Driftertank
Member
Just wanted to share some observations from a test I did yesterday with some 160gr Nosler Accubonds in my Bergara B-14 Ridge rifle.
The internet has a lot of back and forth with jump info for these rounds. I decided to do a relatively controlled test, using a known combination of case, primer, and powder, and varying only the jump dimension. I used an intermediate load of H1000 in Hornady brass with Fed 215GMM primers. I did not change charge weight throughout the test, so the variation in case free volume may effect pressure and velocity separately from the effects of jump length, but it was my belief that altering the powder charge would introduce more variables and reduce duplicability.
Measured COAL to lands in my rifle was 3.364"
Prior tests with jump dimensions between .020" and .040" were underwhelming at best, so I decided to look into longer COALs.
Ammunition was loaded in pairs (I'm running short of bullets lately) at .020" intervals, between 3.220" and 3.300"
Testing was done at 200 yards. Center bullseye hold was used in every case. Given the small sample sizes, I was only looking for trends.
Initial conclusions seem to suggest that, for this cartridge/rifle/bullet combination, the 160 AB's are happiest at around .080" or .140" off the lands, with the longer jump possibly being more forgiving, based on the fact that the .120" group shows smaller sizes than the .060" and .100" groups. I didn't go any shorter than 3.220" COAL because the ogive is getting quite close to the case mouth at that OAL.
I have loaded another couple small sample groups worth of ammunition at the 3.220" length and plan to revisit this next time I have a day off to get back to the range.
Sorry for the small sample sizes, I'm trying to get a load put together for my new hunting rifle and still have enough heads to hunt with until more 160 AB's materialize again. Still, I thought my relatively empirical data might be useful to someone trying to get these to shoot.
The internet has a lot of back and forth with jump info for these rounds. I decided to do a relatively controlled test, using a known combination of case, primer, and powder, and varying only the jump dimension. I used an intermediate load of H1000 in Hornady brass with Fed 215GMM primers. I did not change charge weight throughout the test, so the variation in case free volume may effect pressure and velocity separately from the effects of jump length, but it was my belief that altering the powder charge would introduce more variables and reduce duplicability.
Measured COAL to lands in my rifle was 3.364"
Prior tests with jump dimensions between .020" and .040" were underwhelming at best, so I decided to look into longer COALs.
Ammunition was loaded in pairs (I'm running short of bullets lately) at .020" intervals, between 3.220" and 3.300"
Testing was done at 200 yards. Center bullseye hold was used in every case. Given the small sample sizes, I was only looking for trends.
Initial conclusions seem to suggest that, for this cartridge/rifle/bullet combination, the 160 AB's are happiest at around .080" or .140" off the lands, with the longer jump possibly being more forgiving, based on the fact that the .120" group shows smaller sizes than the .060" and .100" groups. I didn't go any shorter than 3.220" COAL because the ogive is getting quite close to the case mouth at that OAL.
I have loaded another couple small sample groups worth of ammunition at the 3.220" length and plan to revisit this next time I have a day off to get back to the range.
Sorry for the small sample sizes, I'm trying to get a load put together for my new hunting rifle and still have enough heads to hunt with until more 160 AB's materialize again. Still, I thought my relatively empirical data might be useful to someone trying to get these to shoot.