Everyone, first off, I want to remind everyone on the importance of inspection of brass. Long story short, I am trying to see what everyone's thoughts are on a really high FPS on my chrony.
So I had some brass I was fireforming for my 7-30 waters. A friend had given me 19 rounds of 30-30 brass. He wanted to make it an even 20 so he threw in one 32 Special case. I had to do a little research, but fourn that 32 sp is a rifle round that is basically a necked up 30-30 brass. So I guess he figured it would be ok to neck it back down to 7 mm.
Load - 38 gr. of W748 and a 100 gr. Sierra BTHP.. Most of the loads were doing 1500-1700 fps. But then, I got one that showed 5181 FPS on the chrony. I first suspected that the chrony was way off. It is a Competition Electronics ProChrono.
After inspecting the case , I discovered it was the 32 SP headstamp. I also noticed that the rim is a little different than both my 30-30 headstamps and the few 7-30 headstamps.
But my main suspicion as to the cause is the case length. I measured it at 2.04, which is the max according to my manual. All the other brass I have is just slightly shorter. So my thought is the excessive length caused the case to "crimp " down on the bullet in the chamber , causing much higher pressure. I don't think the primer shows any signs , nor any other signs of high pressure.
So I am trashing this one case and will definitely be checking my case length closely. I have since had my lee case gauge for 7-30 arrive.
See the pic and let me know what your thoughts are??? It is the case on the Left.
So I had some brass I was fireforming for my 7-30 waters. A friend had given me 19 rounds of 30-30 brass. He wanted to make it an even 20 so he threw in one 32 Special case. I had to do a little research, but fourn that 32 sp is a rifle round that is basically a necked up 30-30 brass. So I guess he figured it would be ok to neck it back down to 7 mm.
Load - 38 gr. of W748 and a 100 gr. Sierra BTHP.. Most of the loads were doing 1500-1700 fps. But then, I got one that showed 5181 FPS on the chrony. I first suspected that the chrony was way off. It is a Competition Electronics ProChrono.
After inspecting the case , I discovered it was the 32 SP headstamp. I also noticed that the rim is a little different than both my 30-30 headstamps and the few 7-30 headstamps.
But my main suspicion as to the cause is the case length. I measured it at 2.04, which is the max according to my manual. All the other brass I have is just slightly shorter. So my thought is the excessive length caused the case to "crimp " down on the bullet in the chamber , causing much higher pressure. I don't think the primer shows any signs , nor any other signs of high pressure.
So I am trashing this one case and will definitely be checking my case length closely. I have since had my lee case gauge for 7-30 arrive.
See the pic and let me know what your thoughts are??? It is the case on the Left.
