For all the other reloading newbs out there that are buying used brass or necking down brass to save a little money... To avoid lots of headaches and improve overall safety in your process, it's crucial that you get a head space comparator for your cartridge. I know, I know, this is a "duh, you idiot" from the veteran reloaders, so please be gentle. However, as a self-taught guy, I've been learning a lot with my 7-08 and want to take a minute to share and help others avoid the same.
The brass I'm using for the 7-08 includes a few hundred .308 cases from a couple different rifles that I've necked down with my Hornady FL die. I also recently purchased some once-fired Alpha 7-08 brass from another member. In the beginning, I assumed by running all the brass through the FL die at standard SAAMI spec. (shell holder touching the bottom of the die) the cases would all be sized appropriately and ready to load. However, I quickly ran into issues with random cases being hard or next to impossible to chamber. I measured OAL and the cases were all +/- a few thousandths and inside max length spec., so no issue there, but what I didn't fully comprehend was the differnce in the base to shoulder measurement, because hey, I FL sized everything and it should be okay.
To make an already long post short(er), when I got a head space comparator attached to my calipers, I quickly understood my faulty assumptions. The fired cases that had no issues chambering measured 1.623 from the base to the shoulder after firing. I verified this with necked down brass as well as a handful of new pieces of Alpha brass that were sized/fired. So, subtracting a couple thousandths for bump, the ideal base to shoulder measurement for this rifle's chamber should be around 1.621. At this point my mild OCD kicked in, and I spent the next 90 minutes or so measuring every piece of brass, and the results explained a lot.
It turns out that after SAAMI FL sizing all of my brass, the head space measurement varied from 1.617-1.629. About 50% of the brass ranged from 1.617-1.622, and the remaining 50% was 1.625-1.629. For an additional confirmation, I tried chambering random cases from each cohort, and what do you know, the former chambered easily and the latter took mild to extra effort or wouldn't chamber at all, even after FL sizing. As a result, with a little trial and error adjusting the FL die and measuring with the comparator, I found that screwing the die about 1/4 turn or so deeper gets me at or under 1.621 for the pieces in the 1.625-1.629 range.
The next step is to lube and re-size all of the 1.625-1.629 cases and measure to make sure they're inside spec. for this rifle. They're obviously not all going to be perfect, but as long as they're under 1.622, they should chamber without issues. After firing, in the future I'll measure again to confirm they're 1.623ish in length, and then adjust the FL die appropriately for .002 bump.
To summarize, if you're buying fired brass or necking down brass from other rifles, make sure you are measuring not only OAL, but most importantly, the base to shoulder head space. This will eliminate issues chambering your reloaded ammo and hopefully mitigate waste and rework at the bench.
The brass I'm using for the 7-08 includes a few hundred .308 cases from a couple different rifles that I've necked down with my Hornady FL die. I also recently purchased some once-fired Alpha 7-08 brass from another member. In the beginning, I assumed by running all the brass through the FL die at standard SAAMI spec. (shell holder touching the bottom of the die) the cases would all be sized appropriately and ready to load. However, I quickly ran into issues with random cases being hard or next to impossible to chamber. I measured OAL and the cases were all +/- a few thousandths and inside max length spec., so no issue there, but what I didn't fully comprehend was the differnce in the base to shoulder measurement, because hey, I FL sized everything and it should be okay.
To make an already long post short(er), when I got a head space comparator attached to my calipers, I quickly understood my faulty assumptions. The fired cases that had no issues chambering measured 1.623 from the base to the shoulder after firing. I verified this with necked down brass as well as a handful of new pieces of Alpha brass that were sized/fired. So, subtracting a couple thousandths for bump, the ideal base to shoulder measurement for this rifle's chamber should be around 1.621. At this point my mild OCD kicked in, and I spent the next 90 minutes or so measuring every piece of brass, and the results explained a lot.
It turns out that after SAAMI FL sizing all of my brass, the head space measurement varied from 1.617-1.629. About 50% of the brass ranged from 1.617-1.622, and the remaining 50% was 1.625-1.629. For an additional confirmation, I tried chambering random cases from each cohort, and what do you know, the former chambered easily and the latter took mild to extra effort or wouldn't chamber at all, even after FL sizing. As a result, with a little trial and error adjusting the FL die and measuring with the comparator, I found that screwing the die about 1/4 turn or so deeper gets me at or under 1.621 for the pieces in the 1.625-1.629 range.
The next step is to lube and re-size all of the 1.625-1.629 cases and measure to make sure they're inside spec. for this rifle. They're obviously not all going to be perfect, but as long as they're under 1.622, they should chamber without issues. After firing, in the future I'll measure again to confirm they're 1.623ish in length, and then adjust the FL die appropriately for .002 bump.
To summarize, if you're buying fired brass or necking down brass from other rifles, make sure you are measuring not only OAL, but most importantly, the base to shoulder head space. This will eliminate issues chambering your reloaded ammo and hopefully mitigate waste and rework at the bench.