the burn rate of Varget:

155s: 2950 to 3000 fps
168s: 2850 to 2900 fps
185s: 2725 to 2750 fps
200s: 2630 to 2680 fps
208s: 2570 to 2620 fps
215s: 2520 to 2570 fps

With only one exception that I am aware of, all of these loads will reach 1000 yd prior to going trans-sonic when using a sufficient twist rate; the one exception being the SMK168, which suffers from an excessively steep boattail angle that generates dynamic instability. Other 168s having a typical boattail angle of ~7-8 degrees do not suffer from this issue. It is also worth noting that trans-sonic behavior is a bullet-specific phenomenon. Some are better than others. Many of the bullets commonly-used by F-TR shooters in the above weight classes seem to fare reasonably well if they're just starting to approach trans-sonic, as some of the above loads/velocities will be at 1000 yd. However, such loads are typically not developed such that they're going to be well into the trans-sonic region or sub-sonic, at 1000 yd, for obvious reasons.

 

[Sixgun]

I know there has been different threads in the post talking about this topic.
But I didn't find what I am looking for, so I have to ask again:
What I have is a load I am happy with at 100 and 300m for 308win with muzzle velocity between 2650-2700fps depends on bullet used.
I heard that at about 900, the bullet will go into transonic and become unstable which will affect accuracy on paper at 1000.
What I would like to know is, before I travel hours to the 1000 range to shoot, what I could do at home to imporve my load as much as possible for 1000?
Should I be looking for increase the powder charge so more muzzle velocity at 100, then the transonic would happen after the bullet hits paper at 1000?
Or I can stay with my current powder charge(muzzle velocity), just need to adjust the seating depth for 1000? I have a arbor press, so if the powder charge doesn't change, I can seat the bullet high, then use the press to seat the bullet deeper as needed later at the range.

Thank you.

Serria 175 TMK's fly very well out of a .308. 44gr. of Varget gave me 2750 with no pressure signs....of course work up to it.

 

[Sixgun]

Serria 175 TMK's fly very well out of a .308. 44gr. of Varget gave me 2750 with no pressure signs....of course work up to it.

...excellent at 1000y

 

[Capt. Oblivious]

Maybe the OP busy doing a speed ladder to find a node