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    • #49330
      Larry Gibson
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      On another forum I was asked how well I could shoot the 30 XCB at 500 yards, particularly at a velocity of 2250 fps +/- having pushed the RPM Threshold up from 1940 fps.  It had been several years since I did any long range shooting with the XCB in a 10” twist and then the longest range was 300 yards.  Most of my LR shooting with the XCB in the 14” twist .308W Palma rifle and the 16” twist 30×60 XCB “DAWN” have been also limited to 300 yards. I did informally shoot out to 400 yards but nothing on record as such.  Time to do some 500 yard shooting on target.

       

      The cold weather front shifted a day earlier than expected so it cooperated this morning, February 26, 2018, at least for the 500 yard shooting. By the time I got to 600 yards the wind was switching back and forth from 5 o’clock to 9 o’clock and pushing 12 to 14 mph so I didn’t attempt shooting there at 600 yards with the 30×60 XCB in my rifle “DAWN”. I did however get fairly decent shooting conditions at 500 yards and got decent groups with my 10″ and 14″ twist .308Ws at 500 yards this morning.

      This morning dawned at 39 degrees with a 2 mph wind coming out of the SW. I was at my long range shooting local north of LHC about 30 minutes later. I set up the target and my wind flag and then went to the 500 yard firing point and set up a portable BR. It’s not the sturdiest bench in the world but it will do. From the firing point the wind was running 3 – 6 mph out of 7 to 8:30. By the time I was ready to shoot the sun was up and the temp was 45 degrees and the humidity 28%.

      The first rifle shot was my M1909 Argentine with a 24″ A&B barrel with a 10″ twist. It’s in a wood sporter stock. The scope is a 10X Weaver MicroTrac with friction adjustments. The load is the 30 XCB cast of #2 alloy and WQ’d, weight sorted as previously mentioned. The XCB was loaded in LC72 Match cases (match prepped of course) with WLR primers. The load I used, 44 gr RL22, is the same load that had proven extremely uniform and accurate at 2267 fps (163,224 RPM) in the thread I posted and suggested you read about how the RPM Threshold can be pushed up.  For calculating sight adjustment for elevation and the wind I used the “Applied Ballistics” program I got with Bryan Litz’s very fine book on long range ballistics.  That was really benificial because it got me pretty close elevation wise.  Also I had calculated the wind correction in moa and that was very helpful.  Before the shooting at 500 yards was done the wind was steady at 4 – 8 mps coming out of 8 o’clock.  That required 7 +/- moa (30 to 50” at 500 yards) adjustment for the wind with the 2267 fps load out of the 10” twist rifle.  I had put up a good wind flag which was very helpful as I tried to shoot in the same wind condition.

      I had set a rock about 6 – 8” I had painted black off to the side of the target to use as a “sighter”.  With the .308W rifle with 10” twist it took a bit to get on target at 500 yards with that older Weaver scope is friction, not click adjustable and the turret marks were not moa. I did manage to get the 10 test shots on target before I ran out of ammo…..barely.  The group was not centered up on the target. Here’s the rifle on the bench (sorry, no slick video as I’m so like last century….just some pictures and on target results)……if you save that picture to a file you can enlarge it and see the target and range flag on the face of that far ridge where the barrel is pointed.

      Here’s the target. Note two of the shots creased the edge of the target frame so I counted them in the group. Here’s the target measurement. It is an 11 3/4″ ten consecutive shot group at 500 yards. I covered the bottom bullet hole up with the tape taking the picture. However you can see it in the other photo. The HV load (for a 10″ twist) is holding very close to 2 moa (actually 2.35 moa) at 500 yards. Obviously the RPM Threshold has been pushed up but yet is still manageable. In the 2nd picture you can see the range flag hanging limp.  Seemed like every time I went to check/change the target the wind died. Then as soon as I got back to the bench it started blowing again…..go figure……

      I then switched rifles to see what controlling the RPM by using a slower twist and boosting the velocity can do for us. The next test was with my Palma rifle with a 27.4″ light Palma S&L 14″ twist barrel in 308W on a M98 byf action. The load is the standard 2600 fps load I worked up several years ago. It is 47 gr AA4350 in Winchester cases with WLR primers. Again the NOE 30 XCB bullet was cast of #2 alloy and WQ’d. The Lube was 2500+ and GCs are Hornady’s. With the 14″ twist 2600 fps is 133,714 RPM, considerably less than with the 10″ twist at 335 fps less velocity. The Palma load is well under it’s RPM threshold.

      Here’s the 500 yard 10 shot group from the Palma rifle at 2600 fps. With the precise elevation/windage adjustments of the Weaver T-16 on the rifle it didn’t take long to get centered on target.  Still I was using 4 +/- moa of wind adjustment.

      Here is the group measurement. The 10 shot group at 500 yards is 7 3/4″ which is 1.45 moa.

      So, there are the 500 yard 30 XCB test results that was asked for. This was a lot of fun for sure and I’m watching the weather forecast for the next low wind day.  Then I’ll be off again with DAWN to shoot at 600 yards……..

       

      Larry Gibson

    • #49345
      Artful
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      Nice report – supposed to camping this weekend up by flagstaff winds 23 mph -ugh

    • #49370
      popper
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      Good test & results.

    • #49387
      kens
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      Good test and results.

      You mentioned you have a 16″? twist gun, Dawn??

      With that at 500yards, does the groups get tighter such as the examples above?

    • #49421
      Darren McCann
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      Good morning,

      Larry those are some excellent results! I can’t wait to see what “Dawn” can do at 600…

      Darren

       

    • #49432
      Larry Gibson
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      Wednesday the 7th is supposed to be light winds….we shall see.

    • #49460
      Goodsteel
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      Excellent shooting Larry. More nails in the coffin.

      I am very interested to see the results you post with DAWN. That’s when we cue the music.

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