Subsonic .308 Load, testing flash hole diameter

I got to shoot my first sub loads, I have not enlarged the primer pocket though. 10.5 of Trail Boss had the best accuracy at 100 so I am going to load those with some fire formed brass. Intend on using them with my can for feral hogs so I do not need moa accuracy.

If I can figure out how to easily enlarge the flash hole I may try a few and compare.


Edit: Not that I consider that I have a flash hole reamer for .080, I will just use that. Not sure another .01 will matter (I really doubt it is worth the time for minute of pig accuracy).

Mrvmax said:

I got to shoot my first sub loads, I have not enlarged the primer pocket though. 10.5 of Trail Boss had the best accuracy at 100 so I am going to load those with some fire formed brass. Intend on using them with my can for feral hogs so I do not need moa accuracy.

If I can figure out how to easily enlarge the flash hole I may try a few and compare.


Edit: Not that I consider that I have a flash hole reamer for .080, I will just use that. Not sure another .01 will matter (I really doubt it is worth the time for minute of pig accuracy).

Click to expand...

.080 will be better than the "normal" primer hole but not amazing. I think it's worth doing.

Just an fyi... when working up subsonic loads don't start when the average daily high starts to decline. I shot the first test at 95 degrees. The lowest charge was pretty close to subsonic but not not quite. So that became the upper end of the next test. That test was shot at 85 degrees The lowest charge was pretty close to subsonic but not quite. Third times a charm right? Nope. I shot that test at a nice 65-70 degrees after a cool front. Nothing I had loaded was subsonic. Close though. I've got one more to test plus some old 900 fps data from last June. I may try to string all of that together in one spreadsheet that has charge and average velocity in it. I have temperature and subsonic velocity chart I can add to the spreadsheet too.

marc357 said:

Another thing that he emphasized was that it was important to fire form your brass to the rifle with full power loads before using the brass to load subsonics. Loading subsonics in virgin brass just doesn't produce enough pressure to fully obturate the brass and he never got good results that way.

Click to expand...

Thanks. Good idea. MOst of these have been new brass that was only fired subsonic. I'll get some of my supersonic fired brass to load.

I broke my .308 in with Tubb Final Finish bullets. It's not max power but it's good enough to form the brass. Then I loaded the brass subsonic from that.

I do all of my chronograph work at my place in east Texas. I get a lot of temp and humidity swings. When you are loading right on the edge of supersonic, you get a lot of "cracks".