THE HANDLOADING BENCH
308 Winchester Rides Again Part 3 By Laurie Holland
guilty of giving a dirtier burn than extruded types. The cause is the absence of the tubular form’s hole up the middle that causes the kernel to burn outwards as well
To Laurie’s surprise, the SRP ‘Palma’ brass version (right) of the 175gn BTLR + H414 ball powder came out on top despite testing in cool conditions.
better in this role as well as being viable in F/TR. Its preferred rifling twist rate runs a bit tighter at 1-12” though.
Ball Powder
That left one more thing to try with ‘Palma’ brass – ball or spherical powders, again using the 175gn Berger BTLR which the barrel obviously liked. Put most 175gn or heavier bullets through a QuickLOAD .308 Win Charge Weight Table run and you’ll find Hodgdon H414 / Winchester 760 (same powder, different bottles) at or near the top of the predicted velocity listing. This is a double-base propellant that’s been around forever, has a slightly faster burning rate than the 4350s and Viht N550, and is well suited to mid-size cartridges because of its density. I usually avoid ball powders as they’ve been traditionally found
as from the outside in. As the ball kernel’s surface area can only reduce as it is consumed, this form produces a ‘regressive’ burning behaviour (high gas production initially reducing as the charge is consumed). To counter this, a thick coating of non-inflammable ‘deterrents’ is used to slow the early-stage burn, but these chemicals are left behind as fouling, usually baked on hard thanks to the double-base propellant’s flame temperatures. Another consequence of heavier surface coatings is greater difficulty in igniting these powders, hence the common advice to use magnum LR primers. Actually, ball propellant technologies and ingredients have moved on a lot over the years, reducing these and other alleged downsides. However, if there is any doubt about the SRP’s ability to light up a heavy charge in .308W, it would likely show up with this powder.
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