Fixing high ES

[mgunderson]

25 to 30 es in a 308 case isn't bad if it is based on 20 plus shots. Sds under 10 are good enough for 1000 yards. How many rounds on the barrel? Please don't say less than 300. A 308 barrel tends to settle down after 200. Seating depth can help. How far off the lands are you?

 

[Dave Zander]

Listen to the Alex Wheeler interview with Eric Cortina. You might be chasing the wrong rabbit.

 

[Keith Stone]

A lot of good suggestions mentioned above. Since you mentioned a bushing die I am assuming that’s how you are setting your neck tension. I have run into issues using a bushing so I switched to using the bushing to set 2-3thou tension then following with a mandrel to punch the necks back out to 1 thou. Wipe the graphite off the brass but leave it inside the necks for seating bullets

 

[Doom]

Is the 30 ES based on 5 rounds or 10? As for brass weight assuming the same lot, a one grain difference in brass weight is about the equivalent of 0.1 gr of powder, which you can assume is around 6 fps.

You haven't mentioned COAL but you did mention .030" of the lands. These bullets are not sensitive to seating depth so I wouldn't worry about jump and just seat at 2.800" COAL. If this decreases the volume it may improve your ignition.

 

[Doom]

You mentioned changing powder and I would be surprised if the powder/primer combination is an issue but trying 4064 is worth a try.

Can you post the chronograph data for each shot from your tests?

 

[JFrank]

Here’s 21 shots ran past a chrono, it’s easy to see with a simple elimination of three cases I’ve cut the ES in half, those cases also display a difference in weight. It’s still early in my testing to make any absolute claims, but I will continue to sort brass and follow the clues.