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i've picked up some Hornady 100 gr. GMX bullets to try. I've never loaded solid copper bullets before so the question is:
Can 100 gr. monolithic bullets not be driven as fast as jacketed lead of the same weight?
i've stayed within Hodgdon loading specs but max velocity i can get without pressure signs is only about 2500 FPS out of my 18" Bison. Also another question:
I'm guessing higher velocities aren't needed as the bullet retains 100% (or near) of it's weight and therefore performs better?
accuracy seems to hover around 1.5 MOA at this point. I've used A2200, H4198 and H322.
O.K. guys, please educate me. :)
 

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moboy56, to start the discussion it would be best to have the specifics of your load data. Powder, Powder charge, primer, brass manufacturer (new, once-fired, multi-fired), shoulder setback, and COAL plus distance from the lands. How did you determine pressure signs: swipes, flatten primers, cratered firing pin dimple?

I have not loaded a lot of GMX in the 6.8 but was achieving at least 300 fps more with AA2200. However, I was loading 0.050" off the lands at 2.4" COAL. The velocity you achieved is about the same as Hornady's production Full Bore 100 GMX.

A "copper" bullet is longer than a lead-core because it takes 20% more copper to achieve the same weight. Thus a longer bullet (copper) at the same weight means less case capacity and more pressure for the same powder change. The bands on copper bullets reduce the engraving force as the bullet enters the lands but most companies recommend keeping copper bullets 0.050" off the lands to reduce chamber pressure spikes.

more later
 
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