300 Blackout headspace issue...
Posted: 07 Apr 2014 14:32
So I have a friend that built himself a 300 AAC Blackout AR this winter. Its a great round, lots of fun and he and I have learned a lot from the build. Since this is a fairly new round (Only been SAAMI spec approved for a couple years or so), I got him the new 300 blackout dies from Lee for Christmas.
Of course, he has never done reloading, and has spent a small fortune to get setup to cut, form and load his own brass. (Merry Christmas, you're welcome LOL). This weekend we took several small batches of his reloads to the range to run them through my chrono and test them for function... which is where we found our first issue!
It seems that some NATO brass is a little bit thicker than others, and he ran into chambering issues with brass with the headstamp S&B from the Czech company Sellier and Bellot. The problem is that the 300 AAC is made by cutting the body off at the shoulders, then necking the body down to .308 and trimming to length. With the body of this particular brass being thicker, the OD on the neck would stretch out of spec when the bullet was pressed into place. Luckily, when it was ran into the chamber, it would not seat all the way, and jam the carrier group just out of battery... Luckily we never got far enough into it to actually set one off and have a really bad day.
He thought is was a problem with the die set, until I explained to him what was going on, and that he needed to check each headstamp type with his calipers to make sure that they are in spec. I figured I would throw this info out there in case there are any others beginning to load their own Blackout cartridges!
Of course, he has never done reloading, and has spent a small fortune to get setup to cut, form and load his own brass. (Merry Christmas, you're welcome LOL). This weekend we took several small batches of his reloads to the range to run them through my chrono and test them for function... which is where we found our first issue!
It seems that some NATO brass is a little bit thicker than others, and he ran into chambering issues with brass with the headstamp S&B from the Czech company Sellier and Bellot. The problem is that the 300 AAC is made by cutting the body off at the shoulders, then necking the body down to .308 and trimming to length. With the body of this particular brass being thicker, the OD on the neck would stretch out of spec when the bullet was pressed into place. Luckily, when it was ran into the chamber, it would not seat all the way, and jam the carrier group just out of battery... Luckily we never got far enough into it to actually set one off and have a really bad day.
He thought is was a problem with the die set, until I explained to him what was going on, and that he needed to check each headstamp type with his calipers to make sure that they are in spec. I figured I would throw this info out there in case there are any others beginning to load their own Blackout cartridges!