Range Report OCW load development/7RemMag/175smk.H4831sc

Casey Simpson

Private
Full Member
Minuteman
Jan 2, 2008
18
2
59
Louisiana
<span style="font-size: 14pt"><span style="font-family: 'Times New Roman'">.284" bore 9" twist MTU fluted FTE brake chambered for 7m.m Remington Magnum. I like belts.
Printed 700, bedded into a Mac Htg. DBM bedded as well.
24x magnification. Prone ricesock.
Wind gusts to 20 from 12 switching from 10 to 2.
65-75'F 40%H2O. Naked bullets; Sierra 175smk. New Winchester cases. CCI Magnum primers. Lee dies.
Propellant Hodgon 4831sc. I like the way it feeds and it obviously works.
Elev. 2300'
I began by researching exhaustively propellants and charge weights by referring to online manuals and then personal experiences of other shooters, but knowing people make mistakes sharing information and lie too.
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<span style="color: #FF0000">First ten rounds fired. First round was in the berm but you see I walked it in. Restoring the bore after each shot fired. One grain of propellant distinguishes each shot from the other beginning at 60 grains. The purpose of this is to a.) discover the pressure limit of the barrel, b.) learn about vertical dispersion (ladder) while doing a, both while breaking in the bore. I dropped down three grains from barrel max being a small degree of twisting marks of the bolt face against the case head without difficult extraction. The last shot is the one a moa to the right of the group which could have been wind.
100 yards</span>

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<span style="color: #3333FF">Target on the left shows Optimal Charge Weight to be 67.8 but I like halves so I went with 67.5. These groups were fired round robin method at points of aim in black and with the charges written above the corresponding poa.
These groups on the target on the left were fired at a range of 100yards.

Target on the right shows the groups fired changing only seating depth by .010" per 3shot group and shows the optimal seating depth to be -50 thousandths of an inch (jump). Read left to right, top row first. These groups were fired at a range of 200 yards.</span>
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<span style="color: #009900">This picture represents the 100 yard poi using the 200 yard zero on the gray target. POA is the corner of the major orange @1.5" below poi. This load would have been the one fired at the last black dot poa on the gray target but since the first group on the lower row was obviously the sweet spot I used the .008" load here so I could later, using software, predict my load's velocity using data of known trajectory. I shot my chronograph and have yet to replace it.</span>
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<span style="font-weight: bold">Conclusion.</span>
<span style="text-decoration: underline">On this day</span> and under atmospheric and other conditions <span style="text-decoration: underline">this day</span> this test declares the Optimal Charge Weight of the propellant H4831sc to be 67.5 grains and the Optimal seating depth to be fifty thousandths of an inch off the lands.

I will continue to tweak if future firings either suggest its necessary or I won't if they confirm this test finding. Know one, first test is not conclusive, but suggestive only. Keep shooting it to find out.