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<blockquote data-quote="bfoster" data-source="post: 1450779" data-attributes="member: 85">This problem is often caused by the glint of ambient light on the bullet. A fabric diffuser can often be helpful. Line up the chronograph first- get a reading to prove its aligned.Form a &quot;tunnel&quot; as follows:Push 4 pieces of 5&#039; long 1/2&quot; emt (electrical conduit) into the ground in a (roughly) 24 X 68&quot; rectanglular pattern with the chronograph screens in the center. The long axis (68&quot;) is aligned with the shooting position and the target, the chronograph is more or less centered on the 24&quot; dimension. Connect the top of each pair of poles on the long axis with a 3/8 X 1 1/2 72&quot; lath. I now use bolts to make this connection, but for years simply used zip ties. If it&#039;s a windy day you&#039;ll also have to brace the 24&quot; dimension near the top. Drape a piece of mosquito netting or other very, very sheer, matte fabric about 72 X 72&quot; over the lathing . Gather the corners of the fabric and zip tie one corner to each pole. This takes only a few minutes to erect with practice.Comments:1.&nbsp; &nbsp;&nbsp; Shadowrider&#039;s comment about making sure that you&#039;ve got enough distance between the muzzle and the first screen is important. Blast can cause severe problems.2.&nbsp; &nbsp;&nbsp; Blitzfike&#039;s comment about the source of the lighting is also relevent.The use of a diffusion tunnel is often helpful here.3.&nbsp; &nbsp; Oehler&#039;s chronographs use 3 screens-channels 1 &amp; 2 are compared with channels 2&nbsp; &amp; 3.&nbsp; &nbsp;&nbsp; The chronograph reports the difference and will frequently &quot;catch&quot; this sort of problem.regards,Bob</blockquote>

[QUOTE="bfoster, post: 1450779, member: 85"] This problem is often caused by the glint of ambient light on the bullet. A fabric diffuser can often be helpful. Line up the chronograph first- get a reading to prove its aligned. Form a "tunnel" as follows: Push 4 pieces of 5' long 1/2" emt (electrical conduit) into the ground in a (roughly) 24 X 68" rectanglular pattern with the chronograph screens in the center. The long axis (68") is aligned with the shooting position and the target, the chronograph is more or less centered on the 24" dimension. Connect the top of each pair of poles on the long axis with a 3/8 X 1 1/2 72" lath. I now use bolts to make this connection, but for years simply used zip ties. If it's a windy day you'll also have to brace the 24" dimension near the top. Drape a piece of mosquito netting or other very, very sheer, matte fabric about 72 X 72" over the lathing . Gather the corners of the fabric and zip tie one corner to each pole. This takes only a few minutes to erect with practice. Comments: 1. Shadowrider's comment about making sure that you've got enough distance between the muzzle and the first screen is important. Blast can cause severe problems. 2. Blitzfike's comment about the source of the lighting is also relevent.The use of a diffusion tunnel is often helpful here. 3. Oehler's chronographs use 3 screens-channels 1 & 2 are compared with channels 2 & 3. The chronograph reports the difference and will frequently "catch" this sort of problem. regards, Bob [/QUOTE]

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