Raffaella Gaudini re .308 Winchester

I am currently reloading ammunition for my Remington 700 PSS rifle, chambered in 308W. It is in unmodified "out of the box" format and the usual distance I am shooting is 300 metres. I have found my "benchrest load" with 41 Grains N140 or 41.5 N150 and 168 SMK. I don't have a chronograph but it appears that my rifle likes low powder charge weights for small groups. I would like to test some rounds for target shooting at 600 yards. Could you suggest to me some reloading data suitable for this distance: I think my present cartridge could be too slow?

I would like more velocity but accuracy comes first. Thank you in advance.
Raffaella Gaudina Italy

It's not uncommon to obtain very good accuracy with mild loads such as that quoted, especially in factory rifles. There are two factors potentially causing this occurrence: action/barrel harmonics ‘sweet spots'; the fit of the locking lugs in the action. If it is purely as a result of the first factor, increasing the load enough often sees pressures and velocities reach the next ‘sweet spot' that may be 150 or even 200 fps higher giving good accuracy but more usable MVs. The other factor is one that normally only applies to factory rifles and sees the lugs bear unevenly on the receiver, in extreme cases one lug does all the work. As pressures rise, this unevenness can increase and factors such as the less-engaged lug being pushed into hard contact with the receiver in an inconsistent manner will cause ‘fliers' due to changes in the action and barrel harmonics pattern. Also, in two-lug Mauser system actions such as the Remington 700 with the lugs at the 6 and 12 o'clock positions when the bolt is locked and cocked plus an action that has a big hole in the top and bottom surfaces of the receiver, this layout can see accuracy deteriorate at maximum allowed pressures due to excessive action flexing.

The load quoted of 41.0gn N140 with a 168gn Sierra is mild. QuickLOAD estimates 2,560 fps for it at around 45,000 psi, while 2,750 fps or a little more should be possible with this weight of bullet from a 26" barrel. The N150 load is even ‘softer' with the estimates running at under 2,450 fps / 37,000 psi. These loads are usable at 600yd and easily remain supersonic. The N140 MV is very close to the old US Service Rifle loads for the .30-06 M1 Garand and later 7.62mm M14/M1A type semi-auto rifles using this bullet and IMR-4064 or 4895, and able to stay within a 1-MOA X-ring at 600yd from an expert shot using a tuned rifle. It is not the best 600yd bullet available nowadays however. You have a choice of a 155gn Palma / Fullbore Rifle bullet at a higher MV, or going to something a bit heavier in the 175-185gn weight range and attempt to get similar MVs to those you're currently (probably) producing from the 168.

The bullets that I would suggest trying are the new-model 155gn Sierra Palma MK (No. 2156) which is much more efficient ballistically than the older model (2155), or its 155.5gn Berger Target Match BT FULLBORE competitor. Start at around 42gn N140 and work up carefully in 0.5gn steps to somewhere between 45 and 46gn, or even a bit more to see how accuracy does at these levels.

The other two bullets I would suggest trying are the 175gn Sierra MK and the new Berger 185gn Target Match BT Long-Range, both tangent ogive and therefore ‘jump tolerant'. Both are capable of very good accuracy at 2,450-2,600 fps in a rifle such as yours. The Berger is one of the most ballistically efficient bullets on the market and has a higher G7 BC than equivalent weight VLD models. For these bullets I'd suggest N150 or N550 if you are using Vihtavuori powders rather than N140 or 540. Hodgdon VarGet and Alliant Reloder 15 also work well in many rifles. I would try loads in the 42-44gn range initially with VarGet, Re15 and N150, and if pressure signs are acceptable go a bit higher in smaller steps (0.3gn). Viht N550 should be loaded a bit more heavily, say 43-45gn or even up to 46gn if pressure signs remain OK. Depending on the brass you are using and seating depths, you'll likely find you're getting into compressed loads at these upper levels. (I should mention that I am assuming you are using 308W commercial brass such as Norma, Lapua or Winchester. If you're using milspec 7.62mm cases, such as MEN, then you must drop charges by up to 2gn.)

The following list shows how these potential loads look ballistically:
Bullet               V0             V600         D600 (1)              D600(2)
168gn SMK       2,560 fps   1,480 fps   39.06" (154mm)   9.54 (38mm)
155gn New SMK 2,800 fps   1,727 fps   31.09" (122mm)   7.6" (30mm)
175gn SMK       2,600 fps   1,609 fps   33.12" (130mm)   8.1" (32mm)
185gn Berger    2,450 fps   1,625 fps   29.6" (116mm)    7.2" (28mm)
BT L-R
185gn Berger   2,550 fps   1,706 fps   27.8" (109mm)    6.8" (27mm)
BT L-R
V figures = MV and 600yd in fps
D values = wind drift at 600yd. D600(1) is a straightforward 10mph crosswind at 3 o'clock. D600(2) is 2.5mph at between 4 and 5 o'clock, to represent the effect on the bullet strike of a missed (i.e. unnoticed and not adjusted for) quite modest change in wind speed and/or direction.

It can be seen that even at a modest 2,450 fps MV, the 185gn Berger gives a very useful reduction in wind-drift at this range. Hodgdon VarGet and Viht N150 usually give small velocity spreads with these bullets in my experience providing good quality brass is used, and while this has little benefit on the target at 200/300yd, it starts to become valuable at 600yd, with large spreads causing some vertical dispersion on the target at this range.

The usual caveats about starting at low loads, working up in small (0.5gn at the most) steps and looking for over-pressure signs apply, especially as some of the load suggestions exceed those in the manufacturers' loads tables, Vihtavuori in particular being very conservative with its N140 data.

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