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Same velocity less signs of pressure?


Ihrtuspsa
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So I have two different types of loads I use now one with the most recent bullet I have talked about on this form 124 grain Berry's Hollow base Flat Point thick plate and 124 grain round nose Full Metal Jacket. I notice with the same grain weight 7.8 to 7.9 of hs-6 I get about the same velocities between these two bullets but the hollow base Flat Point shows zero flattening of the primers compared to the 124 grain round nose that definitely shows flattening. Both are loaded to 7.8 to 7.9 grains of hs-6 and both are around the same velocity of 1360 feet per second on average but with the round nose Full Metal Jacket there is a little primer flattening where there is absolutely none with the Berry's Hollow base Flat Point. Can anybody explain why this is?

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I'd guess that the hollow base effectively makes a larger volume for the powder to start building pressure in, while the FMJ makes a lesser volume. 

 

Same as seating a bullet deeper increases pressure, the hollow base DECREASES pressure, as opposed to the FMJ.  

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What OAL are you loading them to?

 

Keep in mind that the hollow base, by itself, does not create more internal volume in the powder chamber. Let me explain. Let's say you have two bullets of the same weight and the same shape, e.g. both round nose, and one has a hollow base and the other is solid. The hollow base bullet is longer because lead has been taken out of the middle of the base and moved to the side of the bullet. If you seat them to the same OAL, the available space in the case is the same.  The hollow base merely changes the shape of the powder chamber, not the volume. 

 

Whether it does in your case, since your bullets are different shapes (FP, RN) is hard to say without more information.  

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It's the thick plate.  And I settled on 1.10. These have been the most consistent pal bullet when seating I have ever come across. Accuracy is noticeably better than round nose too.  Also the hole it punches in cardboard is way cleaner and almost always perfectly symmetrical. This is my new favorite. Today using my new chrony chronograph I was getting 1360fps with 7.8 gr hs6 pal 1.10. Tonight I loaded a batch to 7.9 and 8.0 gr hs6 tomorrow will chrono again. 

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