<span style="font-weight: bold">My question is for other people shooting 308's with 168 and heavier bullets using IMR 8208 XBR: What are you getting for ES/SD numbers and what load are you running? </span>
I've been using IMR8208 for a while now with 155 grain bullets in my semi auto 308 and have had great results. Better than anything else I've tried. I've had great velocity, SUPERB accuracy, great ES/SD numbers and nothing in general to complain about. I've taken the 155.5 Fullbore out to 700 yards with good (for a 16.5" AR) results.
Recently decided to switch to 168 grain Berger Classic Hunters (the new SAAMI compliant hybrid)for a little better wind resistance and hunting ability. With these bullets, my ES/SD numbers are much higher with 8208 than Varget and I'm working on ways to get them down.
Varget ES = 26 / SD = 10
8208 ES = 46 / SD = 17
The above numbers are with the same annealed/sorted Winchester brass and CCI Br-2 primers on the same day, velocities derived from 10 shots each over an Oehler 35P, 10 ft from the muzzle.
I'm thinking IMR8208 may just be too fast and have too little case fill to get the numbers down to where they are with Varget with 168's. I tried switching to Winchester LR (hotter) primer instead of the BR-2's and the deviations got much worse, ES=77/SD=33
Not sure where to go from here, the obvious answer would be to just use Varget but I don't want to because I can't run the high node in my rifle as it beats everything up too much. So I'd have to live with better vertical dispersion at distance, but 100 FPS less velocity than I can get with 8208, not a huge deal, but 8208 is easier to throw and I have 15 lbs more of it than Varget.
For this testing all loads were hand-weighed. If there's any way for me to get 8208 up to snuff with this combo that's absolutely my first choice and I don't mind putting in a little more work to get there. Seating depth may help tune up 8208 some I'm hoping, but further development will have to wait a couple of weeks while I wait on a new extractor for my rifle.
So I have time to think about what my next move will be, give up on 8208 with these bullets as a lost cause or continue burning components chasing down ES numbers. So far I haven't been able to shoot this work up past 200 yards, but I will be shooting steel out to 700 yards (maybe 800 if we clear the lane further at our lease).
I'm wondering if my experience is an anomally and I should try adding more powder or if I'm correct in my thinking that 8208 is too fast for this combo. I'm just about maxed already at 42.8 grains of 8208, half a grain below Hodgdon max and getting 2530 FPS out of a 16.5" barrel in Winchester brass but I can push it up a little maybe, haven't seen any pressure signs so far and they've been very apparent with this rifle when they were present in the past.
Have I missed anything that jumps out as obvious to anyone else?
I've been using IMR8208 for a while now with 155 grain bullets in my semi auto 308 and have had great results. Better than anything else I've tried. I've had great velocity, SUPERB accuracy, great ES/SD numbers and nothing in general to complain about. I've taken the 155.5 Fullbore out to 700 yards with good (for a 16.5" AR) results.
Recently decided to switch to 168 grain Berger Classic Hunters (the new SAAMI compliant hybrid)for a little better wind resistance and hunting ability. With these bullets, my ES/SD numbers are much higher with 8208 than Varget and I'm working on ways to get them down.
Varget ES = 26 / SD = 10
8208 ES = 46 / SD = 17
The above numbers are with the same annealed/sorted Winchester brass and CCI Br-2 primers on the same day, velocities derived from 10 shots each over an Oehler 35P, 10 ft from the muzzle.
I'm thinking IMR8208 may just be too fast and have too little case fill to get the numbers down to where they are with Varget with 168's. I tried switching to Winchester LR (hotter) primer instead of the BR-2's and the deviations got much worse, ES=77/SD=33
Not sure where to go from here, the obvious answer would be to just use Varget but I don't want to because I can't run the high node in my rifle as it beats everything up too much. So I'd have to live with better vertical dispersion at distance, but 100 FPS less velocity than I can get with 8208, not a huge deal, but 8208 is easier to throw and I have 15 lbs more of it than Varget.
For this testing all loads were hand-weighed. If there's any way for me to get 8208 up to snuff with this combo that's absolutely my first choice and I don't mind putting in a little more work to get there. Seating depth may help tune up 8208 some I'm hoping, but further development will have to wait a couple of weeks while I wait on a new extractor for my rifle.
So I have time to think about what my next move will be, give up on 8208 with these bullets as a lost cause or continue burning components chasing down ES numbers. So far I haven't been able to shoot this work up past 200 yards, but I will be shooting steel out to 700 yards (maybe 800 if we clear the lane further at our lease).
I'm wondering if my experience is an anomally and I should try adding more powder or if I'm correct in my thinking that 8208 is too fast for this combo. I'm just about maxed already at 42.8 grains of 8208, half a grain below Hodgdon max and getting 2530 FPS out of a 16.5" barrel in Winchester brass but I can push it up a little maybe, haven't seen any pressure signs so far and they've been very apparent with this rifle when they were present in the past.
Have I missed anything that jumps out as obvious to anyone else?
