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Old May 11, 2019, 04:44 PM   #7
Join Date: March 4, 2005
Location: Ohio
Posts: 17,932
CAUTION: The following post includes loading data suggestions beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assumes any liability for any damage or injury resulting from the use of this information.

When I wrote: "Hornady shows 2.090" COL for the FMJ and 2.210" for the IB," this was for identical powder charges in Hornady's book. One of the limitations is that Hornady steps velocity up in evenly spaced blocks and some of their bullets will be getting closer to the velocity claimed for a charge weight than others. Going from 2.09" to 2.235" increases the difference to 0.145", but the Hornady 150 grain FMJ is 0.178" shorter than the IB, so you actually have more space in the case with the 150-grain FMJ at 2.090" than you do with the IB at 2.235". As a result, the case has almost 0.6 grains more water capacity under the bullet when loading the FMJ to that shorter COL than the IB does at its longer COL.

Using QuickLOAD to make a comparison, it turns out you need about 2% more powder with the shorter FMJ bullet loaded to that shorter COL than you do with the IB loaded to Hodgdon's COL. So you would multiply all the Hodgdon charges by 1.02 from start to top to compensate for the using shorter bullet even at 2.090". With most of the supersonic velocity loads, it'll be around 0.3 grains higher charge weights. Not a lot.
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