I fired off some mixed brass reloads in my M14 this weekend past. Now I'm finally trying to get a little serious about loading for the beast so I'm checking the headspace on the fired brass using an RCBS Precision Mic.
The IVI former 7.62 NATO brass mics up consistently at 1.6427inches . The RCBS Precision Mic instructions refer to .308 Win ANSI headspace should be between 1.6300 and 1.6400 inches.
Not particularly surprising that the Norinco would have a little slop in the chamber.
What's throwing me off is I also checked the headspace on some Federal (FC headstamp) brass from the same shooting session, also reloads, and I get a measured headspace of 1.6285 or slightly below the ANSI range.
This was the same rifle, same primers, same bullets, same full length sizing die, same powder, same reloading 'lot' by myself. This is at least the second time I've run these brass through my M14 as well.
I was expecting some delta between the two types of brass but not one over and one under the ANSI range.
I'm tempted to full length resize the IVI brass back into the ANSI range, effectively bumping the shoulder back about 12 thou, and just neck sizing the FC brass since it is already below the minimum.
I also plan to use the Precision Mic to better set my Redding full length sizing die. The last batch (i.e. these particular brass) resulted in some rounds that would not chamber in my other / bolt rifle. Every round fired consistently in the M14.
Anyone have any hints or insights re what's going on with these two different types of brass. Should they be that much different?
The IVI former 7.62 NATO brass mics up consistently at 1.6427inches . The RCBS Precision Mic instructions refer to .308 Win ANSI headspace should be between 1.6300 and 1.6400 inches.
Not particularly surprising that the Norinco would have a little slop in the chamber.
What's throwing me off is I also checked the headspace on some Federal (FC headstamp) brass from the same shooting session, also reloads, and I get a measured headspace of 1.6285 or slightly below the ANSI range.
This was the same rifle, same primers, same bullets, same full length sizing die, same powder, same reloading 'lot' by myself. This is at least the second time I've run these brass through my M14 as well.
I was expecting some delta between the two types of brass but not one over and one under the ANSI range.
I'm tempted to full length resize the IVI brass back into the ANSI range, effectively bumping the shoulder back about 12 thou, and just neck sizing the FC brass since it is already below the minimum.
I also plan to use the Precision Mic to better set my Redding full length sizing die. The last batch (i.e. these particular brass) resulted in some rounds that would not chamber in my other / bolt rifle. Every round fired consistently in the M14.
Anyone have any hints or insights re what's going on with these two different types of brass. Should they be that much different?
