Steyr SSG PII: Bullet for 1,000 yards?

[maximus otter]

I’ve recently picked up a nice SSG with a barrel slightly shortened to accept a muzzle brake.

I reload using only Vihtavuori N133 / N140 / N160 powders, Lapua brass and CCI benchrest primers.

Vihtavuori’s maximum book load for my 167 Scenars is 44 grains of N140. I’ve just done a ten-round test in 0.2 grain increments, topping out at 44.2 grains ( naughty! ). This gave me a Magnetospeed MV of 2,654 fps. Strelok Pro indicates that this combo will go transonic at only 850 yards.

Even worse, there’s a nice node at the slightly lower charge of 43.8 / 2,593 fps. ( Trans at 800 yards.)

My question: Should l:

a) Ignore Vihtavuori’s manual & go higher than their recommended max load of N140, or;

b) Select a different ( heavier? ) bullet, e.g. a 175 grain?

c) lgnore the issue? (l only shoot at 1,000 a couple of times per year.)

d) Some other solution entirely, to get me a bit closer to 1,000?
 

maximus otter

[Popsbengo]

I'm assuming .308 calibre.  If your twist rate is fast enough (1:11 works for me) I'd try 185gr Berger Juggernaut with N150.  The excellent BC will help get to 1000yds with decent velocity.

I'd avoid going over 44gr N140, a slower powder may work better for your heavier bullets.

[20series]

Hi mate, 

When we were working on Deb's 308 loads we comfortably had SMK 175's going at 2660 with 41gns Vit150 which gives the following Strelok info

Alan

[maximus otter]

28 minutes ago, 20series said:

Hi mate, 

When we were working on Deb's 308 loads we comfortably had SMK 175's going at 2660 with 41gns Vit150 which gives the following Strelok info

Alan

 

Cheers pal, useful info.

l was hoping to be able to use my current powders, and not have to auction my last kidney for another kilo of Viht…

maximus otter

[Laurie]

32 minutes ago, 20series said:

SMK 175's going at 2660 with 41gns Vit150 which gives the following Strelok info

 

That must be using Sierra's G1 BCs. The average long-range G7 BC for this bullet is 0.243. Input that at 2,660 in a 'standard ballistic environment' (59-deg F 29.92-inches mercury) and the 1,000 yard retained speed is calculated to be 1,123 fps, ie just subsonic, not 1,247 fps. 

In practice, with a normal range of MVs and variations between individual bullets' BCs, you get a very poor situation of some bullets super, and others sub-sonic on the target with this outcome which is ruinous to grouping and consistency. (I found this out the hard way 12 or 13 years ago in Year 1 of FTR in the UK shooting this exact combination on the Glen Tilt range at Blair Athol in a match in cold, difficult-headwind conditions despite the range being >1,000 ft ASL.) On  ShotMarker and similar e-targets that use the supersonic 'crack' to determine the location of the shot-fall through microphones, many shots wouldn't produce a reading too. (Kongsberg and Intargo designs do work though as they use vibrations in neoprene screens, not sound.)

For an occasional 1,000 yard outing, the better 155s are as good as anything in a rifle like this, and moreover suit N140 extremely well. The older 155gn Sierra MK (#2155) is the bullet loaded in the NRA's contract 308 ammo for 'Target Rifle' and continues to perform extremely well at 1,000 (and beyond) even though it'll be subsonic in many rifles. The Berger 155.5gn LRBT is even better, but is an expensive bullet and hard to get hold of most of the time (not that SMKs are in good supply either for that matter).  

[Catch-22]

I always found 155gn Scenars and N140 to be a good solid combination in .308w.

[maximus otter]

Thanks to all. l might experiment with 155s by Lapua or Berger.

maximus otter