Thread: Light Loads for a .308W.

I started a bunch of testing of Robert Walker's 308 151gn Gas Checked Cast HP in my Interarms 308 and my Marlin 336 30-30 which has been interrupted by Covid and Surgery.

I used Lyman data for reduced loads with 3031. I've not got to using them on game yet but there is plenty of evidence of their effectiveness there.

With the 308 the data showed a Start Load of 27.0gn powder for 1767 fps and a max of 42gn Compressed for 2810 fps. The data was for a Lyman #311466 from Lyman Cast Bullet Handbook 3rd Ed, p 185.

I stopped my incremental Load Test at 37.0 gn as accuracy started to go off with 4 shots at 2402, 2305, 2331 and 2233 fps and the load started to feel rather hot. Quite a spread and I was not really looking for that high a velocity from Cast.

Target was at 50m, Primer was Fed 210 LRP and brass was 7.62 military. Barrel is 22.5" Suppressed.

My increments were coarse at 1.0gn per step. While there was reasonable hunting level grouping at several load levels the best was a node at 34.0gn with shots giving 2246, 2094, 2081, 2075 fps and another at 28.0gn with shots at 1609, 1646, 1606, 1607 fps. The latter was by far the best group. I made 50 of these for an NZDA hunter training shoot at 100 and 200m. Bearing in mind that I am a complete novice at NZDA shoots in particular and that both the rifle and the load are fairly new to me I was pretty happy to be in the kill zone on all but a couple of my shots.

Subsequently I ran incremental tests with Trailboss and also tested "The Load" using IMI Nobel 78 Shotgun powder instead of Red Dot. Primer was a Fiocchi LRP

the best result I had with the Nobel 78 was at 12.0gn. Higher than that I started experiencing occasional heavy bolt lift. At 12 gns I recorded 1598, 1592, 1578, 1581 fps. This was by far the best group I have achieved with these projectiles, any powder. This makes a very economic powder choice. My lowest charge in this run was 7.5gn for 1204, 1241, 1207, 1225 fps and good grouping.

With Trailboss I was looking for subsonic but 151gn I think is probably a tad too light a projectile for really effective subs in 308. 8.5gn gave me results that were on the cusp - 1176, 1166, 1194, 1188, 1166 fps. This was a very accurate load at 50m but some went supersonic about the same as .22 hi velocity.

At 6.5gn I had a tight clustered group of 3 with one outlier and an average of 1006fps, at 7gn an average of 1044 with clear horizontal stringing

My perceived difference in sound between suppressed supersonic with 8.5gn and complete subsonic with 6.5 did not seem that great.

I think in a bush hunting scenario I'll stick with the better hitting power of a 151gn projectile in the 15-1600 fps band that is also grouping well.