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A little observation or two from LR shooting yesterday...

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Unread 09-29-2008, 11:16 AM
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A little observation or two from LR shooting yesterday...

Got out and shot out to 1001 yds yesterday.

Interesting comparison on a 1/2" mild steel gong at 884yds between my brother's 300 WSM spitting 180 AB's at 3050 MV (Fed. Pre. Vital Shock) and my 300RUM launching 240 SMK's at 2995 MV (new 104.2g load with SMK's on the lands as switched FED215M primer lots and went to a new keg of US 869. I also use the + .010 Redding Comp. Shellholder to give about .002 push on the shoulder so it's not getting sized quite as much as a regular shellholder and between that and putting the 240 SMK on the lands I may get a bit more volume out of that case resulting in a load around or just over 104g US869 seeming comfortable.)

At 884 yds on the steel, the bonded AB's took the paint off, but that was about it. It was difficult to tell if any metal had been moved at all. The 240 SMK's were making 3/16" to 1/4" deep craters and bulging out the back of the plate, as usual, where they hit. I was surprised because even though the SMK is being launched at about 1K more energy at the muzzle, I thought the AB, being bonded and seeminly a tougher bullet, might make a similar impact. I was wrong. Obviously, with the higher SD of the 240 SMK and the much higher BC of the SMK, it's going to retain more energy and being launched at 1K ft. lbs. more energy to begin with must make the difference. Below is a shot of the gong with the 3-shot 240 SMK group from yesterday to the right and low and the 2 shots that hit the gong from the 180 AB with my fingers pointing at them. Perhaps in combination with the energy difference/SD difference is the fact that the AB are designed as an expanding bullet. Black circle is 3 1/4".

As you can see from previous shooting, my shots are often low and to the right at longer distances. Wind was calm or nearly calm yesteday and if there was any at all is would've been a sun caused uphill and Right to Left wind and still the low and right. Perhaps I need to play with Exbal's Coriolis effect (at about 48.5 lat and shooting about 45 deg off north) and spindrift calcs with a RH twist barrel?

I've put on a 20 MOA Seekins base a month ago and I'm not sure if this has an effect on some of what I saw yesterday because I've heard different opinons on this site as to the effect of slanted bases and Exbal predictions. Exbal predicted 6 MOA ele. at 434 yds. and 9 deg. Right on with the elevation, given the center of the group. At 884 yds, group center was approx. 1/2 MOA low. At 1001 yds. the group center was again approx. 1/2 MOA low although I nailed the bottom of the rock approx. 9" rock a couple of times out of five. I've typically been right on the ele. to 1000 yds with previous combination (with 0 MOA Farrell Pic base), so I'm wondering what the issue may be. Most likely it's me, as I'm typically the weak point in the system. Just curious if those folks that have shot alot more than me with slanted bases have found any similar results? Thanks, Jon.
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Last edited by jmden; 09-29-2008 at 01:16 PM.
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