200 straight rounds of Norma Mag

[Mike D Texas]

Oh yeah. They lose speeds as the throat erodes further and further away. But that’s normally from less pressure. I’ve never seen a speed loss, accompanied by higher pressures.

I started a load in my 28 nosler at 83gr. N570. When the barrel was shot out at 800 rounds I needed 87gr. N570 to produce the same speed. Same jug of powder.

Well I say speed loss because I had to back my loads down to higher pressure. I originally thought it was a carbon ring but I scrubbed the chamber throat area down to bare metal and it didn’t change significantly.


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[huntnful]

Well I say speed loss because I had to back my loads down to higher pressure. I originally thought it was a carbon ring but I scrubbed the chamber throat area down to bare metal and it didn’t change significantly.


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Oh weird. I’m not sure about that one. I’ve never seen that personally. Normally lose speed as the barrel wears out. Have to either seat bullets longer or add powder to chase it (or both)

 

[Mike D Texas]

I agree it’s weird. I did some reading and found mixed opinions on it. What I do know is that a proven load for hundreds of rounds suddenly started showing pressure signs and I had to back down a full 2 grains to keep it from happening.


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[Quicksilver]

My 300 Norma is slowing down, but I haven’t had to chase the velocity with more powder yet. It has tapered off 20-25fps but still seems to be happy.

 

[huntnful]

I agree it’s weird. I did some reading and found mixed opinions on it. What I do know is that a proven load for hundreds of rounds suddenly started showing pressure signs and I had to back down a full 2 grains to keep it from happening.


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That’s definitely weird. Not sure what would cause that honestly.

My 300 Norma is slowing down, but I haven’t had to chase the velocity with more powder yet. It has tapered off 20-25fps but still seems to be happy.

Yeah you definitely don’t HAVE to chase it. My accuracy’s never really dropped off because of it. Just an extra click or 2 on the turret haha