Why do I need so much powder?

freddiej

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Since I have not seen this put out, here is what I am pretty sure is part of the answer.
new barrels are rougher unless they are hand lapped from the factory. if you have 100 FPS faster and take a bit more powder to give the same pressure and velocity then your barrel has burnished in and is slicker than it came from the factory. I learned this from my own experience. once my barrels were bunished (shot in) they had lower pressure, lower velocities, and took a bit more powder to bring them back to what I was used to. this could be part or most of your answer.
 

Huntnful

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Since I have not seen this put out, here is what I am pretty sure is part of the answer.
new barrels are rougher unless they are hand lapped from the factory. if you have 100 FPS faster and take a bit more powder to give the same pressure and velocity then your barrel has burnished in and is slicker than it came from the factory. I learned this from my own experience. once my barrels were bunished (shot in) they had lower pressure, lower velocities, and took a bit more powder to bring them back to what I was used to. this could be part or most of your answer.
That would make sense if it’s the case. I mean every round for the last 200 rounds just takes more powder than the 1st hundred. Still shoots excellent and super easy to develop a load for.
 

Stammster

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Same scale? Did your scale walk? Have you verified with a know test weight?

If it’s not a scale issue, I’m going with slower lot(s) of powder. The first lot of RL26 that I developed loads with was noticeably faster than the last 3 lots I’ve tried. So much so, that I’ve reached max case capacity and extremely compressed loads with the new lots - and still can’t get back to the original lot velocity.
 

Stammster

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Since I have not seen this put out, here is what I am pretty sure is part of the answer.
new barrels are rougher unless they are hand lapped from the factory. if you have 100 FPS faster and take a bit more powder to give the same pressure and velocity then your barrel has burnished in and is slicker than it came from the factory. I learned this from my own experience. once my barrels were bunished (shot in) they had lower pressure, lower velocities, and took a bit more powder to bring them back to what I was used to. this could be part or most of your answer.

That would make sense if it’s the case. I mean every round for the last 200 rounds just takes more powder than the 1st hundred. Still shoots excellent and super easy to develop a load for.

>>>>

My experience is the opposite. As the barrel breaks in, it speeds up - and less powder is required.
 

Jud96

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In my experience barrels only speed up when broke in if they speed up at all. I’ve never seen a load and/or barrel slow down that much in a mere 200 rounds. I think something has to be off like the chrono, powder scale, or the barrel has eroded A LOT. I have seen 50fps changes and like 0.5gr powder charge changes but never anything this extreme. I’m generally curious and concerned.
 

NielsC

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Check your OAL of the cartridge. You could be seating deeper or as previously stated have erosion. What does the chrono say?
 

Huntnful

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In my experience barrels only speed up when broke in if they speed up at all. I’ve never seen a load and/or barrel slow down that much in a mere 200 rounds. I think something has to be off like the chrono, powder scale, or the barrel has eroded A LOT. I have seen 50fps changes and like 0.5gr powder charge changes but never anything this extreme. I’m generally curious and concerned.
I’m curious as well, but not so much concerned. The pressures aren’t anything crazy.

But what I may do, is confirm a load with this batch of powder that I’m currently using, and then open up a separate brand new 1lber and see how much powder it takes to reach similar velocities. Could be throat erosion, but I just shot a 6” group at 1120 yards the other day. The rifle still hammers
 

Bob Wright

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How many rounds of Peterson brass did you start with?
The reason I ask is if they're work hardening, you might look at annealing them. Try one thing at a time of course.
They were annealed when you got them, so that becomes a variable if you had 100 of them and shot them 3x.
All the other comments are valid as well. Pick one and try...
 

Huntnful

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How many rounds of Peterson brass did you start with?
The reason I ask is if they're work hardening, you might look at annealing them. Try one thing at a time of course.
They were annealed when you got them, so that becomes a variable if you had 100 of them and shot them 3x.
All the other comments are valid as well. Pick one and try...
Yes sir! I’m just working my way down the list!

I actually started with ADG. And just recently tried Peterson for the last 30. All virgin brass. Still takes 87.5 gr to be near pressure with a 180 hybrid berger.
 

Wedgy

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N570 will erode the throat about 35% faster than H1000, speed comes with a price. Clean it thoroughly and measure erosion if you didn't already. It sounds like the new lot of N570 is slower than the old stuff but you mixed it 50/50 so that should have cut the decrease by 50% and it is still significant so it must be a combination of things. BTW painters call this "boxing the paint" where they mix several gallons together so it is one batch of uniform paint.
As stated the lead time on build components is pushing 8 months to a year(more if you want a custom fast twist barrel) so if you want something for 2022 season you had better get it in the mix soon.
That rifle hammers though regardless of what is going on !
 

Bob Wright

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Yes sir! I’m just working my way down the list!

I actually started with ADG. And just recently tried Peterson for the last 30. All virgin brass. Still takes 87.5 gr to be near pressure with a 180 hybrid berger.
I'll throw this in then. Fireforming that first time will drop pressure the second time. It would make sense to me, that part of your velocity drop can be attributed to increased volume in the case even after FL sizing.
Same as not using your pet load with old brass, when using brand new brass. You naturally back off with virgin brass and work back up with 1x or more fired brass. Just one more thing you might consider.
 

Jud96

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Yes sir! I’m just working my way down the list!

I actually started with ADG. And just recently tried Peterson for the last 30. All virgin brass. Still takes 87.5 gr to be near pressure with a 180 hybrid berger.
So do you have to add more powder with ADG to get the same speed as before or did you just try Peterson and have to add powder to get the same speed as ADG?
 
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