No. 4 7.62 Long Range Load

Thanks for this post, I intend to use it as a reference for some experimentation with some 168gr PPU in my No.4 along with other PPU's in 147gr & 150gr.

The 168gr I have previously dismissed as rubbish in my Accuracy International due to a wide variation of bullet weights. 

Have now sorted them in lots corresponding to their weights. 

The TMK was designed to overcome this limitation and produce supersonic velocities in the .308 Win out to 1000 yards.  It’s a significantly longer bullet with secant ogive and shallow boattail angle like the 175 SMK which adds up to a significantly higher Ballistic Coefficient and better retention of down range velocity, perfect for what I’m looking for. 

I weighed 10 of the 168 TMKs at random and they are remarkably consistent, 167.9 to 168.1 grains, 7/10 were 168.0 grains. 

168 SMK on left, 168 TMK on right.  According to Sierra, load data for the SMK can be used for the TMK, but I have to wonder if that additional length of bullet stuffed in the case when seated to magazine length doesn’t increase pressures.  

Zed,

I wasn’t overly impressed with how the 155 Palma match bullet shot, as compared to the 175 TMK. At short to Medium range tho, it was quite good.  You might want to load up some at the .308 Win published Starting Load for N140 or 202 and perhaps work up to the mid range of the tables.

I looked up N140 on the Vihtavuori website for the 155 Palma but they don’t give pressures.  Their starting load velocity is quite low, 2354 fps at 37 grains, I would probably start at 38 grains and a max of 41-42.  If you’re not shooting past 600, 40 grains may be sufficient.  Assuming you’re using commercial .308 brass and standard LR primers. 

I’m planning on going back to the Spencer range on Tuesday.  Going to be pretty cool, 19 deg F in the morning, warming up to 49 deg F in the afternoon.  This is another significant variable to deal with when making a powder selection for your long range loads and predicting down range velocity and rear sight elevation settings.  Some powders are notoriously affected by temperature changes affecting muzzle velocity (and consequently, down range velocity and trajectory). If you live in an area of fairly constant temps, no big deal, but here, I could be shooting in temps down in the 20’s F in winter and 90 deg F in summer.  Some powders will create a muzzle velocity difference of 100 fps or more for this large of temperature difference.  This can be very frustrating when shooting in matches where No sighter shots are allowed.  

One of the reasons I use Varget is that it is a very temp stable powder.  0.2 to 0.4 fps change per deg F based on test data.  The Strelok program allows you to enter the muzzle velocity as a function of ambient  temperature.  

All of this let’s you get your first shots on the target, and for me, more importantly have the confidence that my load will work the sound sensors at 1000 yds based on the actual weather conditions at the range.  I can run the app on my phone to get real time updates in sight settings and velocity. Pretty cool program.