Compressed loads weren't compressed?

KDX

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I was reloading some 17 FB the other night. Hogdgon's site states (Benchmark with 20gr V-Max) to start at 18.5gr and 20.0 is the max with a compressed load. I started at 19.0 and loaded 5 each going up by .2gr increments to 20.0gr and when I got there the powder was still not into the neck which is what I would assume would be a compressed load. I'm using a RCBS Chargemaster Combo that gets calibrated at the beginning of the loading process so I would assume it is accurate. I haven't been out to try these loads so I have no idea as far as if there are any pressure signs on the stiffer loads. Any ideas or info would be appreciated.
 
I'm guessing that the original data from Hodgdon was compiled using a "lot" of Benchmark that was maybe a little less dense than what you have and possibly the kernels were a bit longer. I know they don't list which brass to use on their site so less case capacity in the one they used to test would also come into play. Out of curiosity, at what point would you have had a compressed load with your components ie: how close would you have been?
 
Lot's of things could be at play here, especially with a small cartridge such as that.

#1 would be brass. Are you using the same brand used by hodgdon? Small differences in dimensions become more apparent in small cases.

#2 different lot of powder.
 
Is your brass fire formed. The lyman manual has 20 grains benchmark also marked as a compressed load with the 20 grain v max. Your brass may have a slightly higher internal volume.
 
I haven't gotten there yet at 20.1gr. That is where I stopped. I haven't been to the range yet for some sighting in so I will be watching for pressure signs as I go through the different loads. I realize every rifle is different and has their own personality. The rifle I have is a Cooper Model 38 Classic.

edit to add...I posted before the last few posts and the brass I am using is brand new unfired Remington brass that had only been neck sized.
 
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